Relieving Engine Bay temps - ventilation

[FNQGU]

Can anyone point me in the right direction to threads touching on the above topic or give me a few hints on how to best lower my engine bay temps?

Do I need to consider a bigger scoop?

I was just advised to get a nice big wide scoop and only use half of the scoop with the Intercooler, and the other half to simply pump air through the engine bay and out the bottom. Or to fit a second scoop for the same reason.

Does that make sense to those of you who know or is it BS?

[Clunk]

Doggy may or may not know........... can't remember if he has an intercooler but he does have 2 scoops

[the evil twin]

Can anyone point me in the right direction to threads touching on the above topic or give me a few hints on how to best lower my engine bay temps?

Do I need to consider a bigger scoop?

I was just advised to get a nice big wide scoop and only use half of the scoop with the Intercooler, and the other half to simply pump air through the engine bay and out the bottom. Or to fit a second scoop for the same reason.

Does that make sense to those of you who know or is it BS?

My call is... What a load of bollocks.

The more air you pump into the engine bay the less air travels thru the radiator.
Thats why the 'engineers' spec out things like radiator shrouds, air diverters, rubber flaps along the guards to the chassis etc when they design a vehicle.
As well as that scoops will have no effect at low speed, in traffic or gnarly 4X4 work.

About the only thing I would give any credence to is raising the rear of the bonnet slightly but when you look at the size of the escape down past the engine will a slit less than 1/2 an inch high and a couple of feet long make much difference

[Sherro]

You could always try a turbo blanket and exhaust wrap it works for me, i just replaced my old exhaust for a bigger one and after three years being wrapped there was no rust under the rap.

[the evil twin]

You could always try a turbo blanket and exhaust wrap it works for me, i just replaced my old exhaust for a bigger one and after three years being wrapped there was no rust under the rap.

Yeah, good point Sherro, my 6.5 is wrapped and Brunnies are real keen that they should be kept that way

[the evil twin]

Doggy may or may not know........... can't remember if he has an intercooler but he does have 2 scoops

His has two scoops 'cause the prev owner to the prev owner did it to look pretty.
At the time Krittas owned it and it was wrung to within an inch of it's life turning 35's and putting out serious grunt.
I only had it for a relatively short period and got the pump wound down a bit, kept the 35's and big lift on it but IMHO the twin scoops were pretty much only cosmetic.
Doggy has detuned it a tad more but he has also had it waay longer than me and may have a different view on the scoops

[kevin07]

I put a bigger scoop on and get about 50 lower temps

[Clunk]

His has two scoops 'cause the prev owner to the prev owner did it to look pretty.
At the time Krittas owned it and it was wrung to within an inch of it's life turning 35's and putting out serious grunt.
I only had it for a relatively short period and got the pump wound down a bit, kept the 35's and big lift on it but IMHO the twin scoops were pretty much only cosmetic.
Doggy has detuned it a tad more but he has also had it waay longer than me and may have a different view on the scoops


ahhhhhhhhh I see

[FNQGU]

I have the same exhaust wrap from Brunswick Diesels, but no thermo cover (blanket) on the turbo. I might look at doing that.

When you say raise the rear of the bonnet, do you mean simply putting a couple of washers or spacers underneath the bonnet hinge bolts to raise it up a fraction to let air out the back edge of the bonnet?

@Kevin07 - are you referring to one of the ARE bonnet scoops or similar? And this lowered your general engine bay temps by 50 degrees? That sounds like a worthwhile modification if that is the case.

[Clunk]

When you say raise the rear of the bonnet, do you mean simply putting a couple of washers or spacers underneath the bonnet hinge bolts to raise it up a fraction to let air out the back edge of the bonnet?


I believe so yes......... has been done on my TD42 by the previous owner, I've got no idea if it helps or not but cant be arsed to remove them to find out if they do lol

[Avo]

I use to own a hilux with a 253 in it and use to battle the temps often.i put 2 of these in with the scoop(caravan vents) bits facing backwards(1 each left and right of the bonnet) so the air could exit the engine bay..worked well..kept temps down to about quarter on the guage.
http://www.ebay.com.au/itm/CAMEC-016518-Aluminium-Lourve-Vent-150mm-x-300mm-Caravan-Motorhome-Camping-RV/321628518021?_trksid=p2054897.c100204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D20140407115239%26meid%3Ddd294c1043544f77bc4 4695537d8254a%26pid%3D100204%26rk%3D23%26rkt%3D30% 26sd%3D231435835615

[threedogs]

you could also jet coat the manifold and dump pipe, inside and out
Keep the temp inside the pipe

[Gecko17]

Mine is the same as ET's, all wrapped up but it was still getting so hot under the bonnet, when I went to pump up my tyres, from the air pump under the bonnet, the thermal cutout kept kicking in after only about 10 mins....

I ended up putting in two marine vents on either side of the top of the bonnet....worked a treat and hasn't overheated since. (will put up a pic when I get home from site...)

[threedogs]

XA Ford GT bonnet scoops might work ok
I dont think it legal to have rear facing hood scoops.
Cause if you break a hose your vision will be impaired

[FNQGU]

you could also jet coat the manifold and dump pipe, inside and out
Keep the temp inside the pipe

Yes, definitely another option and why I was interested in Cuppa's recent playing around with ceramic coatings.

I do like the sound of those small marine type vents Gecko and am keen to see a pic of that.

Might try a combination of some of the above suggestions and see what happens. Better ventilation seems key, then keeping the heat down and out the exhaust too.

[threedogs]

Hotrods have small 9" fans to draw heat out of the engine bay but where you put them i have not idea.
How do you or why do you think you have heat block

[the evil twin]

Geck and wa are the best ideas IMHO... help the air travelling thru get out and also stop any stratification IE a layer of really hot air up against the bonnet more so than try and force more air in.
As prev mentioned, raising the rear of the bonnet on the hinge adjstments or mounts is another but looks a bit poo IMHO

[threedogs]

I was forever this problem with my 350 chev 75s Troopy, after jet coating my blockhuggers inside and out
lifting the back of my bonnet,Plus installing two GU bonnets scoops , and countless radiator up grades, I figured it out ,
Faulty VDO temp guage.lol brand new too,
I drove home from the Murray in 45 degree heat sitting on 110kph and with the new gauge temp was spot on the whole time
Just spewing it cost me so much searching for solutions

[kevin07]

I have the same exhaust wrap from Brunswick Diesels, but no thermo cover (blanket) on the turbo. I might look at doing that.

When you say raise the rear of the bonnet, do you mean simply putting a couple of washers or spacers underneath the bonnet hinge bolts to raise it up a fraction to let air out the back edge of the bonnet?

@Kevin07 - are you referring to one of the ARE bonnet scoops or similar? And this lowered your general engine bay temps by 50 degrees? That sounds like a worthwhile modification if that is the case.
sorry that's egts but I suppose the engine bay would have been cooler as well how much nfi

[Gecko17]

Here are the marine vents that I cut into the bonnet. Has worked a treat. There are different styles but I went with these.


Sent from my iPad using Tapatalk HD

[Ben-e-boy]

Bite the bullet and get some ceramic coating,
Its not that expensive really, mine is getting, done at the moment
I'll get change from a grand coating the pistons, combustion face (including the base of the valves) the pre combustion chambers inside and out, inside the exhaust runners, the exhaust manifold inside and out, the turbine housing inside and out and the dump pipe inside and out.

Thats a lot of ceramic for less than a grand.

[Hodge]

Speaking of under the hood tempereatures... I never understood or liked top mount intercoolers and bonnet scoops.
Common law of physics, heat rises and attempts to escape upwards. So here we have air being pushed, through the front of the engine bay, through the radiator, cooling it down, over the fan onto the engine and then the hot air tries to go up, through the IC and bonnet scoop ?? But then you have the cold counter-air being pushed downwards through the bonnet and IC, and you have a result of 2 clashing air fronts.

Ultimate is front mounted cooler, with exit points as far back on top of the bonnet as possible.

[liftlid]

Speaking of under the hood tempereatures... I never understood or liked top mount intercoolers and bonnet scoops. Common law of physics, heat rises and attempts to escape upwards. So here we have air being pushed, through the front of the engine bay, through the radiator, cooling it down, over the fan onto the engine and then the hot air tries to go up, through the IC and bonnet scoop ?? But then you have the cold counter-air being pushed downwards through the bonnet and IC, and you have a result of 2 clashing air fronts. Ultimate is front mounted cooler, with exit points as far back on top of the bonnet as possible.
Bring your ft mount inter cooler muddy Victoria and you will change your mind, they get hot enough after a mud run with a top mount intercooler without putting something else in ft of the radiator

[AB]

Bring your ft mount inter cooler muddy Victoria and you will change your mind, they get hot enough after a mud run with a top mount intercooler without putting something else in ft of the radiator

Challenge accepted ;)

I've already won a $100 off my bro, pending payment!!!!!

[Winnie]

Challenge accepted ;)

I've already won a $100 off my bro, pending payment!!!!!

Dude you're never going to see that $100 dollars. Haha he'll always add more conditions
Especially if he hears that you want to upgrade your radiator! Hahahaha

[the evil twin]

Bring your ft mount inter cooler muddy Victoria and you will change your mind, they get hot enough after a mud run with a top mount intercooler without putting something else in ft of the radiator


Challenge accepted ;)

I've already won a $100 off my bro, pending payment!!!!!

... are you the same AB that is asking if a bigger water pump is worth trying in order to address your overheating issues?

[AB]

... are you the same AB that is asking if a bigger water pump is worth trying in order to address your overheating issues?

The overheating issues are totally not related to my intercooler old mate ;)

Yep, I'm a stubborn young buck but i will prevail...

Just towing heavy loads and fully loaded in hot and humid weather caused slight increase in temp, nothing new with these old beasts mate...non towing is a dream, easy money ;)

Had it caked in mud before, all good :)

[the evil twin]

The overheating issues are totally not related to my intercooler old mate ;)



Ziiiiiiiiinnnnnnnnnnnnnnnnnnnnnnnggggggggggggggggg ggggggggggggggggggggggggggggg, Fish on, Fish on...

ROFL, Hiya mate,

Why dont'cha try one of them, there, new fangled 'lektric pumps like in the other thread or even better nip down to Onga and grab a 4 HP Fire Fighting jobbie?

Sorry, for the hijack, I just got back from a few days field work and I think the heatwave temps over here have fried my brain, I'll stop now... maybe...

[threedogs]

what is the main concern getting cool air in or letting hot air out.
We should all put an oven thermometer under
the bonnet and see what the results are.
Sounds like a fair test, If everyone takes the temp near the start battery
we should get some decent data that way.

@ hodge I'll point my thermo gun in my scoop at the intercooler
as soon as I turn it off and see what temps are

Whats a crittical temp for the AUX battery

[threedogs]

http://www.ebay.com.au/itm/TURBO-BLANKET-T4-HEAT-SHIELD-COVER-BEANIE-T4-GT40-GT42-GT55-T66-T67-T76-T4BK-/131290940973?pt=AU_Car_Parts_Accessories&hash=item1e918cc62d

Found this but might be only good for the 3ltr boys

what size turbo do the 3ltrs have STD?

[FNQGU]

Gecko - I do like the look of those vents, and was thinking of that exact same spot after looking at the bonnet closely.

As a bit of an update - I put one of those turbo blankets on, and took off for a good long run up to Ravenshoe and Herberton, then off-road to some steep climbs and nearly fried the engine I reckon. Something is wrong as temps are rising and rising when under load. On the highway climbing up through the range into Herberton, it quickly got to 105 celcius before I pulled over and let it cool. Off-road in low-range temps got to 110 celcius at the top thermostat bolt. They would slowly drop back to normal (85 celcius) when I pulled up, lifted the bonnet and let it idle. Freaked me out actually and put an end to testing. We camped up for the night and I babied it home this morning with temps only getting into the mid 90's before I'd pull up and let it cool down. Temps also stayed lower with the aircon offf.

Now got to find the problem.

Radiator fluids are good and there are bugger all bugs or grass seeds in it.

The viscous coupling on the radiator fan could be an issue. I can easily turn the fan by hand.

About to pull the thermostat and make sure it is working properly.

Ceramic coating the dump pipe and turbo could well be an option but I've had this truck purring like a kitten for the best part of the last 2 years and never had any hint of overheating issues, so I am convinced something has recently gone wrong.

The only thing recently changed was the tranny cooler position, however there should still be sufficient air getting to the radiator. I haven't removed this as part of the problem yet though. Tranny fluid temps were beaut the whole time.

Any suggestions will be gratefully welcomed.

[the evil twin]

Uuuuummmm... 110 at the thermostat bolt doesn't necessarily equate to an issue or directly to coolant temps, engine operating temp etc.
Coolant can only take heat away from something that is hotter so it is a matter of determining if the coolant is heating the thermostat housing or is it heat soak.

What was the factory gauge showing at the time?

I do agree the viscous clutch is knackered by the sound of it.

[FNQGU]

Factory gauge went to 4/5ths and was rising when I pulled up. I agree with you but I have never seen it anywhere near that sort of gauge reading before. 110c seems on the high side to me and I'm not comfortable with it.

I couldn't find any leakage on the viscous coupling, but I can spin it with one finger. I couldn't do that before so will pull it out on Monday and see what happens after that.

Re general engine bay temp - the whole area seems hotter than normal at the moment. The intercooler was almost too hot to touch, so can't be of much value in reducing charge air temps, probably making air temps hotter if anything.

[threedogs]

@ FNQGU so you reckon those turbo beanies[thermal cover] are no good ??

[FNQGU]

Sorry for the delay - been out for a bit.

Well, my viscous coupling was Roo-Ted by the looks of it and would appear to have been causing my engine bay temp issues recently. As I understand them, when they are cold they spin freely, and when they heat up they get harder and harder to turn and even lock up to run 1:1 with the engine? Well, mine must have had a leak at some stage, and there was none of that viscous fluid left in it to kick in and spin the fan when hot. I could turn it with one finger. Have ordered a replacement and am hoping this makes a difference but it has got me looking into engine bay temp management and what is normal and acceptable and what is not. I was also recommended to forget the viscous coupling and simply bolt up direct so the fan always runs in a 1:1 ratio to the engine (?). I am still pondering this, as yes it might be more efficient in dragging air through the radiator, but what happens when crossing deep water for instance?

TD - my turbo cover made SFA discernible difference under the circumstances, but I suspect that my overheating issue outweighed the benefits and I hadn't set up any testing gear to try and measure it either. I might play with that a bit in the future, but anything that diverts heat back down the dump pipe has to be a good thing, and it certainly seems to work as I can touch the outside of the cover without burning my fingers.

From a previous post by Old Mav, who would know, it seems that very little can effectively be done as air-cooling an engine bay is not really an efficient way to go unless traveling at speed. That said, there does appear to be a lot of info in the race car scene indicating that bonnet venting can have measurable benefits in managing engine bay heat, and this could apply to 4wdriving speeds. Ceramic coatings and turbo blankets are a very effective starting measure it appears.

The analogy of comparing an open umbrella, or a cardboard box with one end open, to driving an engine bay through the air seems to be used a bit. It is all about high pressures and low pressures, and allowing air to flow freely out of an engine bay without detrimentally affecting flow through the radiator as a result.

The below articles also shed some further light, and I do like the articles from Autospeed:
http://www.speedcafe.com/2012/03/23/bonnet-vents-introduced-into-v8-supertourers
http://www.autospeed.com/cms/article.html?&A=2159
http://www.autospeed.com/cms/article.html?&A=2160
http://www.autospeed.com/cms/article.html?&A=2162
http://www.autospeed.com/cms/A_2455/article.html
http://www.autospeed.com/cms/A_2456/article.html
http://www.torquecars.com/tuning/exhaust-wraps.php
http://www.hoodlouvers.com/racinghigh-performance/

One thing I noticed during my heat issue, is that my Intercooler is getting seriously affected by engine heat-soak to the point where I doubt very much it is actually cooling any of the charge air, rather is probably doing the opposite if anything. With this in mind, I spoke to ARE about their more aggressive bonnet scoops, and the feeling was that the increased air-flow through the scoop would help in combating the heat-soak issue, however that is not really the intent, as the air should be dragging heat out of the intercooler core down into the engine bay, and perhaps even slightly adding to the heat management issue. At low speeds, a fan beneath the intercooler would have definite benefits. At higher speeds they didn't think so, in fact they thought the fans then became a hindrance.

Lots of food for thought in this area of heat dissipation and aero-dynamics...

[threedogs]

Why not fit a 9" fan under a second scoop to remove heat when travelling slow.
It could be set to come on at a certain temp, as stated usless if travelling
heat rises so GKO's vents seem to look like they would suck heat out at speed.
would a wider scoop help?
http://www.ebay.com.au/itm/Toyota-Land-cruiser-Nissan-Patrol-Bonnet-Scoop-500mm-wide-/121533197233?pt=AU_Car_Parts_Accessories&hash=item1c4bf16bb1

http://www.ebay.com.au/itm/XB-BONNET-SCOOPS-SUITS-GT-GS-FAIRMONT-COUPE-SEDAN-ETC-EXCELLENT-CONDITION-/251815997523?pt=AU_Car_Parts_Accessories&hash=item3aa1673053
These would lookawesome either side of your scoop on a custom bonnet

Just remembered on my 75s Troopy and some early Range Rovers they had vents on the side of the guards , they were
mainly to keep the battery cool, maybe it would work on a GU as well

http://www.ebay.com.au/itm/BONNET-VENTS-1-PAIR-NEW-ITEM-HOOD-SCOOPS-universal/331300676755?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D20140106155344%26meid%3D8fb5b22440f0425482f a2c2db8aee54c%26pid%3D100005%26rk%3D1%26rkt%3D6%26 sd%3D231315776421&rt=nc

http://www.ebay.com.au/itm/BONNET-VENTS-IDEAL-FOR-REDUCING-UNDER-BONNET-HEAT-ON-FOUR-WHEEL-DRIVES/251812234737?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D20140106155344%26meid%3D8fb5b22440f0425482f a2c2db8aee54c%26pid%3D100005%26rk%3D2%26rkt%3D6%26 sd%3D231315776421&rt=nc

[FNQGU]

Thanks for the links. You are the eBay king!

Yesterday I fitted up an alloy spacer block and bolted up the radiator fan direct (whilst arguing about the viscous coupling and warranty...) Anyway, massive difference!

On the Kuranda range where a few days ago I hit 103 degrees, I am now only hitting 91 degrees, when really flogging it, and 88 degrees when taking it easy. Temps also drop rapidly as soon as I ease off the gas, and just off the back of the range I found I was sitting on 77 degrees at the Kuranda lights. Tranny temps were also sitting on a nice cool 75 degrees after having climbed to 80 on the way up the range. On a second run up a 10klm long winding road which is a steady climb, in the middle of the day's heat, I managed to top out at 100 degrees celcius, again, dropping off rapidly to idle at 92 degrees (aircon on full blast the whole way too) when I pulled over at the top. Engine temp was down to 71 degrees by the time I cruised back down to the bottom in 2nd gear.

So, I think in my mind I have identified the viscous coupling on the fan as a major element to watch when it comes to managing engine temps, and thus engine bay temps. Yes, most of you probably just said "duh", but it is all part of the learning curve for me. The fan was still spinning and looked like it was doing its job, but obviously wasn't pulling air like it should have been, plus I reckon that the Engine Watchdog was what brought this to my attention in the first place. Look for any signs of viscous fluid leakage and give it a bit of a turn by hand on a regular basis to check resistance. When I pulled my fan out, it was actually covered in a thin film of the stuff that cleaned up pretty easily.

As an addition to this thread topic - I also had a conversation this morning with the Hood Louvre mob in the USA (link above) who have a lot of experience fitting vents to the bonnets of both race cars and particularly Jeep Wranglers and claimed to have had a NASA engineer involved in design and testing. They are adamant that the louvres work wonders on the Jeep's when the engines are working hard at low speeds (when the radiator fan is doing all the work) and high and low pressures are not really part of the equation. I sent them over a couple of photos of the GU Patrol bonnet with Intercooler scoop and they are going to get back to me with some further recommendations. Will update when they do.

[nissannewby]

Can you look at a clutch style engine fan? Either an air or electric style one. You will use more fuel with the fan running constantly not to mention to noise that comes with the fan running constantly.

At what speed was your testing done at? A fan running constant can also cause restriction at higher road speeds in some instances.

[threedogs]

I used a 5 blade fixed steel fan on my chev troopy but I think that dragged 20 hp out of the motor.sounded like a chopper overhead LOL
I then went to a 6 blade uni plastic fan similar to an OE viscous, much quieter than the steel fan
Would easily hold a sheet of paper to the grill for testing purposes, Plus the fan had to be a certain distance from the radiator
and so far into into the shroud for 100% efficiency.

[FNQGU]

Yeah, I probably wasn't too clear before - I fitted up the direct bolt on fan while waiting for a replacement viscous hub that I believe should be supplied under warranty. Just arguing that out now. The extra noise is noticeable, you're right there! Any suggestions on different types of fan would be appreciated. I was concerned that the electric thermo fans simply couldn't pull enough through the radiator to compare. It would be convenient to have a switch to flick them off for deep water crossings though!

Testing wasn't exactly scientific, but I've been repeatedly running up the same hills at roughly the same times of day when it is at its hottest. Yes, there are no doubt a lot of margins for error in that method, but it is a real-world indicator anyway.

[FNQGU]

For those who also might suffer from overheating, I found this excellent little article on Viscous Fan couplings and the fact that at least for Toyota, there is often not sufficient silicon fluid in the hub from factory. This leads to a less than efficient fan and thus overheating sometimes.

http://neuralfibre.com/paul/4wd/tuning-and-understanding-your-toyota-viscous-fan-clutch

It also shows a step-through on how to add fluid to rectify the problem and increase efficiency, plus there is an interesting comment suggesting that vehicle momentum is not what forces air through the radiator, it is the radiator fan, so efficiency here is super important.

I learned something anyway.

[outback]

FNQGU:
Did you ever get anything back from Hood Louvre, (USA)?

As for "nteresting comment suggesting that vehicle momentum is not what forces air through the radiator", I have some doubts on this. At certain speeds yes forward velocity, hence ram effect is minimal, but at higher speeds it may have a significant effect. Possibly though inhibited by the fan, assuming the fan works correctly. A floating, non working fan though will not effect this ram effect so it can work. What that velocity is I can like others but guess.


In my vehicle I had 2l of coolant missing from the radiator. The temp gague sat on mid point so long as I sat on anything above 65- 70km/h Anything under that it hit top range plus = overheating. This would confirm a concept of ram effect. Also suspect Vicious clutch on fan stuffed so not a real working fan.


I was just advised to get a nice big wide scoop and only use half of the scoop with the Intercooler, and the other half to simply pump air through the engine bay and out the bottom. Or to fit a second scoop for the same reason.


As The evil one said rubbish. You need to drag air in via the radiator and out via the engine bay. be that bottom/ and via vents in the bonnet. The air movement from the intercooler causes some airflow disturbance as far as hydralic, non lamina flow goes so adding more via a bonnet stop will cause poor air flow.

In reality the intercooler air should come in, pass the intercooler and be vented by a secondary duct to the outside not dumped into the engine bay. Not seen this yet.

In my opinion and based on airflow the intercooler can cause added issues as much as all the additional things added to the engine bay. Simply poor air flow.

[jet]

Its all about getting hot air out
The deflector under radiator creates low pressure under engine bay when driving and hot air is sucked out the bottom
Damage this or lift vehicle etc all has potential to stuff this up
More openings in top could also upset this fairly sensitive plan.

Elect Fans under IC actually slow air down at higher speed but slow stuff they can help for sure.

With the mix of legal restrictions on scoops and rear facing openings makes it harder to fix.
Despite it being a pain to live with, increasing size of deflector is maybe the simplest upgrade to air flow
You also need to ensure incoming air isnt bypassing radiator.

[outback]

Its all about getting hot air out
The deflector under radiator creates low pressure under engine bay when driving and hot air is sucked out the bottom
Damage this or lift vehicle etc all has potential to stuff this up
More openings in top could also upset this fairly sensitive plan.

Elect Fans under IC actually slow air down at higher speed but slow stuff they can help for sure.

With the mix of legal restrictions on scoops and rear facing openings makes it harder to fix.
Despite it being a pain to live with, increasing size of deflector is maybe the simplest upgrade to air flow
You also need to ensure incoming air isnt bypassing radiator.

As far as the sensitive air flow in the engine bay is concerned its stuffed the moment you add the second battery, air compress or and anything else like these items.

Air flow is sold defined by air pressure here and with these added items some of the bay will not get the required air movement.

As for air flow at what velocity, hence ram effect on the IC does the electronic fan cease to be effective?
At what velocity does the radiator fane and its cooling become part aided by ram effect also?

Even without the electric fan the air flow through the IC will cause pressure problems with the air via the radiator fan at certain speeds,so intact the air flow via the IC can be reduced.

Anyway unless Mr Ni$$an releases his air flow diagrams and flow values it becomes a bit semantic.
As i also said add more gear to that engine bay and Mr Ni$$an's calculation fall out the window.

[FNQGU]

Yes, I agree that the additions of accessories and batteries must change the amount of room in the engine bay available for air to circulate, and there isn't much there to start with. Hood Louvres say that their testing has shown that the vents work at both high and low speeds as the pressure inside the engine bay is generally higher than the pressure at the entrance to the vents (?). Of note - I was not able to get real test data from them on this to prove what they are saying is a fact as opposed to just supporting their sales pitch, but they insisted that the fact many speedway and race-cars successfully run their hood vents, should be proof enough. The High pressure zones on the Patrols seem to be up against the bottom of the windscreen, on the rise in front of the bonnet scoop, and on the front edge of the bonnet.

The addition of hood vents is also mentioned quite a lot on the forums for Nascars, the Jap racers, Camaro's and various other hot-rod type sites, as being one way to allow hot engine bay air to escape, and really, all the talk of high pressure and low pressure zones surely must relate to times when the vehicle is traveling at least say 75kph (at a guess) and when there is most opportunity for air to flow through the radiator without much assistance from the fan (the mentioned ram effect).

For lower speed situations they are saying that the vents are even more effective, as the fan is doing all the work and it simply blows the hot air straight out via the path of least resistance, which for hot air, is up, if there is a vent. The bigger the vent the greater the effectiveness and the greater the drop in engine bay temps, is the advice they give.

On the issue of the vent facing out at 45 degrees - what would be the point other than possibly the legalities, and without having seen the regs, I am not sure it would be sufficient anyway?

Now that I have fixed my issue with the Viscous Coupling and temporarily installed the direct bolt up fan, I don't seem to have the overheating issue when cruising at highway speeds, or even on long up-hill climbs if the speed is still above say 80 or 90. Towing my 2t boat for a good run still sees my temps sit around 100 degrees when at cruise speed, and get up to 106 degrees working hard. I will however go back to a viscous coupling when I get one, and will probably pull it apart and check the silicon fluid levels before installing it too. To me these temps still are higher than I would like them to be, and surely after a prolonged period of time, would start to cause damage to other components?

Yes, an effective Intercooler would add to the pressure (and possibly heat) flowing into the engine bay, but I would hazard a guess that with the vents in place the extra air can escape just as easily. I note that ARE state that fans beneath the Intercooler only really work at low-speeds for the same reasons, and are a hindrance to airflow at higher speeds.

Hood Louvres told me that large centrally located vents are the most effective for all round use. On race cars, large vents situated on the bonnet just behind the radiator fan is a good place as it is the place of lowest pressure at speed. On 4wdrives doing a lot of low to medium speed hard work, a large lengthwise vent over the turbo and dump pipe is highly recommended along with a matching one for aesthetics on the opposite side.

This whole area of aerodynamics and thermal dynamics is a minefield. Change one thing and it affects another thing...

So, I suppose that if you have covered all the other options to reduce engine bay heat (exhaust wraps, turbo blankets, ceramic coatings, thermostats, radiators, viscous couplings, deflectors, foam seal on the front of the radiator, etc. etc.), and are still concerned about it, then these types of vents might be worth a look at (legalities not considered). The big thing for most people (again, besides the legalities) is probably the aesthetics of the whole thing, and whether they want to 'ruin' the OEM look of their vehicle.

Another option for those who want to stay legal, would be a custom bonnet such as this one designed for an 80 series. The manufacturer makes them from fibreglass and does one for the GU which looks the same however can have the bonnet scoop added. At $880.00 and still in need of painting, it isn't cheap, but might also work.
http://i935.photobucket.com/albums/ad197/BenKDJ/Custom%20Bonnet_zpsqyvk74np.jpg (http://s935.photobucket.com/user/BenKDJ/media/Custom%20Bonnet_zpsqyvk74np.jpg.html)

[threedogs]

IMO if your temps are up It can only be radiator not big enough, eg I used a V8 holden one in my 350 chev 4x4
or not enough water flow, again I updated to a John bennet water pump. just saying
and I also changed the radiator neck to the larger holden type

you could duct cold air in via the bottom using some pvc ducted to the right area

[FNQGU]

John, the radiators that are installed by Brunswick Diesel are as big as i have ever seen fitted into a Patrol. I'm not sure it is the radiator itself in my case. Airflow? That is another question...

[AB]

My brother has been having severe overheating problems with his gu ute 6.5 chev.

The radiator was a custom made ally one and just spent a small fortune at a local radiator place on a new custom built brass one.

The bloke mentioned about a lot of radiators have the fins too closely together.

Long story short he did a run up radiator test hill on a hot 35 degree day with air con blaring and driving it hard and it did not push past halfway on his gauge.

It did cost him some $$$ but problem solved and some!!!

[threedogs]

Mate I went to everyone in Melb with this prob, jet coating block huggers inside and out.
I spent a fortune on it, too much then enter John Bennet, He designed the cooling systems for the V8 super cars.
I once spent 4 hrs just talking cooling. Try to google him for a contact as no one knows more than him.
Personally I dont think radiant heat is the problem have you tried additives like wetter water?
Your fan should give you sufficient air flow what are 12v fans pushing/pulling 20,000 fpm thats plenty
I think AB has the solution
even back hoe coolant was mentioned at one stage

[threedogs]

Mate I went to everyone in Melb with this prob, jet coating block huggers inside and out.
I spent a fortune on it, too much then enter John Bennet, He designed the cooling systems for the V8 super cars.
I once spent 4 hrs just talking cooling. Try to google him for a contact as no one knows more than him.
Personally I dont think radiant heat is the problem have you tried additives like wetter water?

http://www.ebay.com.au/itm/RACE-DRAG-RALLY-DRIFT-CAR-COOLANT-CONCENTRATE-GLYCOL-FREE-WATER-WETTING-AGENT-/131404673689?pt=LH_DefaultDomain_15&hash=item1e98543299


http://www.ebay.com.au/itm/MARINE-WHITE-ABS-PLASTIC-LOUVERED-SLOTTED-VENT-FOR-BOAT-FIVE-OCEANS-/281319656702?pt=Boat_Parts_Accessories_Gear&hash=item417ff54cfe

[AB]

I'm really interested to hear from anyone who has tried that Evans waterless coolant.

That ship is expensive but would love to get any feedback?

[BigRAWesty]

I'm really interested to hear from anyone who has tried that Evans waterless coolant. That ship is expensive but would love to get any feedback?

Well don't be shy. Jump in and try...

[4bye4]

I'm really interested to hear from anyone who has tried that Evans waterless coolant.

That ship is expensive but would love to get any feedback?

I have read about it but would worry that if you did stake a radiator or something in the bush and lost it, can you go back to water to get out of trouble.

[threedogs]

I'm really interested to hear from anyone who has tried that Evans waterless coolant.

That ship is expensive but would love to get any feedback?

Just saw the ad on SBS and was going to post but you beat me to it.
there are three different types, My BIL used backhoe coolant in his 302 powered 75s ute.
not sure how it went as we all went down the John Bennet road and all was cured
http://www.evanscoolants.com/evans_waterless_engine_coolants_faqs.html

just doing some searching and found most prefer to use Redline water wetter and water
to keep temps down, as Evans raises your temps slightly, including oil temps

[Winnie]

I'm really interested to hear from anyone who has tried that Evans waterless coolant.

That ship is expensive but would love to get any feedback?

I thought it was just to prevent corrosion, not improve cooling efficiency.

[threedogs]

It would lift your boiling point ,plus give you Anti freeze.
as well as what you said anti corrosion, more a 3 in 1

[FNQGU]

So, just for interests sake, I pulled the thermo coupling off my transmission pan, with the idea of attaching it in different places around the engine bay to try and gauge just how hot the engine bay gets compared to the the second thermo coupling which is mounted on the thermostat housing. The temps are being monitored from the cab via the Engine Watchdog.

So far, the bracket holding the start battery down regularly gets into the 70 degrees celsius range and seems to be generally around ten degrees less than the thermostat housing under the varying driving conditions and temps.

More to follow...

[Crankshaft]

I did a bit of a test when I raised the back of the bonnet on some spacers. It is simple to do
Just tape some bits of wool about 4 inches (10cm for those younger than 40) to the bonnet near the gap.
On My Mk the air flow was down not up!
It follows that the air was going out underneath as happens with formule 1 fairing.
It also follows that means less air through the radiator. as the evil twin suggests.
I fitted twin falcon electric fans with little improvement.
Ended up fitting a 3 core radiator and that has made it better but it is still not happy in LowLow in the bush on a hot day.

[FNQGU]

It is the low speed stuff where mine gets hot as well. I reckon the lifting of the bonnet at the rear would work at low speed, but not at higher speeds due to the well documented pressure differences at the base of the windscreen.

Venting of the bonnet seems to be an option for constant low-speed heat issues, but I'll try and get a semi-decent understanding of my engine bay temps before making any radical decision on bonnet venting though. Bonnet venting at high speed is also very effective if the vents are placed correctly in the low pressure zones.

I currently have the thermocouple attached to the front of the Top Mount Intercooler, directly above the engine. Temps here also similarly rise into the mid-70's at low speeds or idle, but drop a lot faster when on the move. When driving, the temps typically sit anywhere from 15 - 20C lower than the top of the Thermostat, and probably 5 to 10 degrees lower than the battery area. eg. if my Thermostat is sitting on a constant 80C, then the front mount of the intercooler can be anywhere from 60-65C. I assume this is due to the amount of air flowing through it when moving.

Next I will move the thermocouple over to the top of the air-box, or perhaps behind the radiator overflow reservoir on the passengers side.

[threedogs]

I find it hard to believe only one patrol here is suffering from "HEAT BLOCK" after all the problems I had with my 350 chev troopy in a triangle shaped engine bay, Rob Kay from ARB Northern even made a perspex bonnet to check air flow.
To the best of my knowledge I think your problem is your radiator.
all the others with the 6.5 chev have had teething problems but nothing like you are having.
if fitting the vents on the bonnet dont help Id be looking seriously at a new radiator fan set up.
Even the fan can make a huge difference , I fitted a steel 5 blade,, noisey as but cooled down the motor
6 blade plastic was OK and the OE clutch fan worked well also, then you need to have the shroud properly made with the fan
in the right position in with the shroud a little out and youll have problems.
Trust me Ive spent thousands of $$$$ and many different set ups getting it right over many years
it was a work in progress

[gramgramfirey]

Overheating is also caused by cavitation of coolant in the engine. If the coolant can`t contact the water gallery walls then it can`t cool the engine. A friend of mine and gq owner was having this problem. One of the waterless cooling gurus told him to use their cleaner to clean the inside of his engine and then use their glycol product and it worked a treat. The inside of the cooling galleries get blocked over time a bit like cholesterol in your arteries.
Get rid of it and the heat transfer between fluid and engine gallery walls is restored.
Liquid intelligence was the company. They sell kits on Ebay for around $200ish.
As said my friends GQ with 2.8td, not renown for it`s cooling efficiency seems great now.