GU A/C Fan?

[TuffTD42]

Hi guys, Just a couple of questions regarding GU TD42. Just bought one for the missus. It gets hot towing (Mainly up hill) as most TD42's do. But I reckon it gets hot a lot easier than my GQ. It actually boiled, My Gq doesn't. What I noticed with the GU which to me seems a bit arse about is the A/C Fan sucks air back out of the engine bay & not from outside the front of the vehicle. I think that this is the correct operation as the shroud has cut outs to allow this. I would of thought it would have been more efficient to suck from out side the front not back out from the engine bay? I notice aswell that the engine fan missus out cooling that part of the radiator due to this set up. I reckon It would be better of removing the divider, covering up the cut out in the shroud & reversing the A/C fan. hope this makes sense. cheers Jono.

[the evil twin]

There is no way it should suck out of the engine bay...

It should be set up as a pusher and draw air from the grille and "blow" it thru the A/C and radiator

You might want to double check your fan rotation and DO NOT cover those bypass cutouts, they are there for a reason

[TuffTD42]

I'm with you evil. But if you look at the setup it make sense that it dose what it is doing. Evil, Why are the cut outs there in the shroud if not to serve this purpose? The way I see it there only purpose is to allow that A/C fan to suck the air back out of the engine bay. There is a divider between the shroud & the radiator so the engine fan can't suck through that part of the radiator. My opinion is that, this is the proper operation but is silly & what I think is contributing to the over heating/running hot in the GU TD42's. I would like to hear more theories on this or facts. Also has any one reversed the polarity on the fan or reversed the blade & covered up the cut out. Also the divider would have to be cut out.

[nissannewby]

Sounds like the radiator is either internally or externally blocked. Rip it out and give the cooling system a service. If its blocked externally it will be quite noticeable when cleaning it out.

[TuffTD42]

I drove it in 50deg heat with out trailer & it got hot. had to do 40klm/h at one stage to keep it cool. I have fitted a brand new viscous hub. After market (dayco) not convinced this is a great brand but I got it for free. I pulled the radiator. reversed flushed it & the engine. blew all the shit out of the fins including the A/C Condenser. checked thermostat operation. Refilled with Nulon coolant at approx 33% mix. . The missus towed me mates paj, about a 50klm trip. It sat just under half way most of the way. The highest it got was just under 2/3rds on a long hill. It was evening & about 24deg. We then towed a GQ I bought & it ran hot on every hill boiling on one. had to pull over & let it cool down. There is no visual signs of head gasket or cracked head probs. Not towing it sits just under half & climbs to just over on long hill climbs. Pissing me off is an under statement, seeing it's purpose is to do all the towing. Horse float & car trailer duties.

[gaddy]

Im with newby mine did the same i cleaned it externaly and flushed now good as gold the amount of mud from between the fins was huge

Gaddy

[TuffTD42]

Im with newby mine did the same i cleaned it externaly and flushed now good as gold the amount of mud from between the fins was huge

Gaddy

If you read my last post? I have already done all this. seems to have helped not towing, but no difference towing.

[TuffTD42]

I Know a lot of the tricks to get TD42's to run cooler. I am in the process of modifying a thermostat to see if that helps any. What I'm more interested in, is why the shroud has the cut outs? Why the A/C fan sucks from engine bay rather than pushing into it. Has anyone actually done what I'm thinking of doing. Reversing the A/C Fan, covering the cut outs up,Getting rid of the divider so the eng fan actually sucks through the whole radiator.

[gaddy]

Sorry tuff i was typing my response when you posted that bit, work interupted me
Gaddy

[TuffTD42]

Sorry tuff i was typing my response when you posted that bit, work interupted me
Gaddy

No worries mate.

[the evil twin]

I'm with you evil. But if you look at the setup it make sense that it dose what it is doing. Evil, Why are the cut outs there in the shroud if not to serve this purpose? The way I see it there only purpose is to allow that A/C fan to suck the air back out of the engine bay. There is a divider between the shroud & the radiator so the engine fan can't suck through that part of the radiator. My opinion is that, this is the proper operation but is silly & what I think is contributing to the over heating/running hot in the GU TD42's. I would like to hear more theories on this or facts. Also has any one reversed the polarity on the fan or reversed the blade & covered up the cut out. Also the divider would have to be cut out.

Nah mate... the proper operation is for the fan to be a pusher.
Either that or every vehicle i have owned is back the front. If the fan is a puller how can it draw air when there is a 100 KPH 'wind" blowing in it's face as you drive.

I don't know how yours ended up the wrong way round to how IMHO it should be but if it is indeed correct and should be a puller then I will be a tad gobsmacked

The A/C condensor fan should come on with engine running and A/C selected, draw cooler air from the grille and push it thru the Condensor then the Rad then expell it thru the shroud openings.

All the GU Patrols are set up that way AFAIK (but i haven't seen every series) with similar shrouding. The airflows are fairly complex and rely on the rubbers all being in place along the chassis rails inboard of the guards and below the rad etc etc. to keep the differential pressure relationships kosher

You can clean and backflush to your hearts content but if the Rad is clogged then rodding it is the only way.

Without telling you to suck eggs you weren't towing in 5th/overdrive were you?

[TuffTD42]

Nah mate... the proper operation is for the fan to be a pusher.
Either that or every vehicle i have owned is back the front. If the fan is a puller how can it draw air when there is a 100 KPH 'wind" blowing in it's face as you drive.

I don't know how yours ended up the wrong way round to how IMHO it should be but if it is indeed correct and should be a puller then I will be a tad gobsmacked

The A/C condensor fan should come on with engine running and A/C selected, draw cooler air from the grille and push it thru the Condensor then the Rad then expell it thru the shroud openings.

All the GU Patrols are set up that way AFAIK (but i haven't seen every series) with similar shrouding. The airflows are fairly complex and rely on the rubbers all being in place along the chassis rails inboard of the guards and below the rad etc etc. to keep the differential pressure relationships kosher

You can clean and backflush to your hearts content but if the Rad is clogged then rodding it is the only way.

Without telling you to suck eggs you weren't towing in 5th/overdrive were you?

Nah, I never tow in 5th. I'm guna have to check out some other GU's A/C Fans. but why the divider between shroud & radiator so the eng fan can't suck air through that part of the radiator. I agree it should be a pusher, but looking at the big picture it seems that it's set up as a puller, Which is just stupid. Anyhow if I haven't shot it before hand I'm guna try the mods I mentioned. Wouldn't have thought the radiator was blocked by the amount of water that flushed through it. I fill it up then remove the bungs & see how quick the water flows out. I do this twice radiator upside down the 2nd time.

[the evil twin]

Uuuummm, you have physically checked the fan rotation like I suggested in the 2nd post or are you just assuming its a puller....?

You can sort of treat the GU cooling system as "split" IE it has an engine driven fan and an electrical fan with a common radiator.

The elec fan is there for two reasons.
It will come on to boost air flow and therefore cooling when the A/C is on regardless of coolant temp. This cct is via the A/C control relay
It will come on when the coolant temp exceeds a set temp of approx 90 deg C in the lower tank even with the A/C off to assist the engine fan. This cct is via the high temp switch
(EC242 for TD42 variants of the manual refers)
As can be clearly seen in the manual the fan blades should be rotating clockwise (viewed looking towards the rear of the vehicle) pushing air from the front of the vehicle thru the rad etc

The divider is there because the engine fan will look like an obstruction to the airflow from the A/C elec fan at low speed low RPM IE idling at the lights or whatever.
If the ports are closed and the divider removed then all the air has to flow past the engine fan. If that is the case then the Elec fan serves no purpose.

This all means they can save some horsepower and fuel and reduce emmissions by not having to drive a humungous engine fan

[TuffTD42]

Uuuummm, you have physically checked the fan rotation like I suggested in the 2nd post or are you just assuming its a puller....?

You can sort of treat the GU cooling system as "split" IE it has an engine driven fan and an electrical fan with a common radiator.

The elec fan is there for two reasons.
It will come on to boost air flow and therefore cooling when the A/C is on regardless of coolant temp. This cct is via the A/C control relay
It will come on when the coolant temp exceeds a set temp of approx 90 deg C in the lower tank even with the A/C off to assist the engine fan. This cct is via the high temp switch
(EC242 for TD42 variants of the manual refers)
As can be clearly seen in the manual the fan blades should be rotating clockwise (viewed looking towards the rear of the vehicle) pushing air from the front of the vehicle thru the rad etc

The divider is there because the engine fan will look like an obstruction to the airflow from the A/C elec fan at low speed low RPM IE idling at the lights or whatever.
If the ports are closed and the divider removed then all the air has to flow past the engine fan. If that is the case then the Elec fan serves no purpose.

This all means they can save some horsepower and fuel and reduce emissions by not having to drive a humungous engine fan

I haven't checked the rotation,I'll check that out in the morning. When it ran hot on the first trip, I was under the hood & could feel the A/C fan pushing shit loads of air out towards me, not pushing it in thru the radiator. I know about the switch's in the bottom of the radiator. As for the obstruction, Personally I think it would be better off letting the eng fan pull air thru the whole radiator. Thanks for the info. I'll see if I can rectify the A/C fan & see what difference it makes.
cheers Jono.

[nissannewby]

All the earlier GU's (wide radiator) had those shrouds. The later GU's do not (tall radiator). Does it still get hot without the air con on? As evil twin has mentioned the A/c thermo should only come on when the a/c is turned on. It will hard to tell if the core is blocked just by using a hose and dropping drain bungs. The fluid will always take the easiest route and back flushing with a hose with cold water doesnt have the pressure that your cooling system has under working conditions.

[TuffTD42]

All the earlier GU's (wide radiator) had those shrouds. The later GU's do not (tall radiator). Does it still get hot without the air con on? As evil twin has mentioned the A/c thermo should only come on when the a/c is turned on. It will hard to tell if the core is blocked just by using a hose and dropping drain bungs. The fluid will always take the easiest route and back flushing with a hose with cold water doesnt have the pressure that your cooling system has under working conditions.

It still gets hot regardless if the A/C is on or not. Even tried the heater trick with no success. To my understanding is the A/C fan will come on regardless if the A/C is on or not, hence the 2 sensors at the bottom of the radiator. 1 turns the A/C off if the engine reach's a certain temp & the other turns the A/C fan on like wise.

[the evil twin]

If the heater doesn't help then it is getting seriously hot alright... I still reckon you need to rod the rad, even if only to rule that out as an issue

[TuffTD42]

If the heater doesn't help then it is getting seriously hot alright... I still reckon you need to rod the rad, even if only to rule that out as an issue

Yea I'll look at that, might throw a new one in. process of elimination now.