Coolant from Radiator going to Reservoir, but not returning to radiator on cool down.

Hello,

I refer to my intro. of approx. 08/02/'11, in the auto elec. area.

Thank's for your advice, it helped.

For nearly two years now my 1989 GQ LWB Patrol, ("Neville"), has been suffering the above.

He has been to 4 different mechanic's, 2 4X4 specialist mechanic's and 2 Radiator specialist's.

Most of these people I know and trust, (They know their stuff).

So far none of these people have been able solve the problem.

If we go for a decent drive of length, particularly a hot day, the coolant goes to the reservoir but on checking the next day, does not return to the radiator. we are not losing any coolant, unless I don't get to it in time.

This promblem does not show up on the Temp. Gauge and the mechanic's state that the gauge is fine.

I drain the reservoir back to max. level and return it back to the radiator, although it takes me at least 2 days to do so because usually the radiator at first appears full just driving around my town.

All of the above people have pressure tested the radiator, hoses, head gasket, reservoir etc., and I usually leave him with them for a few days so they can heat everything up, and watch what happens.

We have replaced Hoses, (except Heater Hoses, I think), Themostat, numerous radiator caps of differing pressures, and numerous other things, but so far to no result.

I have suspected the old radiator, but the radiator people cannot see this as the problem, although they cannot say for sure.

There is no oil in the coolant and no coolant in the oil.

We have spent a lot of money on this problem and it's driving us nuts.

There is a leak, or whatever , in the system and we just can't find it.

During the course of these tests we have spent quite a bit of money getting Neville back to near mint condition, new suspension, steering, rear window seals, electronic ignition etc., etc.

We would really, really appreciate any idea's or advice as to where next.

Regards,

norm aj.

"If we go for a decent drive of length, particularly a hot day, the coolant goes to the reservoir but on checking the next day, does not return to the radiator. we are not losing any coolant, unless I don't get to it in time."
How full does the reservoir get when this happens? Is it just to the HOT line or close to full? When the engine is cold and you remove the radiator cap, is there any pressure behind it?


"I drain the reservoir back to max. level and return it back to the radiator, although it takes me at least 2 days to do so because usually the radiator at first appears full just driving around my town."
This sounds like there may be exhaust gas getting into the cooling system and creating an air lock in the system. Next time this happens and the radiator appears full try bleeding the cooling system. Run the engine at around 1200rpm with the radiator cap off and the heater on until the thermostat opens (coolant will start to flow through the system and radiator will suddenly warm up). If there is any air or exhaust gas in the system this will bleed it out and the coolant level will drop.

Given that the problem only occurs with the engine running it is likely that any air lock would actually be exhaust gas not air, and the problem is going to be finding where the leak is, it will only be a tiny leak.

Tony

Water goin into reservior but not returning
When its running hot can you hear a bubble effect in the reservior ???
When the radiators are blocked it will go into reservior and be that hot the hot water expels in the colder water to creat bubbles (like boiling water if u like)
Id be getting your radiator rodded out
Pressure test dont think that will tell how blocked the rad is

this may be frowned upon but IMO the best way to diagnose this is to get a bottle of bars radiator leak (the little chicken poo pellet things). Put that through your radiator system and drive the car around for 20 minutes when you do it then again for a week. Check in a weeks time if the problem is still there? It can take a week for it to fully seal. If the problem goes away then you have a cracked head between two valve seals or a leaky head gasket (my bet is a cracked head though)...

If the problem remains then it could be your radiator cap...

You could replace that first though just to rule it out... As long as you have an original top tank use an original cap... Measure the offset and make sure it really is seating properply... I once had a cap that missed out on seating by 1 mm and you couldnt tell but the car had the same symptoms..

Had a problem very similar to this a few times over the years. As the engine cools down the water contracts creating a pressure drop which then supposedly sucks the coolant back out of the overflow tank.
I f there is a minute leak in the return hose or fitting the suction required to return the coolant will draw air in instead of coolant. This will of course maintain the high level in the
overflow tank. It does not always show as you would expect. There is no pressure in this hose so the coolant flows freely into the overflow tank. If the pin hole was on the top as an example
a leak would not show and it would freely draw air in from the top.
Withdraw the hose from the overflow bottle, take the radiator cap off. Block the outlet in the radiator neck with one finger, suck on the end of the overflow hose, without drinking too much coolant. The hose and fittings should hold vacuum without falling.
Cheap fix when it works, and often overlooked.
Phil.

Phil I was thinking same,about hose with hole, but like Tonys' solve.

First thing I would do is replace the hose from the radiator to the overflow tank. These can age over time and the ends enlarge and no longer seal. Failing that - you have nothing to lose - put a tube of Silver Seal into the radiator. I have had to use this once when I cracked a radiator (in a Toyota of course) just out of Birdsville. I was amazed at how quickly it sealed everything up and it got me back home with no problems and no bad after effects to the engine. I swear by it now and always carry a tube (to help out broken down Toyotas and Mitsubishis - cause thats the kind of guy I am !!!).

Me and my dad had the same problem with both of are patrols and we found out it was the radiator cap, at the time we were using ones that looked like the original but they had a rubber center, when replaced with one with a metal center it sorted out the whole problem.

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Originally Posted by BillsGU

First thing I would do is replace the hose from the radiator to the overflow tank. These can age over time and the ends enlarge and no longer seal. Failing that - you have nothing to lose - put a tube of Silver Seal into the radiator. I have had to use this once when I cracked a radiator (in a Toyota of course) just out of Birdsville. I was amazed at how quickly it sealed everything up and it got me back home with no problems and no bad after effects to the engine. I swear by it now and always carry a tube (to help out broken down Toyotas and Mitsubishis - cause thats the kind of guy I am !!!).

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haha Bill, I know what you mean, couple of my mates have Toyotas and I'm for ever spending time helping them out, broken CV's, clutch you name it lol and guess who has to tow them home..??? The Nissan of course!

Are any of the "numerous caps" you have tried been genuine Nissan?... I have heard of more than a few issues that have disappeared when a genuine cap was used like CraigGardiner dude mentioned.

It may be worth one more shot at a Radiator Cap, replace the hose from overflow to radiator (if you haven't already) and especially check the hose that goes from the overflow bottle cap down into the fluid. That hose is also a source of air getting into system. I put a small cable tie on one once for a similar issue.

The actual "suction" pressure to draw the fluid back is quite low so any air in the system is a PIA and causes any amount of weird symptoms so the final step would be to "bleed the system as per Tony's post and also if the engine is cold then drop the resorvoir level down to min/cold not max/hot.

If it still does it after that and considering the previous tests you have done then it pretty much has to be a hairline crack somewhere letting gas pressurise the system. They can do analysis checks on teh coolant to see if that is the case.

Hope you get on top of the problem with a cheap solution.

What make you so sure you don't have coolant in your oil. Have you had it tested?

Radiator pressure testing can sometimes lead you astray because most pressure testers do not test the sealing on the top of the filler neck or the small tube soldered into the neck for the overflow tube. The best way to pressure test is to use a new radiator cap and remove the lower seal that seals in the bottom of the filler neck, connect a pressure tester to the end of the overflow tube. You can use a push bike pump and old push bike tube valve stem to connect up to pressure the system to about 13psi. This type of test will test the full system including the overflow hose.

If you have checked for leaks in the overflow hose and replaced the radiator cap and it is still pushing water into the recovery bottle it is likely to be a head gasket or cracked head. To test you can use the radiator cap that was modified for the pressure test. You should also disconnect the fan belt that drives the water pump. Then put the overflow hose into a clear bottle to see if you have bubbles. Rev the engine and watch, if you have constant bubbles then you have combustion gas leaking into the cooling system. A very slight leak might not show unless you go for a test drive, make sure that the fan belt is refitted and you can use a long hose and put the bottle in the cab, but be carefull because it may get hot and burn you if the hose comes out of the bottle. The bubbles may show up only under heavy acceleration if it is a slight leak.

I like the idea of faulty rad cap.

Is the radiator gen or aftermarket, maybe something isn't to spec in size and not sealing correctly.

You noted in post 2 no oil or exhaust in water, so I assume if this is ok then,going out on a limb.
why dont you have the entire system vacume tested cold and see if ya can find a leak.
this will require a adaptor for a vac pump to connect to coolant system.

You have something closed when hot, but open cold.
so a vac test might give a result.
If the system cant hold a vacume, then you have a leak for sure.
A spray bottle or hose squirted may assist in finding said leak, listing for sucking noise with water should assist in detection.

Yeah as robo said could be an air leak as air is easier to suck than water so check all your hose clamps etc as they may not leak fluid but have a slight vacuum/air leak mine is doing the same so have to go down this same path of diagnosis.

Quote:

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Originally Posted by squash

What make you so sure you don't have coolant in your oil. Have you had it tested?

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Shouldn't need it tested. Just drain the oil and you will see it. The two don't mix...
You obviously run the car without the cap on to see if any bubbles appear when it gets hot...I would change the hose to the reservoir and make sure all the clamps are in good nick and tight.
If it were me, I would change the said hose, tighten all clamps, and get the entire system pressure tested to see if it hold pressure. Atleast then you would have some sort of starting point.