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Hey guys,

After finding and fixing the misfire in my GTR, I've had yet another set back. Its now got a cooling system problem.

After a drive a few weeks ago it was bubbling (boiling) in the radiator and/or overflow bottle. I let it idle for five minute with the bonnet up (fan on) and it stopped bubbling. The needle on the temp gauge didn't move at all really. I thought maybe I just hadn't given it enough time to cool down after boosting.

I hadn't really driven it much lately because of the misfire and no insurance, but I've got those two sorted out now and it will be getting a lot more use.

It was bubbling fairly loudly yesterday after a drive, and I had cruised downhill in 5th gear for 3kms or so before I stopped, after a mild drive back on the highway so it should have cooled ok I would think. The gauge had risen to 3/4 after fanging, maybe just over.

Also, leaked coolant from somewhere, which I hadn't noticed before. Maybe 200ml or so. It was late and I didn't have time to check it out properly.

Now, my question for those of you who are kind enough to help me out:

What should I be checking, replacing or looking at to remedy this situation?

My list so far includes:

1. Coolant flush and repalce. It hasn't been changed from Japan yet (only a few 100kms). Should I do this myself, or take radiator to a radiator place to clean? What about engine side?

2. Check thermostat. Whats the likelihood of this being jammed or stuffed or something? Someone suggested just don't run a thermostat.

3. Obviously, check for leaks. Any points I should look into specifically?

Thanks in advance for your help guys.

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Ok im not fluent with Skylines but cars in general i know quite a bit so the things you should be doing first...

(Try pinpoint the leak)

***Check all your hoses and tighten or renew accordingly.

***Flush radiator.

-Park the car on a slight hill (driveway) so the nose is higher.

-Disconnect top and bottom hoses.

-Run the garden hose through the bottom radiator hose and turn it on. Now run the car on idle.

-This should flush the system of bad water.

-Replace all hoses and fill radiator with coolant.

-With the cap off run the car at idle again. The water level should drop slightly; top up with water.

-Let the car run/idle for approx 15/20 min. Any air bubbles should rise and come out the radiator cap.(Reason you park on a hill)...(Not sure if the skylines have bleeder. If so it'll be ontop/near the thermostat)

-When you are satisfied there are no more air bubbles close it up.

-Drive the car and recheck water levels.

If this has not remidied the situation even if u've pinpointed the leaky hose and changed then you would most likely need to change ur water pump. I suggest you take it to a mechanic for that job.

---------

In regards to the thermostat being 'stcuk open' no this wont overheat ur car. The thermostat opens up as it reaches its desired temp hence letting fluid pass through the radiator. When they become lax they simply stay open. The resulting effect is a car that wont warm up as quick in the mornings...

Thanks guys.

Scooby, it doesn't have a misfire anymore. It did have, but that was injector related and has been fixed now. Also, I've checked the water for oil and found no sign, although it was a bit dirty. The oil is only a few 100kms old and I can't see any sign of water in it either.

So to flush the engine of the old fluid I disconnect the rad hoses and connect the garden hose to the bottom rad hose going into the engine? And do the same to the radiator?

Should I used some kind of engine flush chemical treatment?

Could it be related to bad ignition timing or something like that?

One air bleed point is on the heater hose on the firewall... have a look and you will see it... not sure if the GTR's have one on the plenum as the GTSt's do...

Your problem sounds strange that the temp drops when you stop fanging it... I had bad cooling issues with mine and at first it was a blocked radiatior, then it was a leaky core and end tanks... In the end I just had the whole radiator replaced as it was not servicable... cost me just over 700 for a brand new radiator and all associated labour & fluids etc.. But once it got hot - it woulnd't cool down... Your issue probably different to mine.

I'd get yours checked out by a proper radiator joint, but try all these other options first... Don't take it to a performance place to get them to sort it out.. you will end up paying a lot more... trust me I know..

Are you running the factory fan or a thermo?

The Japs don't take good care of their cars, and don't treat the cooling system with coolant. I'm therefore guessing that the water pump is not healthy.

Ok, sounds like I should do the basic checklist and if its still not right I'll get it checked out.

Am I on the right track re the engine flush procedure?

How do I check a radiator cap? Apart from visual?

Yes it is factory fan I believe. Also, radiator cap is a Cusco high pressure unit, if that has any significance.

:blink: <_< mm with ur high pressure radiator cap it might be too high which may allow the pressure in the system gettin too high blowin something so ur leak u noticed might be ur best beat but try puttin ur old radiator cap back on see what difference it makes.

If it doesnt clean around were u found the coolant or were coolant may get out, go for a drive pull over after ur eng temps gettin weird and check for any noticable leaks eg hoses,head, water pump and the radiator itself.

As said b4 ur thermo wouldnt be the worry but if u want pull the guts out and put it back in just wont warm the eng as quick when its cold to eliminate it.

Thanks guys.

Scooby, it doesn't have a misfire anymore... Could it be related to bad ignition timing or something like that?

Glad to se you found the misfire - so thankfully not likely to be a head gasket. If it was timing you'd prob have heard it ping by now, you need a fair bit to make it overheat that much.

Check the thermostat, they have been known to fail but it's not common. The leak is interesting, def pursue that. When they purge water they suck air back in at the same place but again it's got to be quite a bit to make it behave badly. Over time however...

Water pump yes is a possibility but then it happened suddenly which is interesting. Or at least you noticed suddenly which is a different thing, just means it got to the point that there were av signs. Check the water pump housing for leaks, if it's got one and sucking air it will cause cavitation= no flow.

Had an interesting experience with a Honda once, drove it 1800km in 40 deg heat no problem. Return trip 300 km down the road and suddenly got huge temp, tried everything like flushing rad etc but turned out to be the fins. Fins were like powder and I'd never seen anything like it, presume with that metalurgical make up ie crystaline make up were useless at anything other than er...being powder.

If you go to a rad shop they can pressurise the system and that might help in identifying the leak, just don't let them sell you anything until you know what the problem is.

Cheers

  • 2 weeks later...

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