HDJ81 Cooling Help Please!

[PontiCad]

Here's the situation.

If I drive for a long distance (> 300Kms) at speeds above 90Km/h, the temp gauge stays planted level (normal operating). Everything looks fine, whether I am going 90 or 120, the temp never budges. This is at a relatively high elevation, with long grades etc.

The problems start when I come into a town and have to stop. I pull over (usually going 50-60km/h for a couple minutes before), let the truck idle for 5-10 minutes to cool down the turbo. Again, temp gauge stays planted.

BUT

while it is idling, I peer under the hood to see the coolant resevoir full and coolant dumping into my battery tray! The last time this happened I shut her down, gave it 5 minutes then drove away. Almost instantly, once restarting and pulling out, the temp JUMPS up to just under the high mark, and won't budge until i let off the throttle. At this point I pulled over again, let it cool, cracked the rad cap and topped it off. Start it up again, leave town and the temp gauge stays level for another 600Kms!

It does this the last 2 times I have done my 800km drive home. The last time was the worst, in that the temps just shot up.

What would cause the temp to skyrocket after stopping? When i drive through a town without stopping, the temp doesn't budge (until after you start driving).

It seems as if it is dumping coolant everytime i stop after highway driving now, but it may be because the resevoir was already full.

What i don't understand is why the coolant is spewing out but the temp gauge won't budge.

I have:

-checked the cold tension on the clutch fan (hard to test, seems ok).
-checked the tension on the drive belts
-looked for obstructions in the rad.
-checked the flow from the resevoir for blockages. none.

Theory:

Sticky thermostat??? Or what? Help!

p.s. head gasket?

EDIT: sounds very similar to the radcap issue here: http://forum.ih8mud.com/80-series-te...-overheat.html

Ordered a new tstat and gasket and cap for the truck anyways for spares. Crossing my fingers that the cap is crap. i will test when im at the dealership.

[Tapage]

Start with cheap thinks .. rad cap, testing properly the fan clutch at cold start and normal operative temp.

I don't think if will be a head gasket related .. but you can do the bottle test anycase .. just to be sure.

[canucksafari]

If it is the head gasket, it would be pushing air into your cooling jackets on the head all the time. I wonder if the thermostat is shot. If it closes to early when shutting down it will overheat and force coolant into the overflow tank. Like the rad cap, its a cheap place to start.

[PontiCad]

I checked it out a bit more today while i wait for the parts to come in.

rad cap still has spring tension in return and release circuits. I tried blowing down the overflow line with the cap on, could not get any air past the return valve (the water level was down to the cores) so that may be a hint. But there was less coolant in the resevoir line than last night when it was hot, so somehow that had to have gone back into the rad...Judging by the light tension in the return spring i should have been able to open it with my little lungs...So it may be the cap, but i will still test it at the dealership tomorrow.

I topped off the coolant in the rad, and with the cap off i started her up and set the throttle to ~1500 rpm. Coolant was steadily flowing out of the rad. Once the temp needle started to get to the middle, the bubbles started coming out of the rad, and once coolant was warm it turned into a bunch of tiny bubbles coming out of the rad. I'm assuming this was when the thermostat opened up, as the coolant level dropped down a bit. I don't want to assume that this is a head gasket issue, as i haven't given enough time to let it warm up. Matter of fact after i send this I will go out and try a complete purge and see if the bubbles go away, cross your fingers...

Questions:
-Should i be seeing foam collecting at the top of the rad? I know the air is purging but the foam is new to me, all my previous experience with filling rads has just been bubbles.

-What should I expect to see when the thermostat kicks in? should the coolant level decrease dramatically and stay down?

I know I didn't purge it completely. That was after about 5 minutes at ~1500 rpm and warm.

Just to add, i don't see any obvious leaks either.

Shouldn't it be obvious when the thermostat kicks in? It seemed like the coolant would dip, then come back up intermittently. I suppose this could just be the air working itself out...

I guess if the cap checks out okay, then i'll be swapping the thermostat out tomorrow. I have now completely screwed up the mix of coolant to water, so i will get some more red stuff and drain the old crap tomorrow as well.

Of course this stuff always happens when you're supposed to be doing things like pack your house up and drive 800km home...

[roscoFJ73]

I would change the cap and be sure.
There is no way you could open the spring with your lungs even if the spring was weak.
When the thermostat opens ,you can feel the warm water entering through the radiator hose,its quite sudden.
Takes about 5-6 minutes from cold
I had some of that foaming and after a new cap and some tightening of hoses it went away.
Leave the coolant mix until your sure everything is ok

[PontiCad]

Ok, i went out and did a proper purge, took about 10 minutes until there were no big bubbles, only a tiny bit that collects after about 1 minute. Not the foam party i was seeing before. I doesn't have to be a HG i suppose, could be a loose hose or pinhole, right? Happy thoughts...Happy Thoughts.

Ok back to packing my house until tomorrow. Thanks!

Originally Posted by roscoFJ73

I would change the cap and be sure.
There is no way you could open the spring with your lungs even if the spring was weak.
When the thermostat opens ,you can feel the warm water entering through the radiator hose,its quite sudden.
Takes about 5-6 minutes from cold
I had some of that foaming and after a new cap and some tightening of hoses it went away.
Leave the coolant mix until your sure everything is ok

[MattF]

Originally Posted by PontiCad

I doesn't have to be a HG i suppose, could be a loose hose or pinhole, right? Happy thoughts...Happy Thoughts.

Worrying that it might be a head or gasket fault serves no purpose. If either of them is buggered, worrying won't make a jot of difference. Just working through the system methodically is always your best method of finding the problem. Rad cap and 'stat are two things which should be changed regardless if you're getting it dumping coolant or not pulling it back into the system on cooling. Then checking the viscous fan is okay, that there are no pinholes or blockages in the rad and also that all of the hoses are in good condition and sealing correctly. Water pump is always a possibility too. If it's still playing silly devils then, feel free to fear the worst.

Most problems with coolant systems tend to be the lack of maintenance though. If that isn't remedied early enough, it obviously leads to larger problems, as one would expect.

I keep telling them this on the Surf site, but do they ever listen to me? Rarely, if ever.

[PontiCad]

Thanks Matt, good advice.

I'm not that worried, just being analytical. Ok, and maybe a bit pessimistic...

Air is a pesky beast that finds its way into places it shouldn't be . Sorta like me looking under the hood of an import. lol.