strange overheating problem

[wingman]

ok i've looked into this a little bit, and not once have I seen another symptom like mine. When I start the car up after it's had a small amount of time to cool down, or from when it's dead cold, my temp gauge will slowly (1min-2min timeframe from normal op. temp.) climb all the way up past the red and suddenly (as fast as the gauge will fall) drop down to normal again,...I've figured out that the harder you push it, the less time it spends up in the danger zone. It doesn't happen ALL the time, just every 2/3 times the car is started. When it does do it I can get out of the car and squeeze the upper radiator hose flat, indicating there's no pressure....but after 20+ minutes of driving after it happens, or when it never happens, the system seems to hold pressure fine.

At first I thought it was a bad thermostat, so I replaced that, the radiator cap, and the coolant at the same time. It still did it

I've checked every eaisily accessible area for leaks, and everything looks fine...no huge puddles of coolant on the ground or anything like that. However when I turn the engine off I can hear a faint hiss from the area around the ISC and TPS...there is a known vacuum leak from between the ISC and manifold, but I don't think that has anything to do with it.

I've think I've figured out that it has something to do with the pressure in the system, being that when it happens the overflow will have a very small amount of coolant on the top of it, indicating that the pressure is rising enough to push it from just below the full level out the top...and the upper radiator hose has no pressure afterwards.

I'm fearing BHG...but would one spike, then normal operation be a symptom of this? After the needle falls I can boost it to hell and back and it'll still be fine, it's just until that point that there's problems.


Edit: and just so everyone knows, I have an HKS 2.0 MHG and ARP studs

 

[johnathan1]

hmm, could very well be a BHG... the pressure from the cylinders(exhaust) enters the cooling system, causing the bottle to overflow...blah, blah...

Also, check for leaks some more...those worm clamps have a tendency to loosen up a bit after they have been taken off/put on...

ISC huh? check the coolant lines to the ISC... maybe tighten the clamps, or replace the hose if it looks like it needs it...

 

[wingman]

I pulled the ISC off a few weeks ago when I was fixing some idle problems...the hoses looked fine and the clamps are most definately tight. I've checked all my heater connections, and from what I can see by the T-stat housing it's fine in there. The passenger side of the block looked a little bit damp some time ago, I'll have to check it again next time I go out though.

And I did check my codes...51 was the only one I got, which was expected because I have no A/C

 

[johnathan1]

Did this problem start after you removed the ISC? Passenger side, huh? Check the clamps on the the heater hose that comes straight out of the back of the head (up against firewall) and check the hose elbows that connect at the front and back of the head... Also, take a look at the cap that caps off the hardline (was used on JDM cars only, was blocked off for USDM...)

 

[wingman]

Did this problem start after you removed the ISC? Passenger side, huh? Check the clamps on the the heater hose that comes straight out of the back of the head (up against firewall) and check the hose elbows that connect at the front and back of the head... Also, take a look at the cap that caps off the hardline (was used on JDM cars only, was blocked off for USDM...)

yeah, as a matter of fact...not immediatley after, but a week or two. I just got back from giving it a really good look through, and it looks like there's a small leak next to the lower radiator hose, specifically the smaller hose that sits right above it and takes a bend towards the block. I've never had to replace that one so I don't know how much of a PITA it is, but any advise would be appreciated. maybe that's letting air into the system and causing all my troubles, and would explain why my overflow bottle drains in about 3 days.

 

[johnathan1]

yes, that would explain it, which hose is it exactly?

 

[IJ.]

If the system is sucking in air it could be an airlock and what you're seeing is a temp spike as the steam builds up then the T Stat opens and water flows enough to bring the temp gauge down!

The scarey/sad part of this is that it's a perfect way to anneal an aluminium head

 

[wingman]

If the system is sucking in air it could be an airlock and what you're seeing is a temp spike as the steam builds up then the T Stat opens and water flows enough to bring the temp gauge down!

The scarey/sad part of this is that it's a perfect way to anneal an aluminium head

That's along the lines of what I was thinking...but oh god don't even go into the horrors of annealing the head...looks like I'll be ordering some hoses and clamps here soon. I can't afford to toast anything major right now...it's my DD for the moment

I'll burp the system after it cools down and see if it helps it any...never hurt anyway.

 

[theDon]

have you checked the fan blades/fan clutch/water pump?

 

[johnathan1]

ugh, my car has a VERY slight coolant leak coming from the lower radiator hose, where it meets the thermostat housing... jeez, will a NA radiator hose work on a Turbo?

 

[wingman]

have you checked the fan blades/fan clutch/water pump?

fan is fine, all 10 blades...the clutch gives some resistance, and it spins about 160-170* when given a good push, which I guess is in spec.

I don't know how to test the water pump...the belt tension is within spec though. One buddy of mine says he had the same problem on his N/A and it ended up being the water pump, but another buddy tells me it's probably a BHG.

I'll report my findings after I test the coolant for exhaust gasses and replace those hoses....I'm a little broke right now so that might be a while though LOL

 

[wingman]

ok just tried to burp the system...don't know what this means but it'll warm up to temp, then periodically blow a good bit of coolant out the top. Not violently, but enough to send it 2" over the outlet. Goes back down to regular level (1 1/2" below the rim) I don't know if this is just a metric crapload of air in the system, or if it's exhaust gasses pushing them up from a BHG.

whatever it is I don't think it's good


update: Tried the burping thing again...this time it didn't spew coolant all over the place, but now I'm positive there is some kind of leak in the system...i burped it for 20 minutes and a small amount of air was coming out of it that entire time. Eventually I just said screw it and put the cap back on. I'm starting to think BHG more and more, but until I get the test kit I'm not certain.

 

[IJ.]

Not sounding good Wingy