Out, dam'd leak

[BananaClip]

After a mystery cooling failure in march and a subsequent blown headgasket, my car is finally almost back to where it was when I started this year.

My real problem now is that it leaks coolant through the overpressure valve on the expansion tank. Whenever I park, it drains slowly but steadily, eventually forming a puddle about the size of a paper plate before it stops. In about two hours of driving around during the day i have to replace about a gallon of water. I'm pretty sure I'm getting it filled and vented right; I pour until coolant runs steadily from the bleed valve. Do I have to run the car while I am bleeding it once it is already hot? Whenever I try that it just sprays coolant everywhere. If I fill the block from the upper radiator hose, will I still have to get the car up to temperature and bleed it again after?

There is no coolant in the oil nor oil in the coolant as far as I can tell. The engine does have a slightly different running sound since the headgasket replacement- a slightly higher pitched whirring.

Slightly less worrisome is my power steering pump: it leans forward too far and bites into the lower radiator hose (the one with the wide upper end). The original M8x38 bolt (on the backside of the pump mount) was lost during the headgasket repair and I now have an M8x40 holding it up, but it still leans forward. Could this be a mount problem, or could the bearings just be worn to the point where the pulley's shaft is pulled out of alignment by the pressure from the belt? I figure if I can't get this figured out I can just get a really stout ziptie and pull the hose out of the way a few millimeters, but I'd rather fix the problem than work around it.

Can't wait to get this figured out so I can replace the clutch and transmission


Thanks

[Slam]

When I bleed the coolant, I open up the bleeder plug and run the engine from cold till I get a steady stream of coolant. Fans should cycle once and as soon as they stop I pop the bleeder back on.

As far as your leak goes, sounds to me like HG. Are you sure the head was flat when it went back on? Any machining done? Did the car overheat previously? Once can warp the head.

Sorry, I don't have PS.

[chrenan]

Hey Simon, when you bleed, cap on or off?

[Slam]

Clap on! Clap off! There's a dirty joke there somewhere.

Cap off for me. And if you're fearless you can blow into the coolant tank to force coolant out the bleeder. P-car mouth-to-mouth.

[John_AZ]

There are 3 different temperature radiator thermo fan switches for the 1988 944:
http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi?please_wait=N&forumid=&threadid=&command=DWsearch&description=fan+switch&I1.x=11&I1.y=12&FILTER_944M=ON&FILTER_TECH=ON&FILTER_SUPP=ON&FILTER_ACCE=ON&FILTER_CARE=ON&FILTER_STUF=ON&FILTER_PERF=ON&FILTER_MISC=ON&FILTER_GADG=ON&FILTER_TOOL=ON

If you have coolant leaking from the overflow your fan temp switch may be too high (95C/102C or 203F/216F). The cooling fan will stay on until the engine temp drops to 95C/203F. If you use a cooler fan switch, the middle one, the fan will stay on and cool your engine to 85C/185F and you may stop the coolant leak by having a cooler engine (18 degrees cooler). The cost to try is $11.75 from PP. Get a new gasket too.

NOTE: as noted the fan stays on longer without the engine running and this drains the battery. You must have a good battery and alternator charging system.
NOTE: Some may disagree with this practice because the engine does not get to optimum operating temperature.

Find out what temperature you have to begin with on your radiator.

I use the coldest one for my 1988 + 1987 924S ==75C/167F.
I live in an oven for 5 months and have no problems in summer or winter with overflow or engine performance.

John_AZ
1988 924S + 1987 924S

[BananaClip]

how do I know what kind of thermostat I have? I know I have a 92/ 102 switch right now.

[John_AZ]

Originally Posted by BananaClip

how do I know what kind of thermostat I have? I know I have a 92/ 102 switch right now.

I should have added in my prior post, do you think the thermo fan switch is working correctly or have the contacts arched internally and it should be replaced.


You probably have the stock temp of 80C/176F. This is the thermostat for the upgraded turbo waterpump (with the bar). There is no way to tell unless you remove it.
To make matters worse, there are actually 3 thermostats sold for our cars. 87C/189F and 80C/176F and 71C/160F. The PO or mechanic could have used any of these. Example: with the thermo switch you have 92C/102C the 87C thermostat may have been used even tho the stock temp is the 80C thermostat.

John_AZ

[onZedge]

Umm...did you try a new coolant tank pressure cap? It's cheap and I'll bet you don't even know how old the one you have is. Why does everybody think those things last forever?

[Slam]

Really good point. But I've never had one fail. Wonder why not?

[BananaClip]

I replaced the coolant tank and cap when the old tank failed, but the "new" cap is still really old. I'm going to have to take the hose on the water pump off anyway, so is there any way I can look on the thermostat when it is exposed? I know it isn't the original thermostat but I have no way of knowing which kind it is now.

[John_AZ]

I don"t know where you are on the project but I thought I'd ask another question. When you have the AC on (just put the key in and switch on AC do both fans operate?
This weekend the 1987 924S started heating up while driving with AC. I checked the passenger side fan and found NO 12V. The fuse was good. I pulled the AC relay ($40 Pelican) and swapped with a good relay. Worked-both fans ON! Repaired bad relay and good to go.

Good luck
John_AZ
1988 924S + 1987 924S

[BananaClip]

how does this even happen (endless overheating) is where i'm at now. fans function as they should, but to no effect.