Markoneus

Thx for all the suggestions and perspective, gentlemen. Really appreciate it.

@ David Floyd, well, you may be right, though I sincerely hope not. I'm in NYC w/ no garage of my own, no tools, so I outsource my labor beyond basic stuff. I'm told this could be $2-3k in labor through a lot of shops, no? Any estimates?

David Floyd

Go thru the check list that Tom posted hopefully you can find something more simple, as far as an estimate it will be mostly labor charges, $200 give or take for parts, not sure what book hours it takes

KevinGross

I agree with Tom's advice. Would add that if you suspect the head gasket, get a "block checker" kit from the auto parts store. Very simple device that checks for exhaust gas in the coolant.

Kevin
Catellus Engineering

boerge

Does the temp gauge move if you turn heater fans on/off, ac on/off?
I have something similar to what you are describing, my plan is to change radioator switch, I think there is only one. Mine never blew hoses though, and during constant cruising in 4th/5th gear it seems to be fine.
I changed water pump and thermostat beacuse of these things, but it still does it. I've even suspected a plugged radiator as the car was sitting still for some time, but not sure. I will change the radiator switch first, then possibly the radiator. If it doesnt help I'm guessing HG is next.

Markoneus

Update:

They replaced the 2 new torn hoses, and replaced some worn out connectors that were connected to the crank-position sensors. Now the car is no longer fully overheating, but it stays @ 3/4 temp, whereas it was always mid-range before. And they've checked the coolant twice for flourocarbons now, and found none either time. So hopefully it's not a blown gasket, and they're looking at other possible problems now.

ps: found out the gasket was actually a Wildfire, part # 951.104374 HD
Anyone got any intel on those?

Still accepting other theories.

lart951

those wildfires are crazy

Turbo17

My '86 began occasionally overheating at around 150K. It was the radiator fan switch.

User 52121

Are you sure the cooling system is fully bled?

Markoneus

Yeah, the system is bled fine. The mechanic who's working on it is a 944 S2 owner himself, works on these all the time.

@ lart951 : Why do you say the Wildfires are crazy? What's your experience w/ them? Anything in particular I can be on the lookout for?

dlr944

Do you notice any excess white smoke out of exhaust?

Tom M'Guinn

Lart was joking. Those HG's are known as "widefire" gaskets. The "wide" refers to the wider sealing ring for the top of the cylinders. Wild fires are burning out of control in the southwest, probably prompting Lart's comment....

Markoneus

Yes, sorry, it's a WIDE fire, not wild fire. But yeah the mechanic just reported back again, and for the 2nd time, there were no flourocarbons in the coolant, and no, no smoke out back/ from exhaust, so he's convinced the head gasket is fine, and he's now going to try a new thermostat. will report back with results. Thx again everyone...

951kaos

If the system is properly bled; check to see if the fans are coming on at the right temperature, maybe a faulty switch?. Also check to see if the coolant tank is not cracked and another cheap fix is to replace the coolant tank pressure cap. I experienced overheating after a water pump/timing belt replacement. Replaced the new thermostat with another new one and it still was running hot. Turned out to be the coolant tank cap (cap and tank were replaced 2 years prior to belt replacement) was not maintaining pressure.

schip43

No one has mentioned the radiator cap? I lost the head-gasket on my 944 N/A directly because of the rad cap. It was worn out and on my list of things to do!

I would think if it's been in and out of the shop if it were bad someone would have noticed but....

Markoneus

Just got another report back from the mechanic:

They now thing it IS the head gasket. I said they weren't getting any hydrocarbons when testing the coolant fluid before, but this time they tested it on a cold start, and got a high reading: 155 (ppm, I think), and then it went down to about 90 once it warmed up. So, the theory is that once the engine is warmed and there's been some expansion, the leakage isn't as bad.

So, looking like it needs a new gasket. Ugh. (they found this out before putting on a new thermostat, so no money wasted there, and yes, tested the caps and they were fine, and the coolant tank had no leaks)