Bill_396

First attempt at driving my 86' 951 through a Michigan winter. Has been going well except for when the snow gets so deep the front valance plows annd the snow shoots over the hood and covers the windshield.
Noticed several times momentary loss of heat when the water level was okay. About a month ago in a traffic jam on the e-way lost heat and temp gauge started to rapid rise. Got off the road before the warning light came on but it was in the red. Once it cooled I did have to add a few quarts of coolant and I also bleed the air to be sure it wasn't air-locked. Was fine for about a week then about twenty miles from home on the e-way again noticed heater go cold and temp rapidly rising. This time I discovered that I failed to tighten the bleeder enough and had been seeping coolant there, could smell anti-freeze when I would shut the car off. Added coolant once it cooled and it was fine. Thought that was the problem. Now I have been checking the coolant every time I take off, no loss and no more antifreeze smell.
This morning about ten minutes from my house heat goes and temp shoots up. Stoppped and rechecked coolant, was still at high mark. Once it cooled I filled it to the cap but that did nothing. Limped back home coasting and cooling down to keep the warning light out. Still had no heat. Today I suppose the t-stat could have stuck closed except I did have good heat at first. Any chance the pump bearings could be going out and finally locked up for good? Lately I thought there may be a new noise under the hood but not for sure. When it first overheated I thought maybe the head gasket was letting go, have been running 15 psi + for close to a couple years (MAP-II, K-27, 3", Deltagate). Have been watching the off boost vacuum, same as always, no white smoke or milkshake in the crankcase either. HELP! Next step will be to check and see if the pump is locked but it may have fixed itself again. Any suggestions would be appreciated, thanks, Bill.

Luis de Prat

Bill, it sounds like you did not bleed the cooling system after topping off the reservoir. Did you? A failing water pump makes a distinct "whining" noise. Is that what you're hearing?

If not, park the car on a hill facing upwards with the parking brake on. Turn on the engine and open the bleeder plug until straight coolant comes out with no air bubbles.

Clean up any spillage with a rag, since coolant is toxic for animals.

Good luck.

Bill_396

Luis, I have not bleed it every time but several times. In a downpour this morning I cracked the bleeder open and got immeadiate coolant. Wasn't really a whining, more intermittent than that. I'm at a loss. I have not tried bleeding on a hill though, maybe I should check that. thanks for your response, Bill.

Luis de Prat

Forgot to add that you should also crank the heater (interior) to max when bleeding the cooling system.

An intermittent whine could also be the pump, but there are too many similar intermittent noises in the engine for me to guess.

With the engine on, open the hood and put a long screwdriver on the waterpump housing. Put your ear against the handle and see if you hear any abnormally loud grinding. That would indicate a failing waterpump.

mochman

that distict whining sound is usually the t-belt getting ready to frag

Porsche-O-Phile

I have a similar problem right now with my 951, which will be coming off the road tonight until I get this figured out:

I recently replaced the turbo water pump and coolant reservoir (nice new clean one). I've noticed, similar to Bill, that I drop between 2 quarts and a gallon of coolant per day (that's between 70-100 miles for me). I similarly bled the system and have watched for obvious "staining" or other indicators of where it might be coming from - no luck. I also bled the system per the procedure in the owner's manual - no change. This has been going on about two or three weeks now. My suspicion is obviously the area around the turbo pump or the coolant reservoir, but I've looked pretty carefully at all those areas and see no evidence of coolant leakage there. I'll look again when I can actually get it up on ramps, get the body pan off and just watch it while it runs.

Where the hell would several GALLONS of coolant go without noticing it? I have no white smoke whatsoever, so it isn't burning off.

theedge

Stuck t-stat would result it loads of heat and rising temp gauge, since the only path "past" the t-stat would be throught the heater core. Been there, experienced that.

Loss of heat and rising gauge seem to indicated a bubble. Bleeding 951s is a major PITA, and when you think youve got it, it can fool you.

You need to let the car come up to operating temp, and have the heater on full heat. Facing uphill or being on ramps will help too. IMHO dont run the car up on jackstands.

Porsche-O-Phile

Yea but a bubble wouldn't take quart after quart of coolant; it'd eventually burp the bubble out. What I'm saying is the capacity of the system is finite. You can only add so much coolant - period. Unless there's a leak somewhere.

Bill_396

I brought it in tonight and by then the coolant was low again. Filled it up, then warmed the engine, the water is definitely not circulating. Gauge showed temp past half way but the hose hooked to the end of the head was still cold and no heat. theedge, I hope you're right about the stat because it appears to be a bitch to remove. Wasted over an hour ruining cheap snap ring pliers trying to get the clip out. Finally got sick of the tips turning so I tried to MIG them in, oops, too much heat, the end of the pliers disappeared. Any chance the pump isn't turning. Wouldn't the belt make a noise?

Porsche-O-Phile

If the water pump is siezed, you'd certainly hear the cam belt squealing on it - before it breaks.

DHC8FO

I had a simular problem that started out as a bleeding issue, and could'nt resolve. I wound up replacing the internal thermastat and that resolved it. I did test the old one, and it did open, but at a higher temperature, and not as fast. Haven't had a problem since. It certianly can't hurt, and it's not that expensive.
-For what it's worth

Luis de Prat

The radiator could also be clogged and/or leaking. Is it the original unit?

Bill_396

Don't know the cars history prior to my purchase three years ago. Appeared to be well maintained. Had all the factory updates I'm aware of including "late" style pump. When the coolant flows normally it always runs on the bottom of the temp gauge. DHC8FO, do you mean the thermostat in the water pump inlet? How did you get it out? I assume that you need some very good large right angle snap ring pliers, correct? Did you have to remove that coolant pipe/brace/support that runs across the front? Thanks all for your help, at this point air lock sounds most likely but I would like to also change the t-stat while I can see it if I could just get the thing out. Bill

Luis de Prat

Some good pointers on the thermostat R&R here (check under shop manual):

http://www.clarks-garage.com

DHC8FO

Yes I was referring to the thermastat in the water pump housing. It's pretty easy to replace with a modified angle pliers. I ground the tips down wit a dremmel tool to fit into the retaining ring holes. Also, the thermastat I removed was not a porsche part, the dealer part was less than $30 so I went that route. As you noticed our cars cooloing systems are a little different that most, that is why I chose the Porsche part, I knew ther would be no issues with it doing what it was supposed to, and from the standpoint of trouble-shooting you know it's 100% and can look elsewere for the problem if it remains.