Art20c

when it idles, does the coolant go way above normal level in expansion tank and when you rev the engine goes back down?

928ntslow

No, not at all.

Art20c

Reason why I asked was that I had 944 turbo with exactly the same symptoms as you have plus that thing with coolant level. Problem was the head gasket. So, I think you can eliminate that possibility.

mark kibort

when the t-stat doesnt open, it will have the symptoms you talk about. I have this issue sometimes with my race car. its an intermittant issue, based on how full my overfilll tank starts out. if it is half way, its more likely to happen than when near full. I think it has to do with the ability for the t-stat to get heat soaked. ive replaced the t-stat several times and it hasnt changed this issue. how i can test my problem, is that i also feel the bottom of the radiator, and its cold and the top is hot. car will overheat, unless i turn off the car for 30seconds and then restart. Then, the temp will fall and radadiator get hot. (like its supposed to ) . Im careful about getting the air out of the system as well.

try an overfill of the overfill tank. (more near the top than normal) and see what happens.

also, i should note, as long as the car was warm, this problem never happens. seems like it is a classic t-stat sticking issue, or a water level issue (i.e. even though you burp the system , there is still a high point in the system that has reduced flow or water near the t-stat adn the t-stat doesnt see the heat to open)

mk

928ntslow

I really don't know how to react to the results I had found today.

I had removed the water pump and found that it was intact and the impeller was securely attached to the shaft and pulley. However, the impeller was very rusted!

A couple of observations were, this does not look like a factory WP, though it does have the part number casted into the body (not that that that means anything)...looks more like a pump from a later car, but the idler pulley post is different. The water channel for the pump was stained a little from the rust, but is virtually in perfect condition. There is some calcification, but it seems minor. The crud you see on the pump (and some on the block) is not all hard..more like gooey snot! ...lol Why in blazes would the impeller rust????? After market Chinese WP made of tin???

So it seems that the water pump has been pumping. I did notice a black streak on the pulley, but again, that doesn't mean anything. Who ever put this pump in goofed up a bolt hole and never bothered to fix it.

Now for the "UH OH" news. I went to drain the block and removed the driver side bolt. NOTHING came out. I removed the passenger side bolt...NOTHING came out! YIKES!!!!!!!!!!! My thoughts are the water channel in the block is ...uhm...blocked! This would explain the no flow and the overheating.

BUT...why would the heat work after I revved the engine since the valve is at the back of the block? Why would the engine run cold enough to operate for a while and why would the coolant flow once in a while?

This is the first I have attempted to drain the block. NO, I have not tried to run any water through the engine to see if it drains through the holes. I hadn't had a chance for as soon as I pulled the WP and pulled the drain plugs, I had to go to a meeting.

Give it to me straight, if water passages are blocked, can I free them up somehow? Would compressed air or pressurized water clear this? I was thinking maybe debris in the water passages has settled near the bottom of the block and I could make a fitting to blow the crap back out to the top from the drain holes.

You would think if it was a result of hard water, it would be evident in the WP area. My old US 82 had hard water corrosion and worked just great.

This car is a test from the Porsche Gods I tell ya!

Thoughts?....

Bill Ball

Hi Keith:

I don't mean to insult you, but are you sure you pulled the block drains? The plugs are rather distinctive, but who knows. The plugs for the exhaust temp sensors might be confused with them.

I gather the coolant drained from the radiator and WP isn't all rusty, but if the block drains are clogged, there is a chance there is rust lodged throughout the system.

928ntslow

Yea, I know, ya gotta ask. Yes, they are the drain plugs on the block. The butt ends of the plugs look black but are not greasy or sooty...just that color for some reason. Could be magnetic material.

marton

Random Thoughts
For the impeller to be rusty like that there must be air in the system; did you ever do that experiment in school where you leave a nail covered in distilled water & it does not go rusty?

Sounds the best approach to me. I would use water & not too much pressure; I mean like a garden hose. I assume the water would come out of the bottom hose conenction so you may want to organise something to lead the water to a drain.
Maybe you could find some suitable tapered plastic part for the hose that you could screw into the drain hole, the threads would probably cut a thread into the plastic.
I assume you did not have time to try poking something through the drain holes to see if you could clear anything?

Thinking positive; when I put the drain plugs back in I always wrap them with that white plumbers ptfe tape then they are easy to remove in the future.

Marton

Bill Ball

You added those pics after I replied (or I somehow missed them)...THAT'S NASTY LOOKING. Of course, the impeller is cast iron. You've seen them before - they are usually clean as a whistle if the corrosion protection has been kept up with frequent coolant changes. The pump must be original, and at some point in the long life of this car, the cooling system was abused, left almost empty, sitting for a long time.

AO

Old Green coolant = bad juju!

Get that stuff out of there. The Green coolant does not like the aluminum in the heads.

If the block isn't draining, then I'd say you've got some issues that need to be resolved. I never looked inside the drain passage on the block when I had it out, but maybe a oil passage brush might get in there and loosen the obstruction. Coolant should flow through. I would flush the hell out of that block and cross your fingers.

Oh... and put some orange coolant (or at least one that plays nice with aluminum) in there.

heinrich

I'm sorry Keith that is not looking good. Do we think the head gaskets are OK?

Dennis Wilson

It is obvious your system needs backflushed. I prefer flushing the radiator, block and heating core separately. Trying to flush the whole system at one time is difficult due to the thermostat. If left in, the radiator is flushed improperly and if taken out the block is not adequately flushed.

Dennis

ErnestSw

Just a guess, but is it possible that some PO used some kind of gorrilla snot to stop a radiator leak and fubared the cooling passages?
The narrowed and coated passages might explain the need to rev the engine and increase the coolant pressure to force it into the heater core and the initial cool running and the inability of the engine to maintain its cool.

marton

If they were only narrowed then I guess the fluid would drain out when the drain plugs were removed; it does not.
It sounds like something is stuck in there (but strangely both sides?). It is either acting like a valve so it is forced open when he revs the motor or the water is finding another path when he revs the motor (which would support the gorilla snot theory).

Myself I do not know enough about how the water passages are laid out to know if there is a single point that could be blocked or if there are alternate routes...

Marton

BC

The green coolant could have corroded some things, and therefore the system had particles in it. Then the car could have sat for quite a while - did it sit?

It will settle right where that drain plug location is.

Even with the proper coolant, there is residue in the passages. Mix coolants, and I think the white stuff could help the real corrosion stick to the areas it should not be.

A WARM water flush, maybe even with some simple green, may do it. I would stick a screw driver into the drain holes and see what you find.

Also, the metal pipe on the passenger side can corrode quite badly as well.

I think the issue with the heater core is that it is full of crap too. Infact, some of this crap could be blocking some of the entrances there, and when you rev, you create some more pressure that opens some clogs temporarily, not all of them.