PedalMaxer

99 c2 106kmiles. I have replaced the thermostat and the water pump. I believe I got all the air out of the system. Both radiator fans are working properly at both speeds. The engine compartment fan is working properly. It did overheat, but I don't think that the headgasket blew or the head cracked since the live data looks good, the engine sounds normal and I do not see any fluid mixing.

When I start it everything seems normal. The thermostat feels like it is opening at the right time based on the hose coming off it. The temperature just does not stop rising. After about 220 F all fans are running at full blast but the heat keeps ticking up. I shut it down when it hit 231F, probably should have done it earlier but I thought it might be leveling out so I let it get a little hotter than I wanted. I was thinking airlock, but I did the procedure pasted below and the coolant level did not really drop. Any ideas?

What I did to get the air out:
7. Fill with coolant up to the bottom edge of the filler neck.
8. Run the engine at idle speed and top up with coolant until no more coolant flows into the cooling system when the engine is revved moderately. (Coolant level now at lies lower edge of filler neck.) The coolant temperature must not exceed 80°C; proceed directly to the next work step if necessary.
9. Close reservoir and warm engine up to operating temperature at a speed of -2500 rpm until the thermostat opens after approx. 10 minutes (coolant temperature -90°C).
Check: The radiator supply lines and return lines in the front wheel housings must be hot.
10. Allow engine to run an additional 5 minutes at ~ 2500 rpm. Every 30 seconds, briefly rev up the engine to -5000 rpm. RPM surges are important for proper bleeding.

Ahsai

Did you mean your car didn't overheat before but it does now after the thermostat and water pump work? Did you manually open the black bleeder valve on top of the reservoir?

PedalMaxer

bleeder valve has been open since I refilled the coolant. This all started when a coolant hose blew off half way into a 200 mile drive. I replaced the clamp on the hose and replaced the water pump at the same time since I noticed some seepage. After that it was overheating still so I replaced the T-stat. When I did the T-stat the hose coming off it was empty so I thought I had found the problem. I feel the water start flowing at the correct temp with the new one. The new water pump looked fine and felt right when I spun it by hand before installation.

Hurdigurdiman

Do this

PedalMaxer

Thanks for the ideas guys. I just got in there and both sides look spotless. The front end was replaced a couple of years ago so they must have done them at that time and it has not been driven much since then. I am about to pull the condensers off to be sure, but I see absolutely 0 debris, not 1 leaf, unbelievable.

Ck986

Try a uview vacuum filler. I am no expert with filling these cars up with coolant but my prior mechanic left some air in my booster causing it to overflow. My understanding is that they are easy to screw up. I believe the vacuum system costs 95$ at ecs.

Youri Ko

Use AC Control Hack to get another reading of temperature, even though it does not represent what Duramteric would see.

Hold Recirc and Up for few seconds. Then +- to go to C6, then Center button to display engine temperature value.

Macster

Doesn't read like an air pocket. That the temp reading goes up suggests coolant is flowing through the system.

Even though the hose gets warm and suggests the T-stat is opening my WAG is the T-stat is defective, doesn't open fully.

When I did water pumps/T-stats I was taught to test the new one against the old one in a pan of hot water on the stove to ensure the new one opened at the right temperature and opened fully. The old T-stat was used as a base line as it was assumed it was working ok.

Techs do not bother with this test. They just assume the new T-stat works and most of the time, almost all of the time, it does work just fine.

But there can be that rare time when it does not work.

Right now the signs are the T-stat is not working right.

Are you sure you installed the T-stat the right way in the block? In some cases -- not sure the Porsche engine is such a case though -- it is possible to install the T-stat backwards and the result is the T-stat doesn't get the full blast of hot coolant and while the T-stat can open it can't open far enough to allow the coolant to circulate properly.

docmirror

I opted for the center rad, and the 160F thermo, plus I reduced the coolant mixture to 40%. I live in TX and don't plan to take the car anywhere it will get colder than about 0F, so the concern over extended coolant isn't warranted.

In addition to the extra cooling exposed to the air, there is also the factor of a greater mass of coolant vs the fixed size of the engine. Of course, the engine can be stressed more depending on driving habits, but the added fluid has damped any rapid excursions in temp that may have occurred before.

My temp gauge used to sit just to the right of the little wet bulb thermo, around the 0 in the '180' printing on the gauge. If I were stopped in traffic with the AC on it would go to the right some and make me concerned. Now, the gauge runs between the 1 and the 8 on the gauge, and it rarely gets to the 0 in the printing.

As an added bonus, having a cooler running engine, my oil pressure has gained almost half a bar in all conditions, and it seems that my fuel economy has increased slightly, which I can't account a reason due to cooler running engine, except the incoming air charge is also cooler, and thus denser.

PedalMaxer

The temp was always fine before this all started, so I think there is more too it than needing to beef up the system. I appreciate all the ideas and I think it sounds like a bad t-stat or maybe airlock are the current suspects. I will run it again and verify the temp with the ac trick, but I think it is at least ball park correct since the engine sounds a little different when it starts getting too hot.

I kind of doubt the t-stat, but I am out of ideas. It is an LN engineering 160 that I just bought. I tested it and the old one I pulled out in a pot before I put the new one in. The old one did not work until i actuated it with my hands. That seemed to free it up and it started to work. The new one from LN seemed to work fine and opened earlier than the old one. I dont think it would have been possible to install this type backwards.

If I do not get any more suggestions tomorrow I will drive it near my house and watch the temp, maybe that will get some air out. If that does not work I guess I will just pull the t-stat and see if it overheats without one.

fpb111

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DBJoe996

Do not run your engine without the thermostat! The coolant will circulate too fast and the engine will immediately develop hot spots, possibly ruining your engine.

Youri Ko

Few things to check out.
Is your system pressure tight? It needs to be able to hold around 15lbs. Is your cap pressure tight - same thing applies. Coolant needs to be compressed for the system to be efficient.

From my own experience - I have somewhat simillar situation to yours, the car would easily reach 100C, needle past center and it bugged the hell out of me, so in went MotoRad Low temp t-stat and vacuum refilled the system. Initially the system would climb to 80C (left from the middle) but once I'd hit streets and traffic, it would climb to pretty much where it was before changing T-Stat. Fans work fine. At that point I was running with the bleeder valve open. Next day I closed the bleeder valve. Right away I saw improvement, needle would stay longer close to 80C, and even when it climbed later on, it would settle around the middle. Open bleeder was keeping the system at 7psi and not 15 like it should operate.
Next step, 3rd Rad for me - I want it to stick at 80 all the time

PedalMaxer

I think this is solved. I need to top it off and try it from cold start tomorrow, but the temp in barely creeping up and the coolant is right at the min line. Thanks DB for the warning to not run it without the t-stat. I drove it around a little and that clearly got some air out. Something like what fpb suggested is probably the best way to go with these. I have had airlock problems before in this, but this time was different.

That procedure I had found to purge the air does not seem to be effective. Maybe having a load on the engine or bouncing and moving around on the road is what did it. Thanks for all the help guys, If I don't post tomorrow this is solved.