cooling problem

mytrplseven · mytrplseven's Garage

After complete front of engine rebuild, including new turbo water pump, my engine gets hot after driving a while. The temp gauge shows right around the first white mark regardless of how hot the motor gets. The fans run and shut off properly after shutdown. I did a cursory bleed after filling coolant and running the motor to what I thought was warm enough. Now after driving the car for about 10 minutes, the engine rattling starts and I shut it down. It needed more coolant. What gives?

kdjones2000 · kdjones2000's Garage

Read up on how to bleed these cars.

You need to get the front end up high in the air and the engine warm to get that last bubble out of the head.

That being said, how do you know it's hot?

mytrplseven · mytrplseven's Garage

Because it started to lose power and there was a rattling sound that isn't usually there and the fans ran for a long time. I was wondering if the gauge problem was due to an air bubble around the gauge sensor. The fans ran for a long time after shutdown.

grendiers · 07-27-2018, 07:15 AM

Is the thermostat opening up properly? When hot, did you squeeze the upper hose for firmness? Also, when hot, shut off engine, pull fan fuse, and feel radiator, is it hot?

mytrplseven · mytrplseven's Garage

All good information that I'll pursue. The one thing that still puzzles me is why the temp gauge isn't showing proper temp. But I'll research the procedures and run the tests and see where it goes. Thanks to all. Hopefully this isn't a head gasket issue.

mytrplseven · mytrplseven's Garage

Update: I found that there was a smaller thermostat that should have been in the old water pump for the turbo line and was not installed by the PO. Since this is my first experience with turbocharged 944's I missed it when installing the new WP. While doing research prior to doing all the recommended coolant cleaning and bleed procedures, I saw it on a parts drawing and said, "WTF"? So, now it's installed and the system has been drained (along with system flush cleaner) and refilled and bled several times with the front end elevated. All looks good now but will do a couple of final bleeds over the next couple of days. Thanks again to all who contributed their guidance in this matter.

kdjones2000 · kdjones2000's Garage

It's been so long since I have had that area opened up, I forgot about that thermostat.

Glad you figured it out...

911tracker85 · 08-05-2018, 08:53 AM

hmmm... good job figuring that out. I tend to read your posts, a lot of great work on that car.

when I got my 951, the PO told me it was a rebuilt engine. the belts and stuff on the front all looked good.

I'll probably do the TB this winter as this is now a 5 yr old build, just over 10k miles with about half on the track. did not encounter this issue on that job on the 944S or the 928.

was just at the 944fest at Nelson Ledges. but weekend got cut short do to some problem with my clutch. feel resistance on pedal but the clutch does not disengage. wont know the cause until I tear it down. installed all new clutch parts, spec alum flywheel/clutch/PP, and new throwout bearing, pilot bearing. only old part was the clutch fork, which is the current suspect. talked to a guy who had just one of the fingers break and had same symptom.

not to hijack your thread, but....

reason for the post is to ask if anyone has ideas on why my car tends to lose about a pint of coolant for every track session. does not seem to lose coolant for normal street driving. never see the engine temp get high. even on the track it usually sits in the middle of the gauge. have a LR oversized radiator and 3X oil cooler, and an override switch to engage fans manually at the start of a session.

so far have not seen/found any suspect location nor drips/leaks. earlier this year pulled the air cleaner box and check all hose clamps.

I now plan to take it to the main shop and do a pressure test.

I try to keep the coolant tank at the min level to avoid blowing it out the overflow. check between each session, but even if I let it drop below that, still seems to lose about a pint per track session. try to not let get to the bottom of the tank.

got talking to a couple 944 guys. idea of head gasket and other more serious issues were discussed. but the car just does not show any of the evidence/symptoms of those sources.

thoughts/suggestions for investigation?

soxnail · 08-10-2018, 09:50 AM

Higher temp and pressure during the track run, thus blowing it out of the overflow ?
Check integrity of the reservoir cap and do a static pressure test to Max 15 psi.
If no leaks depressurize and start the car let it warm up and run the pressure test again.
Sox

911tracker85 · 08-11-2018, 05:44 AM

a pressure test is my next step after I fix the clutch problem.

soxnail · 09-20-2018, 09:06 AM

Not some thing you wan't to contemplate, but coolant blow out under hard/boost driving can also be a sign of leaking head gasket.
When the pressure gets by the leak into the cooling system it can vent the coolant out.
Sox

911tracker85 · 09-21-2018, 05:50 AM

Quote:

Not some thing you wan't to contemplate, but coolant blow out under hard/boost driving can also be a sign of leaking head gasket

that was considered/discussed. but I never see any 'smoke' from the exhaust. now if it is leaking to the outside of the block/head... wont get to this until some time over the winter.