T-Stat Question

[adamred]

Posted this at the end of my last thread but usually that last question gets missed if it post drops to the next page....

If the rear t-stat fails will the engine if it is in a good state of tune stay at a reasonable temperature (in normal day to day driving) or does this failure generally cause the car to rapidly overheat?

Just trying to do a little non-invasive diagnostics. Thanks.

Adam

[Formerly Steve Wilkinson]

I have no practical experience with this, but I can't imagine that running an SC with the thermostat failed in the closed position would lead to any kind of extreme rise in heat under normal-temperatures, normal-duty-cycle driving. After all, aren't there plenty of earlier Porsches that don't even have front oil coolers?

Stephan

[targa80]

I think a failed thermostat in the closed position in a 3.0 would be a bad thing. The reason for the added trombone oil cooling with the T-stat was to help cool the oil due to the increase in heat generated due to the larger engine. As the engine liter size increased they went from the trombone to the radiator with the fan to push more air and cool the oil more. What would happen to a 3.6 L with a stuck T-stat? If it's broke fix it, if you don't a rebuild on an overheated engine could be very expensive.

[adamred]

Absolutely, agree, want to fix it if its broken.

I've heard they can be a b***h to get out.... any way to diagnose without removing it? Or do you need to immerse in hot water to check if the tstat opens to difinitely diagnose?

Adam

[kstylianos]

Adam,

The t-stat is not too difficult to diagniose. If its opening, then the trombone will be warm-hot depending how long the engine was running after the t-stat opened. Just feel the trombone after a decent drive with temps over 200 degrees.

If its cold, then either the t-stat is not opening or you have close to 100% oil restriction to/from the trombone from crimped lines (oil not circulating). BTW: Both of my lines were cripmed pretty badly in multiple places, but still had decent flow to/from the cooler as it did get pretty warm. I replaced them with the Elephant lines anyway.

To R&R the thermostat, it obviously needs to come out of the fender well. Its suspended by the 2 hard lines in front the 2 lines from the engine. Soak the fitings w/ PB-Blaster nightly for a week or so, obtain the proper 32mm wrench. The hard lines will probably need to be unbolted from the car (underneath the rocker cover, which has to be removed as well), including the connections at the trombone to give you more 'wiggle room' to access the front most connections. Hopefully after soaking and good leverage the connections will break free w/o damaging the AL threads on the t-stat housing. Once the t-stat is free, take it to the bench and remove the side slotted cover, this is actually the thermostat mechanism. The bottom slotted cover holds the pressure relief. You can submerge in boiling water to test it, you should see it open.

Alot of work to truly test the thermostat. So if you feel any warmth at the trombone, its probably working.

[BK911]

Run the car until it reaches operating temperature and touch the oil line. If it's cold the t-stat didn't open.

Good luck!
BK

[Elombard]

I have an sc motor in an early car with no Oil cooler. It is fine unless I go on the track. I dont htink you would have an immediate problems in normal day to day driving.

[adamred]

Thanks all:
Posted this issue yesterday the issue was that one line seemed hot the other cool, tomorrow after a good run I'll carefully check the trombone itself to make sure its hot.
Truthfully of all the 911 issues the engine temperature is the one that gives me the willies...

Adam

[kstylianos]

Originally posted by adamred

Truthfully of all the 911 issues the engine temperature is the one that gives me the willies...

.....as it should

[targa80]

I usually have to wait until the temp is just past or has been on the first mark in the temp gauge for a while before my T-stat opens. If you are running beyond that and the trombone is cold then you have a problem. Check as mentioned earlier for crimped lines undercar towards the trombone before going after the T-stat.

[Silveresrty911S]

I've been running a 3.2 with my mid year car and havn't seen any temps above 225, that was when I was stopped in traffic for about 20 minutes on a warm day and wasn't going more than 5 mph. It has no cooler to date but is close to getting one in the next month or two. Any track time or long periods in slow traffic on a HOT DAY would scare me, that is why oil lines and a fender cooler is in my future

[adamred]

OK just an update. Ran the heck out of the car this weekend, everytime, jumped out when I got to my destination and the trombone was hot to the touch, so the T-stat should be OK and the lines (although dented seem to be flowing).

Then realized that the car stumbles quite a bit when starting up, called upon my Pelican knowledge that is slowly building and realized that the car must be running lean...sure enough went to my wrench today, he concurred and did a quick free adjustment.
I love easy solutions....Thanks.
Adam

[kstylianos]

How are your temps now after the a/f adjustment?

[Wayne 962]

Be careful when touching the oil cooler lines - they can become VERY hot...

-Wayne

[adamred]

Charlie:
Didn't get to have a full run, the shop is only 5 miles or so from my office, how convenient.....but ran quickly there, left it running the whole time I was there and a nice sprint back to the office and it ran at a more familiar 190 (right below the first line)

I'm the master of getting burned (kitchen, fireplace, etc) so I was real careful with the oil lines and trombone....thanks for the advice....

Adam