SC runs hot 240 deg check internal thermostat operation with pics

[kodioneill]

I have a 82 SC always ran in the upper range of temps. I finally pulled the engine and internal thermostat after all the usual check first: timing, fuel,mouse,belt tension. I submerged it in water at 180 for 5min (1st pic) then 185, then 190 all for 5 minutes. Please give me your opinion on it's operation.

[Targalid]

I have seen this identical experiment done with cooking oil. Try that and see what happens at the temperatures you are seeing on the gauge, namely above boiling water up to 240, about 115C. (Wear an insulated glove.) Does it open all the way then? It looks partially open. Is there a piece of debris that prevents complete opening? Is it possible to use a pair of needle nose pliers to push it past that point while immersed to see if there is a rough spot on the valve? I would certainly be thinking seriously about replacing this part, about $40 if I recall. Amazing to think that the entire cooling system depends on this little part opening completely. I am really curious about this because I think I have the same thing and will have to pull the engine to do the same experiment.

[Joe Bob]

I have never tested an internal thermostat like that but I would consider using an oil based liquid that doesn't boil at a low temp as water.

T-stats are cheap. Replace it if you have doubts. Do you have an external t-stat and a trombone or cooler up front? If so, did you do a read on the temps in the external lines?

A good hand held pyrometer is a good tool to verify oil temps. VDO gauges aren't always right. T-stats should open at 185ish F. Unless doing 'spirited driving', oil temps should stay around 175-190F.

If after re-installation, with a new internal t-stat and you still show hot on the gauge AND you verified the reading AND you don't have an external cooler.....consider one.

If you have a trombone AND the external t-stat in the wheel well is opening at 180F, consider a brass row or Carrera finned cooler.....

[scotricker]

I just did that same experiment!

My SC has been running way too hot. So pulled the engine out and tested the thermostat just like that, only with cooking oil. see my thread "boiling oil". My thermostat never moved , not even a little bit. I found a used one from the forum classifieds, or you can get a new one from Pelican for 175.00.

I did the same test, side by side, with the new one and the one that came out of the car. The new/used one opened at around 180, and the old one never moved. Now I have a cool aluminum paper weight!

It looks to me like you need to replace yours. get a new O-ring too.

S.

[Joe Bob]

Porsche 911 & Carrera Main Engine Components - Page 8

Currently $155.

[kodioneill]

Yeah I have a IR thermometer checked the trombone lines and tank all about 240 deg.

[Joe Bob]

Then proceed, you are going in the right direction......

[boyt911sc]

Check if your auxiliary thermostat is open @ 185°F. At around 175°F, the engine thermostat should be partially open and starts circulating the warm oil from engine to oil tank. Both these oil thermostats should work like clock to get good cooling.

Tony

[boyt911sc]

Originally Posted by Targalid

I have seen this identical experiment done with cooking oil. Try that and see what happens at the temperatures you are seeing on the gauge, namely above boiling water up to 240, about 115C. (Wear an insulated glove.) Does it open all the way then? It looks partially open. Is there a piece of debris that prevents complete opening? Is it possible to use a pair of needle nose pliers to push it past that point while immersed to see if there is a rough spot on the valve? I would certainly be thinking seriously about replacing this part, about $40 if I recall. Amazing to think that the entire cooling system depends on this little part opening completely. I am really curious about this because I think I have the same thing and will have to pull the engine to do the same experiment.

You can't get the water to boil @ 240°F at room (kitchen) condition unless you use a pressure cooker or autoclave. For testing opening temperature of the thermostat, a water bath is sufficient. An oil bath would have a much higher temperature range than water.

Tony

[ruwoodbury]

Is it necessary to drop the engine in order to replace this thermostat? My car is running a bit too warm as well. It was reaching around 250 degrees maximum (a little above that when I was chasing my son in his '12 Mustang GT up a mountain pass at 90-110 mph).
I've started with the oil cooler, making sure it was clean, replacing the seal and installing a 200 degree fan thermostat. It's running 15-20 degrees cooler when driven easy and the max temp has dropped by around 10 degrees. Tomorrow I'll put in a new plunger/regulator in the external thermostat to see if that helps.

[kjchristopher]

Originally Posted by boyt911sc

You can't get the water to boil @ 240°F at room (kitchen) condition unless you use a pressure cooker or autoclave. For testing opening temperature of the thermostat, a water bath is sufficient. An oil bath would have a much higher temperature range than water.

Tony

That's his point.

[uwanna]

Originally Posted by boyt911sc

Check if your auxiliary thermostat is open @ 185°F. At around 175°F, the engine thermostat should be partially open and starts circulating the warm oil from engine to oil tank. Both these oil thermostats should work like clock to get good cooling.

Tony

The thermostat being open or closed only decides whether the oil takes a trip through the cooler or not. The oil allways returns to the tank regardles of the position of the thermostat.

[Targalid]

"Yeah I have a IR thermometer checked the trombone lines and tank all about 240 deg."

Can we conclude from kodioneill's observations of 240 at tank and trombone oil lines that the bulk of the cooling takes place at the main engine cooler? In other words, does the external cooler only augment the engine mounted cooler rather than providing about equal heat exchange?

[Joe Bob]

The engine circulates to operating temp and the internal t-stat is supposed to open....if it doesn't open until 240+ then that's what everything is and stays that way.....the internal t-stat is the master controller (Tron). It will come back a little cooler depending on the downstream lines and trombone in this case.

Just because the external t-stat is working doesn't mean it will effect (affect?) the engine operating temp. Clear?

[Reiver]

Originally Posted by Targalid

"Yeah I have a IR thermometer checked the trombone lines and tank all about 240 deg."

Can we conclude from kodioneill's observations of 240 at tank and trombone oil lines that the bulk of the cooling takes place at the main engine cooler? In other words, does the external cooler only augment the engine mounted cooler rather than providing about equal heat exchange?

I believe it does from my experience...the trombone doesn't do much at high ambient temps. Hardly made a diff in my engine temp after the initial dumping of colder unheated oil into the system...then jumped right up after that was hot.
If you change it out to a latter Carrera radiator/block off and fan then it does a great job. Night and day difference.

[Joe Bob]

The brass row cooler does a good job, close to the Carrera radiator type. I've seen them use a fan as well.

[bryanrex]

I'm reposting this here because I know I'm not the only one who has experienced hard to track-down oil over-heating issues:

I just purchased my first 911 SC and it also had a known oil overheating issue when driven hard. The car was 95% restored so I bought it anyway and decided to tackle the project. Under normal conditions the oil temp would remain at about 210, but when driven hard the oil pressure gauge would begin to twitch and act erratically (due to cavitation) and the oil temp would rise to nearly 300!

Here's what I did to troubleshoot (in order) with the problem persisting until the final step:

1) I grabbed the front trombone cooler to check for heat. It was getting hot so the external oil thermostat was OK.

2) I removed the fan to check that the engine oil cooler ramp was free of blockages. It was partially clogged with sludge, so I blasted two cans of degreaser on it and on the cooler itself (from the the top down). During reassembly make sure you properly orient the shroud behind the alternator. Also clean your fan while it's out (sand blast, then powder coat and polish). Unfortunately all of this didn't prevent the overheating (still saw 280 on the oil), but it did improve the looks of my engine bay. Photos below.

3) Assuming it to be the engine oil thermostat, I removed it. On this car there is no need to drop the engine. I did it in 2 hours with an endoscope, a mirror, and a few extensions. First pull the AAR vacuum pipe, the intake air plenum and disconnect the breather hoses from the oil tank to help gain access from the lower right side of the CIS. Pulling the thermostat out of the hole was the hardest part, but since the thermostat is lipped you can use a $10 O-ring gasket removal hook to pop it out. I checked the thermostat using a stove (see photo below) and it was functioning perfectly. Also, replace your gasket with the green one pictured.

4) At this point, with everything properly sorted I was almost resigned to the fact that this was a design flaw and I would never be able to track the car... until I read the TSB mentioned in this thread. The 78 and early 79 models shipped with an improper oil pressure relief valve and a bad sump pickup which caused the sump to flood, improperly scavenge, and cavitate. I replaced the rubbish with these parts, solving the issue:

999-064-026-01-M260 Oil Pressure Relief Cap
930-107-533-01-M100 Oil Pressure Relief Sleeve
930-107-531-01-M260 Oil Pressure Relief Spring (Vertical)
930-107-314-00-M253 Engine Oil Sump Screen
PEL-RW-SP Vintage Aluminum Sump Plate

I can't believe it took me almost a week to figure that out. This is my very first Porsche, and although I have lots of experience building small block Fords this is definitely not the same. I'm glad I have experience, because this thing is an incredible mess of vacuum and oil lines! Elegant engineering though.

Oil cooler air ramp on right


Alternator wiring in case you forgot what goes where


Man, that is NASTY!


Now we're cooking with gas!


The engine oil thermostat is somewhat difficult to remove, but with skill it can be done with no drop, partial or otherwise.


Here it is functioning to spec. Fully open at about 186.


This is what makes all that hard work worthwhile. Very rewarding!

[T77911S]

mine went bad too. the give away was my oil temp would slowly go up, but never go down.
i think i boilede mine in water and found it was bad. '

put in a NEW one. i would not putin a used one just because it is a pain to get to.

i took my motor out to do mine but also check my cam timinng since i suspected it was not right, and it was not. also did a valve adjsut

[burgermeister]

You can repair the internal tstat using the expansion element from an external tstat:
http://forums.pelicanparts.com/911-engine-rebuilding-forum/689055-internal-oil-thermostat-repair.html