911 thermostat won't open

[LeeM]

I'm having problems with the thermostat under the wheel arch that runs to the front oil cooler.
It never seems to open as the pipes don't get hot. I've replaced the stat with a second hand one but it's just the same.
Could it be a thermostat on the engine?
The car is an 85 3.2 Carrera.

[chrisbruck]

You sure the oil is getting hot enough to open the thermostat? If the ambient temp is below 60, I have to really go out of my way and hammer on my car hard to get it hot enough to open the thermostat. It's pretty rare for it ever to open in the winter, at least for me.

[MConn]

Check the oil lines near the jacking point, your lines may be crushed.

Fixed my Crushed Oil line for $5 and a beer.

Mike

[GH85Carrera]

If it is real cold the engine will never get up to "normal." I drove for 90 minutes in 0F temps and the oil temp never got above 160.

[KTL]

The thermostat on the engine sticking closed would cause high temperatures and that would force your external t-stat to open sooner. That little oil cooler on the engine is really effective because it's in pressure side of the oil circulation and it has a good source of air flow air blowing across it thanks to the ducting from the main engine fan. So if your oil temp isn't warming up enough, it's not a fault of the engine t-stat not working.

The external t-stat is in series with the engine t-stat because of it's location in the oil circulation. The the external t-stat sees oil after the oil has gone thru the engine & fallen to the bottom of the engine. The oil pump scavenges that "used" oil and sends it directly to the external t-stat, to either go thru the front oil cooler (t-stat open/flowing) or directly back to the oil tank/reservior (t-stat closed). So regardless of what is the status of the internal t-stat, the external t-stat always encounters the oil coming from the engine sump. Sure, if the oil is hotter in the sump as a result of the internal t-stat not opening, the external t-stat should open sooner. But the fact still remains that the external t-stat is receiving oil in the same fashion all the time.

Actually it's worth noting that the external t-stat functions in a way most people don't realize. The external t-stat has oil directed to the front oil cooler even when "closed." By "closed" I mean it doesn't allow oil to flow. The t-stat is closed on the return side. So oil is pushed to the cooler, but does not flow and therefore "backs up" by going thru a bypass port in order to for the oil to be returned to the oil tank w/out actually flowing thru the cooler. When the t-stat reaches 83C (180F), the temp regulator opens flow on the return side and allows oil to actually flow thru the cooler .

[pavegeno]

I had a bad external thermostat about 5 years ago. Replaced it and much better. About a year ago I started having temp problems again and thought I had the same issue going on. Turned out the internal thermostat was shot and now I'm back to normal...temps in the mid to high 80s in Hawaii and I rarely see 90C/194F even with my Griffith's a/c running and keeping me ice cold.

[schumicat]

you can replace just the plunger on the thermostat, around $40 part, mine failed in closed position. i tested it in boiling water and it was definitely bad. it is like the world's largest slotted screw to remove it, Tony (boyt911) made a special tool but I just used a big washer held w/ vise grips.

[Bob Kontak]

I have never had mine open up when only idling in the garage. Maybe on a blistering hot day and I did not check it but any time I try to do this, forget it. Nuttin'.

[Les Paul]

They make these for sockets.

[KTL]

That socket Les Paul pictured is often called a drag link socket. Why it's called that, I dunno.

In a pinch (because you don't have, or want to buy, a drag link socket) a suitable pipe wrench will get the cap off the thermostat.

[poorsha]

"In a pinch (because you don't have, or want to buy, a drag link socket) a suitable pipe wrench will get the cap off the thermostat."

Really struggling with mine.
Ordered a new cap as I know I will completely mess the original up (if I ever get it off).
Getting old. Losing strength

[KTL]

Big wrench ( I have a giant aluminum pipe wrench a friend gave me) is your friend, or slip a length of "cheater" pipe on your normal/small wrench. It'll come off. Gotta hold the t-stat in a good size benchtop vise, strongly secured to the bench. I've had a few that were real SOB mofos to get loose. Nice thing is, the pipe wrench grabs harder and harder the more torque you apply. So no worries about the wrench not holding!

[poorsha]

Trick is I am trying to do while still in car.
Perhaps I need to remove it

[KTL]

Originally Posted by poorsha

Trick is I am trying to do while still in car.
Perhaps I need to remove it

Yes you're likely going to break one of the oil line connections because it's very hard to support the t-stat in the wheel well

[Les Paul]

And good luck taking it off without galling the big nuts. They should have made it so it doesn't ruin your threads.

[schumicat]

that's how I did it. if you think that's hard trying attaching axles in a wal mart parking lot with no jack/stands. if you mess with the oil lines you probably will be buying a new thermostat housing as well.

Originally Posted by poorsha

Trick is I am trying to do while still in car.
Perhaps I need to remove it

i