Oil thermostat has failed: questions on procedures

[MarkRobinson]

I've read that most all people who have failed thermostats have "replaced" them in lieu of repair them: as they're described as a "stack of quarters" with a spring, I'm not sure if it's not dirt/age that causes t-stats to fail. Ideas??

Our t-stat failed in '98 after we purchased the car, now it's out again & have questions about the thermostat (clean or replace?), the spring (clean or replace?) and a sealing o-ring (replace of course).

Thanks!

Mark

[lucittm]

I thought they were pretty reliable with only one moving part. Was your oil particularly dirty? Did the car overheat before the thermostat failed?

Just wondering.

Mark

[911nut]

I overhauled mine when I replaced the oil lines. It's a big, messy but rewarding job.
First, clean the area around the thermostat and oil tank completely with brake cleaner and rags; I mean clean enough to eat off of. If you get any dirt into the thermostat or oil tank, you will need to remove the thermostat from the hard lines running out to the oil cooler which can get ugly fast if you have to cut the nuts off of the lines. The oil tank will require removal and cleaning too (ask me how I know).
Then, there's a circlip that holds the cover on. Remove it.
Next, the cover should pop out, unless bi-metallic corrosion is holding it in the body. In that case you will need to drill and tap a hole in the center of the cover and use a slide hammer to remove it (you can then buy a new cover (964-207-351-01) or tig up the hole in the old cover and re-use, saving $30).
The guts of the thermostat will be accessible. There's an o-ring (999-701-393-40) around the thermostat insert that should be replaced. Since your thermostat is bad, you will need to get another insert and spring (964-207-349-02). Clean and inspect the body real good and re-assemble if there are no scratches of burrs in the thermostat bore.
I recommend replacing all the oil lines running into the thermostat at this time as there will be a few weepers.

[MarkRobinson]

Thanks Paul,

I'll replace my lines when I transplant my t3.6 engine in a month or so: just want to get the t-stat fixed first.

If it's an insert & spring, what "fails"? the spring?? Insert gets lodged? Just curious.
Thanks for the write up: great people, great forum.

Mark

Here's a picture of my car at a Ferrari-Lambo-Porsche breakfast on Saturday.

[911nut]

Originally Posted by MarkRobinson

If it's an insert & spring, what "fails"? the spring?? Insert gets lodged? Just curious.
Thanks for the write up: great people, great forum.

Here's a picture of my car at a Ferrari-Lambo-Porsche breakfast on Saturday.

Pretty car.
If the 964 thermostat is like most other thermostats there's a capsule of paraffin wax that, when it melts, moves a piston that allows oil to flow to the front cooler. When the wax becomes contaminated the melting point is raised and the piston won't move.
A new insert and spring costs $133 from our host. I can't find a troubleshooting procedure for the insert but if you are sure that the insert is bad, you will have to spend the money.

[MarkRobinson]

Thanks Paul: I like knowing "why".

Mark

[911jettat]

Here are a couple pictures from a N.A. C2...

more pictures here: Picasa Web Albums - Udo - thermo-sil

[MarkRobinson]

excellent: that's what I had envisioned.

Mark.

[Montreal911]

reviving an old thread... can I simply remove the thermostat insert (PN 96420734902) and allow the engine to run cooler?

https://www.pelicanparts.com/More_Info/96420734902.htm?pn=964-207-349-02-OEM&bc=c

[Montreal911]

some say that you need the thermostat because oil needs to be above a certain temperature before sending it to the front cooler or you risk blowing out the oil cooler with too much pressure from thick oil. any comments?

[mepstein]

I don’t have a thermostat on my 914-3.2 conversion. I was told by a well known race car builder that I would be good above 50 degrees. Basically start out in the garage if it’s cold out.