Sticking Thermostat -- 1972 911

[Jack Olsen]

1972 911 with front oil coolers. My symptom is intermittent failure of the thermostat – I’ll see temps climb in normal driving to 240°, with 10 minutes or so passing before it comes back down and functions normally with my front oil coolers. Most of the time, the thermostat works perfectly. But I’ve had three incidents of it sticking in the past handful of drives.

I was never the brightest bulb on the Christmas tree, so feel free to explain it to me like I’m five. Here are my questions:

1) First, let me confirm that there’s no way to do this ‘in situ.’ (I'm sure that'd be stupid, but a lazy guy can dream right?)

2) I believe I have the 1972 filter housing that’s been machined to accept a standard 911 thermostat (the 1972T-to1972S conversion of the filter console). So I believe the part for a replacement thermostat would be 930-107-765-00, which is the same part used as the thermostat in the engine itself. But I’m not certain if another path was followed in putting mine together. I'll check that, but it would be helpful to know if mine is clearly NOT that.

3) My plan is to remove the three lines in the back, then unfasten and slide out the oil filter console. Then I'll open it up, clean things out, and (maybe? probably?) replace the thermostat itself. I believe the easiest way to get the thing disconnected is going at A, B and D in the diagram below. But maybe C. Am I looking at this wrong?

4) From the looks of things, I don’t see any parts I need – except possibly #14 in the diagram below. Is that an aluminum crush washer? Could I heat up the existing one to 500° for an hour to re-soften it?

5) Any special tools needed? I think this thermostat does NOT have the coin slot for removal. But I don’t have a very clear look at it, yet. (Wait, I got a shot.)

6) Should I test the thermostat once I’ve got it apart? Is there any advantage to retaining the original part (in terms of quality control, etc) over a new one?

[rowingone]

Absolutely test the thermostat after you remove it. Use a heat gun and make sure it opens at the right temperature. Youtube has video on how to test the thermostat.

[rowingone]

https://www.youtube.com/watch?v=DWDsVb5t_k8&t=2s

[47silver]

Use a pot of water or vegetable oil heat to 180. Should see it begin to move

[rdimarco]

I've had thermostats that tested good in boiling water, but still incompletely opened when in use. You can replace just the thermostat insert. I've had good luck with the Mahle/Behr inserts in engine and the external thermostat.