External Thermostat Testing

[2jmotorsports]

Hello Pelicans,

I am currently rebuilding my external thermostat and wanted to run my test results by you.

1. Drop it in a pot of water. Notice the circular plunger is flush with the cylindrical end of the thermostat unit.



2. Bring it up to a boil.



3. Plunger goes up about .400 inches. Does this look like acceptable travel?



4. If you drop it in the housing, the plunger holds the unit up and exposes the slots through the port shown here. I am guessing in this condition oil is allowed to pass through the lines and front cooler.



Lastly the plunger stayed up after the unit cooled. I was able to push it back down with finger pressure. My guess is in the housing, while hot, the plunger will overcome the spring pressure to raise the unit, but once it cools down, the spring pressure will push the plunger back into the unit, lowering the unit and covering the slots, and prevent oil flow through the front cooler until the temp goes back up again.

So what do you guys think? Is this unit still good?

Thanks in advance.

[86 911 Targa]

What prompted the re-build?

Gerry

[manbridge 74]

Been awhile since I pan tested one. How did it operate on the car? I like to use a infared gun to read temps.

One thing I recall doing on one that I noticed was sticking was polishing the plunger and bore where I saw some scuffing. No sticking on re-test. Not sure if yours is designed to come apart though. I seem to recall mine having a large circlip.

[2jmotorsports]

Originally Posted by 86 911 Targa

What prompted the re-build?

Gerry

Wrapping up a rebuild on a tired engine and rebuilding the oil cooling system to clean everything out.

Thermostat worked fine beforehand. Just testing as a sanity check while Im in there.

[T77911S]

don't know the cost but why not just replace it and not worry.

any problems getting the hoses off the Tstat.

[2jmotorsports]

Originally Posted by T77911S

don't know the cost but why not just replace it and not worry.

any problems getting the hoses off the Tstat.

They are only about $30. If I bought a new one I would probably test it anyway to verify it is not a dud. Problem is no acceptable criteria are listed anywhere.

Thankfully no issues removing the hoses. Removed all the lines as a unit, lots of penetrating oil, heat, and wrench clearance to get them off with no damage to either the tstat housing or the lines.