993 Thermostat Internals

[Green993]

I'm in the middle of a rebuild due to metal floating around in the oil system. I am replacing all the oil lines and using a new oil cooler. The tank has been overhauled at Pacific Cooler.

That leaves the t-stat. I have taken it apart and throroghly cleaned. Someone advised my that I should replace the internal mechanism as his failed after he did what I did. Here are my three option:

1. Use the cleaned up internal pieces as is.

2. Replace internals with a good used one I have with 51K on it (i have on hand).

3. Buy new internals and use them (very expensive).

Leaning towards number 2. How do these fail?

[KTL]

If you've already got it ALL apart and all you need to replace is the mechanism, which is the internal temperature regulator piece, I think you should just replace the regulator. It's only $39, which is really cheap in my mind. I'm not seeing what pieces are expensive. Even the regulator cover piece, which is usually a pain to remove & you have to drill & tap a hole in it to put a bolt in it for use as a pull point, is only $39.

Everything else looks to be clean-able and replaced as is, based on what I can see from the parts diagram. I've only worked with the older 964 and pre-1989 t-stats thus far. So i'm not personally familiar with the inner workings of the 993 t-stat.

The only failure mode these suffer is they stop regulating the temperature properly. Meaning, either they stay closed and the engine runs hot (oil cooler not seeing oil flow) or always stay open. You know it when its stuck closed because you'll see the temperature go way up on the gauge. Stuck open you don't really notice because temperatures are always fine.

[Green993]

Good advice. I am going to replace the springs, regulator and o-ring. Re-use the lid and clip.