I plan to fix this with a Subaru thermostat soon, but I'm curious about the technical details...

 

We had an aftermarket thermostat put in at a timing belt change. Now the temp. gauge runs up to a hotter point than I ever recall before, but it eventually settles down to where it usually runs. It never seems dangerously hot, but hotter than before.

 

Does this mean the thermostat is sticking open or sticking shut? (Or, of course, neither... )

If its getting hot, and then settling down as you say, then it may be sticking closed for a short period.

 

I had one that was stuck OPEN.... and all that does is make your car never fully warm up (in winter)

engine, transmission, mileage?

Dave we do not know what car/engine you are talking about

but

some aftermarket T-stats will fit in upside down.

 

This may cause what you describe, esp in an EJ engine

with the T-stat on the block side of the lower hose.

 

 

"Coils to the block so it won't get too hot"

 

 

 

You are doing the right thing getting an OEM T-stat

See Porc73's pictures of the difference.

My car is doing the same thing. I really need to get around to doing some stuff. I have a Napa thermostat! Subaru + NON OEM parts = Alot of head aches and more money in the long run.

It has been proposed that a blocked or restricted heater core could cause these kinds of issues.

 

The longer Subaru OEM thermostat places the element nicely in the flow coming back to the water pump suction from the heater core and throttle coolant bypass circuits.

 

A few years ago, I tested OEM and aftermarket side by side and, IIRC, the aftermarket one had a smaller opening, opened later, stayed open for a shorter time. And was, as the above photo shows, flimsier.

Sorry, I forgot to post the car specs. It's an '03 Outback, standard 4 cyl. auto trans. with 95000 miles on it.

 

I'll post back if the Soob one fixes the problem.

After seeing Porcupine's most excellent pictures.

 

I had to see if it is true that a

junk aftermarket T-stat

will fit in upside down.

 

I had the parts on the bench so I took a look

 

Fit fine, but will NOT last a long time

 

Looking at those last photos, the "jiggle pin" is also mounted incorrectly by the thermostat manufacturer.

 

(Even though that way round seems right to me, can't understand why Subaru put the pin the other way round. Still, Subaru engineers most often seem to know what they're doing, so there must be a good reason!)

Isn't that little vent on the rim of the OEM stat (the above mention jiggle pin) to help in purging any air in the system? The after markets don't have that. Soobs are hard enough to vent with the OEM stats. I would think some of the problems with the after markets are due to air pockets.

both have jiggle pins

and you are correct on their purpose

 

I believe what Setright refers to is

the aftermarket t stat pin

 

closes when mounted in a EJ series engine.

 

This due no doubt to the upside down

mounting.

 

Very astute observation I must say.