Which Thermostat is Correct

[Thub]

So guys like the title suggests, what is the correct thermostat?

During tear down to verify everything is good in the cooling system I found that the thermostat that was in the car does not seem to match the new gates one I had ordered from Rock Auto. The new longer thermostat seems like it would be the correct one as it fits into the full water pump thermostat "body" and seals off the back of that housing with what seems like a smaller 2nd thermostat.

The car has always seemed to have a running warm/hot issue at idle or lower RPMs, romp on the throttle and it would drop 15-20 degrees...water pump impeller looked good, it appeared to plastic fins too so no vanishing impeller like on steel water pumps. I actually think it could have been a bad belt since the old one was pretty dry rotted and probably stretched out.

 

[FiveLeeter918]

It looks like someone cut the spring off or it broke and is floating through your system somewhere. The bottom is the correct design.

 

[E1]

Long one.

They'll both work but the short one gives erratic action.

I wanna say either Toyota or Nissan has a t-stat that makes a good substitute for the long one if you can't find the Ford one.

 

[SHOZ123]

The longer sealing disc is to close the thermostat bypass when the thermostat is fully open. It will cause overheating if there are other issues with the cooling system.

 

[gamefanatic]

You can get the Toyota one from Mishimoto, butit will run at 160°, which may be a bit cold in the winter...

 

[GEN 3 SHO FAN]

The longer sealing disc is to close the thermostat bypass when the thermostat is fully open. It will cause overheating if there are other issues with the cooling system.

Very interesting...
I tought the bypass (heads to t-stat) existing to give heat feedback to the t-stat and makes him opening and the t-stat "tail" was there to brake the speed at which the hot prestone comes to the t-stat and also slow down the cold prestone entering in the engine.

It's why I just cut the tail on mine (giving something similar to the shorter one), because at that time, I had heat problems. Running with this steup for some months now, I can say that there is no erratic actions. On contrary, the needle move a bit less because the t-stat react faster to heat changes (overall better flow of the prestone in the t-stat chamber). My feelling going into the same direction of Paul advice. (Your problem will be a little worse if you install the new t-stat.)

It's probably not the cause of your overheating problem tough.

A dirty or bad MAF can do such a thing.

If not already did, you can put more water in the prestone mix. It will help the cooling a little bit while you search the cause of the problem.