Thermostat question

Joined
Feb 2, 2019
Messages
65
Location
Austin
So I have begun replacing parts on my cooling system starting with the radiator and all of the radiator hoses. Today I decided to take apart the thermostat housing, and to my surprise there is no thermostat. I have had no issues with my engine running cool, it typically holds 180* on long drives and 160* on my short commute.

That being said, why would the PO remove this, and what do I do now?
 
Joined
Feb 2, 2019
Messages
65
Location
Austin
My guess is the PO took out the thermostat because the radiator was broken, and caused overheating. thermostat removed = engine runs at lower temps. This could also explain my temp gauge that barely moves (lower temps).

What can/should I do to make sure this hasn't caused any issues?
 

Steamer

SILVER Star
 
Joined
Jul 20, 2009
Messages
971
Location
Miami, FL
You should use a thermostat. The F & 2F thermostat just doesn’t simply open and close like some other vehicles. It also controls the bypass function of the cooling system. When the engine is cold the thermostat is closed to the engine but also open to the bypass, so the water just re-circulates without going through the engine. Hence, a quicker engine warm up. When the engine warms and calls for cooling, the thermostat opens and closes off the bypass.

With the thermostat missing, the bypass is always open, and you’ll never get all the water circulating through the engine because a portion of it will bypass through the open port. The bypass is the small short hose that goes from the thermostat housing to the water pump.

When you get a thermostat, and you should, put it in a pot of water on the stove to make it open and observe the function. It’ll all come clear. And when you install it, you’ll need two gaskets. One between the two halves of the housing. And then the ring gasket that goes on top of the thermostat.

Feel lucky that you got the t-stat housing apart. Steel bolts in the aluminum housing are prone to seize up and often strip for snap off. Anti- seize compound or grease is recommended.
 
Joined
Feb 2, 2019
Messages
65
Location
Austin
You should use a thermostat. The F & 2F thermostat just doesn’t simply open and close like some other vehicles. It also controls the bypass function of the cooling system. When the engine is cold the thermostat is closed to the engine but also open to the bypass, so the water just re-circulates without going through the engine. Hence, a quicker engine warm up. When the engine warms and calls for cooling, the thermostat opens and closes off the bypass.

With the thermostat missing, the bypass is always open, and you’ll never get all the water circulating through the engine because a portion of it will bypass through the open port. The bypass is the small short hose that goes from the thermostat housing to the water pump.

When you get a thermostat, and you should, put it in a pot of water on the stove to make it open and observe the function. It’ll all come clear. And when you install it, you’ll need two gaskets. One between the two halves of the housing. And then the ring gasket that goes on top of the thermostat.

Feel lucky that you got the t-stat housing apart. Steel bolts in the aluminum housing are prone to seize up and often strip for snap off. Anti- seize compound or grease is recommended.
Thank you for the response! I will be ordering a thermostat today.
 
Joined
Feb 5, 2019
Messages
225
Location
Bay Area California
Can someone take a pic of where the thermstat is located I need to check and see if it’s stuck open or closed or something - car won’t stay running and I’ve rebuild carb and check solenoid etc
 

Steamer

SILVER Star
 
Joined
Jul 20, 2009
Messages
971
Location
Miami, FL
It’s bolted to the front end of the head with two horizontal bolts. The housing is cast aluminum, in two pieces, and the top half comes off to change the thermostat. The top part has two or three hoses connected to it. The big hose that goes to top of the radiator is connected to the driver’s side of the top half. The smaller by-pass hose is on the passenger’s side of it. And goes from the top half, down to the water pump. Different years are a bit different. My 74 has two bolts holding on the top half and later years have four bolts. My 83-FJ60 top half has the four bolts and an additional outlet the passenger’s side aiming upward for an oil cooler.

If you plan to open it up, I would have gaskets ready on hand. There’s two. One is a ring gasket for the top of the T-stat and one that goes between the two halves. Also be prepared for frozen or stuck bolts that hold the two halves together. It’s common for corrosion to freeze them up because of the dissimilar metals. It would be good to soak the bolts with penetrating oil days ahead of time. Apply it often and the longer the better. There are numerous threads on stripped thermostat housing bolts. New housings are available should it get destroyed.
 
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