I'm having a problem with my thermostat not opening when I crank my car up and warm it up. It will overheat if I let it and I've confirmed by feeling the upper hose that it's not opening. Weird part is if you cut it off for five minutes, it opens and will run fine at around 180 degrees. I've bought two thermostats and taken one out of my truck that I know is good. They all do the same thing. My car is an 86 Camaro with a carbed stock 350. Thanks in advance for your help.

 

Do you have a mechanical fan or electric fan(s)?

 

Electric. It's not that though. It's the thermostat not opening. The upper radiator hose stays cold until you cut the car off for a few minutes. Then crank it back up and it opens and runs at180 after that.

 

Do you have an air bubble in the system?

 

What makes you think it will overheat? And what degree temp are the thermostats you're using?

 

After replacing the thermostat, what's your refill procedure?

1. Engine cold, open the radiator cap and add coolant until full.

2. Leave the cap off and start the engine. The coolant level may fall.

3. Continue to top off coolant until the thermostat opens; carefully look into the radiator neck. When the thermostat opens, you'll see coolant flowing out of the tubes into the side tank. The flow should be substantial, not a trickle.

4. Top off coolant after the thermostat closes.

5. Repeat 3. & 4. allowing the thermostat to open and close a few times. This should be more than enough to purge the air out of the system.

6. Install the cap.

7. Top off the overflow tank.

8. Shut off the engine.

 

Either you have defective thermostats..you can check by boiling water in a pot and checking them that way...or you have an air bubble as mentioned previously and you need to burp the motor.

 

a small hole, drilled into the side of the t-stat will prevent air bubbles from forming and alleviate any concern as to proper fill procedures.

 

i agree about drilling a small hole. i usually drill 3 small 1/8" holes around the edge.
you might have some plugged up coolant passages? try a good flush of the coolant system, and next time you have the t-stat out, try feeding some weedeater line into the coolant passages to see if theres any built up crud in there.

 

Hopefully you looked at this... is the t-stat in the correct way? Sounds as though it is upside down. That would allow it to open after it becomes heat soaked. Sounds silly - it has happened before - don't ask how I know. Byron

 

Thanks for all the responses. I've been sick for most of the week. I took the thermostat out today and drilled a 1/8" hole in the side. It is doing slightly better. Thanks for all the help!