I am having an issue with my overflow filling/blowing steam once the engine warms up. The temp gauge seems alright while this is happening, but I have read many things on this forum about the stock coolant temperature gauge being highly inaccurate. I still have the ast, thermostat is opening as the radiator gets plenty hot. I also removed it and had the same issue. Anyone have any insight on this issue?

Thanks!!!

 

Could be a bad coolant seal pressurizing the cooling system.

 

I was afraid of that. A bad seal can do that similar to a blown head gasket?

 

Best case scenario is the overflow is overfilled or you have a pinhole leak in the system that isn't allowing vacuum to draw coolant back into the motor. Worst case scenario you have a blow coolant seal which is like a bad head gasket. I would start here https://www.rx7club.com/3rd-generati...thread-571088/
Removing the thermostat will actually allow a portion of coolant to bypass the radiator and cause the car to run hotter.

 

Great read and greatly appreciated! I do not have an ast pressure relief... Do you think that this may be the cause of air in the system like suggested? to me it seems like the system is just open without a cap without this device...

 

have you tried removing the radiator cap when it is warming up to see if it has a lot of bubbles?

 

It was what I said in the previous post, the AST is incomplete without that relief valve. I put a cap setup from an earlier generation with the overflow relief as part of the cap assembly and plugged the other hole so it could utilize the spring style cap relief system and it works fine now.