heat gauge rises,, hot air not coming through vents?

[50John]

I have a 93 cobra with a S trim blower and a snow performance boost cooler. The radiator is by Fluidyne. I would like some advice as to why at times under normal driving conditions I see my radiatior begin to climb high on the gauge all of the sudden. I then go to turn on the heater full blast to assist with the problem at which time cold air is blowing through the vents. Approx 10-15 seconds later the heat suddenly kicks through and the gauge drops down to normal and all is well... however I later check under the hood and see that some coolant has been spewed out onto the battery from the over flow bottle. Is this a thermostat problem? any suggestions-help would be appreciated. 50John

 

[Chris_Red_V8]

I'd start the car and check the radiator cap for bubbling, could be signs a headgasket let go.

 

[BlownFiveLiter]

Sounds like air pockets in your cooling system. The coolant expands, you get a momentary blast of heat when some coolant goes into the heater core, but it quickly cools back down. Meanwhile, you're boiling coolant in the engine because of the air pockets, and spewing it on the battery. Put the front end pretty high up on some jackstands so the radiator is the high point in the system and fill it back up.

 

[mousetrap82]

sounds to me like it is the thermostat. that would explain why the heater would finally start working and why the gauges would finally look good. the thermostat is probably not opening at the correct temp