engine temp fluxuation

[snoopybear]

I just had a cooling system flush on my 1991 Bravada. I believe I have an airlock that I can't get out of the system.

The problem shows up in the operating temperature that fluxuates from 150 to all the way hot. I've checked the thermostat, rad, rad cap, and pump. I've tried parking it on an incline and running the engine with the cap off. The only way I can get it to cool off is to either remove the thermostat or put a hole in the thermostat flange. When I run it with a hole in the thermostat, it won't get over 125 degrees. I've almost ruled out a head gasket in that there are very few bubbles showing in the coolant and the oil doesn't get milky.

Any help with a diagnosis or with dealing with that possible airlock, will be appreciated.

[ricksza]

Try removing the thermostat and fill the block from there, reinstall the thermostat and upper radiator hose, then fill the radiator the rest of the way. that will help with an air pocket in the block.

[BlazerLT]

Originally Posted by snoopybear

I just had a cooling system flush on my 1991 Bravada. I believe I have an airlock that I can't get out of the system.

The problem shows up in the operating temperature that fluxuates from 150 to all the way hot. I've checked the thermostat, rad, rad cap, and pump. I've tried parking it on an incline and running the engine with the cap off. The only way I can get it to cool off is to either remove the thermostat or put a hole in the thermostat flange. When I run it with a hole in the thermostat, it won't get over 125 degrees. I've almost ruled out a head gasket in that there are very few bubbles showing in the coolant and the oil doesn't get milky.

Any help with a diagnosis or with dealing with that possible airlock, will be appreciated.

I would highly recommend you replace the rad cap and thermostat instead of checking it.

A rad cap not sealing could loose pressure and drop the boiling point considerably.