1995 Buick Skylark - 2.4L Overheat @ Idle

[Holly]

Over heating problem when at idle.

Cooling fan runs. Replaced radiator. Changed thermostat 2 times. Put air pressure in cylinders, no leak and no bubbles in overflow tank. New upper hose connector on end of head. Took aluminum housing off of water pump, checked impeller - tight and looks as good as new. Upper radiator hose and radiator are cold, but boiling in overflow. Does not lose any heat. Temp running okay driving but as soon as slow down, temp goes to hot and boiling in overflow. Fan is running.

[liljoe]

Check the little bypass hose/pipe that goes from water outlet to reservoir to make sure it is not stopped up, also make sure the heater core is flowing good. Have seen both of these cause this problem on this engine.

[fortknoxx]

has it been burped?

[steven kiser]

driving around it's ok but at an idle it overheats. i have a high volume fan i use to blow air through a radiator when i use the dyno. i'll use that to force air through in these situations. the fan may be a two speed and you've lost the second or it may be a circulation issue. i'm thinking circulation because of the way the hoses are hot and cold. i didn't see anything about a t/stat.

[Holly]

Thanks, Liljoe......Must have been a partially plugged heater core! Backflushed both ways and refilled using airlift!!!

[liljoe]

Had one of these run me nuts, turns out the coolant flow for the heater core also flows past the back side of the tstat and that is how it is exposed to engine heat. If h-core is plugged the t-stat will not get enough hot water flowing across it to open up. Glad that I was able to help..

one point for the Green team

[Jeff @ Able Auto]

Thanks for posting the fix. Great job everyone!