Coolant leaking in overflow valve [Archive] - Forum


View Full Version : Coolant leaking in overflow valve

08-17-2009, 08:58 AM
I recently took my car to get worked on because it lost a lot of coolant while i was parking after a 15 min drive around town, the coolant leaked out all over the passanger side engine bay. I got the car back and they replaced a radiator cap and that was coolant is leaking out of the overflow valve as soon as you start the car. I just dropped the car off at a mechanic, but do any of you know what could be wrong...Could they have installed a wrong cap on the radiator, could the water pump be bad? Ideas?

Mike Jung
08-17-2009, 09:04 AM
What temperature are you showing at the engine coolant temperature gauge ?

08-17-2009, 02:13 PM
if your engine is running fairly hot it could be water pump but then coolant wouldnt be moving at all so it would have to boil out. it would be a stuck thermostat. i had this problem with an old chevy v8 were it would boil out into the overflow. but if your not overheating then i have no idea

08-18-2009, 11:31 AM
The valve starts spitting fluid as soon as the car starts...the shop i took it to just told me it was some kind of "body controle module" (have no clue what the full part name is). They said this part is messed up and thats causing the fans not to kick on when you start the car which is causing coolant to leak into the overflow somehow. But i thought the fans dont kick on anyways until the engine gets hotter than normal driving temp??? Does this sound right or are they replacing a part that dosnt need replacing?

08-18-2009, 05:37 PM
im guessen when they say body control module they mean pcm... and that would deal with that fans but the fans only kick on once the coolant reaches a ceartain temp. and you can buy a tuned pcm from mp racing and put it in yourself for a whole lot less then what a shop will charge you for a stock pcm.

The coolant leak issue i have no idea, i might if i actually saw it leaking but ive never had this problem or heard of it myself... nor does it make any sense, theres a total of 4 hoses on the reservoir:

The overflow at the top near the cap its the smallest and should just bend straight down., theres 2 on the top middle of the reservoir, one of them goes to a metal line that comes out from the water neck that goes to the thermo, the other goes to the radiator which i beleave is an overflow hose for the radiator. then the bigger hose at the bottom also goes to the radiator which is used for filling it...

the only way for coolant to be spraying out would be pressure is built up from it overheating and boiling.

Personally i would take it to GM and have them look at it to make sure its done right i dont trust small shops

08-19-2009, 12:05 AM
Just an idea but possibly a bad head gasket blowing pressure through the cooling system?

Anyways whoever your mechanic is he doesn't sound like he knows what he's doing.

08-19-2009, 09:55 PM
hmmm never really thought of that... ask them to do a compression test.

08-20-2009, 07:32 AM