2003 Pontiac Grand Prix OVERHEATING

Asked by Sep 27, 2017 at 09:47 PM about the Pontiac Grand Prix

Question type: Maintenance & Repair

I have a 03 Pontiac Grand Prix GT that I
bought from a guy a cpl years ago. Started
to have overheating problems....took it to a
shop they flushed my cooling system n told
me some idiot who owned the car b4 me
filled the radiator with Stopleak. So long
story short for 3 yrs I constantly was
flushing my cooling system to get all the
brown gunk outta my cooling system. So
about 1 1/2 yrs ago I replaced my radiator
water pump timing belt at same said shop.
Just recently my car started overheating
really bad no white smoke but smell of
burning coolant in the cab bogged down
accelerstion, heat coming through the floor
vents etc. So I replaced the head gaskets,
radiator cap,stretch bolts, replace coolant,
bleed air outta system & had machine shop
machine the heads and check for cracks
chips all came back good. All was well for a
cpl days n now it's overheating fairly quick
after cold start and leaking coolant....so I
need HELP PLEASE!!!!

16 Answers

8,860

Possibly small crevices in the engine that are supposed to funnel coolant could still be clogged with stop leak. Did you replace the thermostat? I did not see this on your list. Coolant temperature sensor...is this original? Have you pressure tested system to make sure it is holding pressure?

Yes replaced therm

Yes replaced thermistat the only thing I can think of any more is cracked water pump or clog in the system sum where

8,860

Pressure test and go from there

8,860

Are the fans running?

8,860

You may be right in that there might be something wrong with the water pump. Impeller not turning?

8,860

Was the thermostat installed correctly? Not only the correct way of flow but upside down will not let the system bleed on some models. Does yours have a small hole on the rim? If so this needs to be installed in the 12 o'clock position.

8,860

Fan relay or fuse blown.

8,860

Check engine light on for coolant temperature sensor circuit that might uncover wiring issue.

8,860

Is your leak a visible leak or using so you don't know where it is going?

Correct I'm not sure if the impellers not turning or if there's a crack in the water pump..no check engine light. Well small puddle but no visible leak while cars sitting idle

Yes fans are kicking on a about 1/2 temp

Yes therm installed correctly

8,860

That small leak is enough for it to overheat. It is not holding pressure with a leak.

So what's my next steps?

8,860

If you are not exactly sure where the leak is, I would pressure test so you can see the leak. (Might not leak until it is under pressure). Then fix it so it holds the right amount of pounds that your system is designed to hold. (Generally 13 - 18 lbs). Your cap will sometimes have this number. If not test at 13 lbs. if you do not see a leak and you are losing pressure, test the cap and if it passes, you have an internal leak. Generally head gasket.

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