Loosing coolant somewhere...please help

**tgarison** · 05-29-2011

Hey forum,

I have noticed a constant problem with my 99 Grand Prix Gt 177,6XX miles on it ever since i did a coolant flush and change. B.T.W. I am running with Advanced Auto Parts brand dexcool in it if that matters any. About every 2 weeks or so the Low Coolant light comes on. I have checked for leaks at the elbows...no leak there, i looked under the car while its running...nothing dripping, it was leaking at the thermostat housing but i fixed that with some southern engineering. I haven't done a compression check to test the head gasket because those almost never let go, the oil looks fine no milkshake just dirty, I checked the UIM best i could and didn't see anything out of the ordinary. The car isn't overheating even in the triple digit texas summer heat. Quiet frankly i'm at my wits end with were its leaking at. I will check the UIM tommorow again to make sure. Any help you guys can offer will be much appreciated.

Thanks in advance

**Fivefingerdeathpunch** · 05-29-2011

I betcha its slowly eating the coolant through the LIM gasket.

**Scottydoggs** · 05-29-2011

pressure test the cooling system.

**jamar22** · 06-08-2011

I agree with five finger my car did the same thing then all of a sudden i got the milkshake effect so when i was breaking down my motor it ended up being the lim gaskets..you can loose fluid internally in the upper and lower intakes if the gaskets are gonna go soon hope this helps...

**05GTPcmpg** · 06-08-2011

yeah I agree its most definately lim gasket, If its leaking externally look at the transmission from the hood, if you see stains on the top of the transmission thats where it would leak almost all the time. IF not its internal either way it needs to be replaced with the 2nd design lim gasket which is available at Advance for 44 bucks

**Dragon1972** · 06-28-2011

Sometimes the lim shows external leaking but more than like ly it is leaking from the O-rings for the throttle body, either way the only fix is a new uim and gasket set. The plastic uim warps and twists allowing the coolant to pass by these o-rings filling the lim with coolant, eventually getting to the point of hydro-locking your engine. Go through and replace the plenum (Dorman) and gaskets(Felpro) and change oil and filter and you'll be good.

**BillBoost37** · 06-28-2011

Originally Posted by Dragon1972

Sometimes the lim shows external leaking but more than like ly it is leaking from the O-rings for the throttle body, either way the only fix is a new uim and gasket set. The plastic uim warps and twists allowing the coolant to pass by these o-rings filling the lim with coolant, eventually getting to the point of hydro-locking your engine. Go through and replace the plenum (Dorman) and gaskets(Felpro) and change oil and filter and you'll be good.

Yes the o-rings can leak, but 99% of the time the egr tube has heat cycled the UIM enough to crack it in the EGR hole area. This allows the coolant going through it to fill the intake. The way to tell if it's the o-rings vs the EGR area is if the intake is wet inside. The O-rings would leak down into the LIM. In the end though..a leak is a leak.

Common external leaks are on top of the LIM. At the throttle body, under the throttle body at the little cover on the LIM for the coolant turn around, coolant elbows. Other common things are unsealed LIM bolts.

**tgarison** · 09-16-2011

Hey forum,

Thought I would give all of you a status update on the coolant leak...its fixed.

Turns out the radiator had a small leak behind the radiator fans and the radiator cap wasn't holding pressure allowing the coolant to evaporate. I flushed the system, replaced the radiator and radiator cap, filled it with the universal antifreeze (yellowish looking stuff) and it hasn't leaked a drop since.

Thanks for all your help and idea's
tgarison

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