Mystery Coolant Leak

[Gems]

2001 LS with the 3.8L motor... For the past few months the Coolant Level warning light turns on and off, sometimes stays on all the time after driving for about 15 minutes... I open the radiator cap and see the coolant level about 1 inch below the top, so I top it off... I've been doing this about every 3 weeks for the past few months... I've used up 1 gallon of 50/50 mix over these past few months...Finally today I bring it to the dealer and he does a pressure test and cannot find any leaks... He leaves the system pressurized for over an hour with no change in pressure... The dealer also tells me he fully heated up the engine and did a pressure test again and cannot detect a leak anywhere... Any ideas??

[1996Chreokee]

do you smell it coming out the tail pipe? have you pulled the sparklers (Spark plugs) and checked their condition? thats a tooooooooooooooooooon of coolant to be down... i had the same problem.... THought it was the intake ( the mechanic ) and it ended up being just the top radiator hose loose... My temp gauge kept moving around alot too...

[maxwedge]

Upper intake failure is common at the egr passages, to a lesser extent lower int. gaskets, the throttle body should be removed to check the egr passage in the upper intake. This assumes no external leaks of course.

[Gems]

Originally Posted by maxwedge

Upper intake failure is common at the egr passages, to a lesser extent lower int. gaskets, the throttle body should be removed to check the egr passage in the upper intake. This assumes no external leaks of course.

If I am to believe the dealer, the UIM gasket was changed about 7 months ago... Are the EGR passages part of that gasket??... There are no visible external leaks...

[maxwedge]

The upper intake seals usually do not go bad, the plastic manifold does, you would think because this is a common problem they would look at the egr passages, that is all I can say.

[Gems]

Originally Posted by maxwedge

The upper intake seals usually do not go bad, the plastic manifold does, you would think because this is a common problem they would look at the egr passages, that is all I can say.

I checked my receipts from the Chevy dealer and the last receipt from May says they replaced the UIM gaskets... It's referred to as a UIM gasket kit and they changed it under my GMPP warranty... Today the low coolant warning light never came on, even after about 40 miles of driving... Go figure...

[Gems]

A few days after this last post the low coolant light started turning on and off again... Up to now I've always added coolant directly into the radiator... This time I added coolant into the overflow tank, maybe about 1 quart or less... Since then the low coolant light has not turned back on and it's been about a week so far... I am confused now... What's the difference between adding coolant into the overflow tank versus the radiator?

[maxwedge]

None.

[16th hippy]

doesn't the overflow tank have the low coolant sensor on the 01's...can't remember when they switched all that around.

[Gems]

On the 3.8L motor that I have the level sensor is on the back of the radiator, below the filler neck, about 4 inches down... On the 3.4L engine, I believe it is in the overflow tank...

[j cAT]

Originally Posted by Gems

On the 3.8L motor that I have the level sensor is on the back of the radiator, below the filler neck, about 4 inches down... On the 3.4L engine, I believe it is in the overflow tank...

I would go to another dealer to have the leak found . you are using tooo much coolant. tell them to use dye to find leak . pressure testing may not work especially if head gasket..........pull plugs if a plug is white you have bad head and /or head gasket..intake manifolds are a known problem for cracking on GM vehicles of this vintage..........

[maxwedge]

Correct, as I have been saying the upper intake passages at the egr and again, to a lesser extent, the lower gaskets, this all repeats what has been suggested.

[Colt Hero]

For the record, the Coolant Level Sensor is on the radiator just below the filler neck opening on the 3.4 engine. I have a 2002 Impala and I've pulled this sensor twice now to clean it off. It gets gunked up and gives a false reading. I'm pretty certain this is caused by the infamous intake leak which I'm all but certain my engine has, but I haven't fixed it yet. Currently, the illuminated message has been ON for about a month straight now, whereas before it would come and go. Maybe this means the leak has gotten worse, although the fluid level loss still seems to be fairly low and consistent, and the oil always looks OK (visually at least) when I change it every 3k miles. Maybe I should send one of the 5 quarts I've captured now over the last year to some chemical analysis outfit to see if there's any glycol in there...

[1996Chreokee]

A buddy of mine who was a gm tech for 10 years said he finds that the dexcol doesn't show up good in the oil for some reason. He said its also more difficult to see and external leak too. But you don't wanna let that leaky intake go for to long because it can cause some major problems