Coolant problem- Dex-Cool with 99 Buick Century

-We have a 99 Buick with 38,000 miles. At 30,000 miles the car overheated and we had to find a mechanic in unfamiliar area. He told us car was unsafe to drive unless we had new radiator system installed (water pump, radiator flush, pressure test, radiator system flush, radiator kit (premium), anti-freeze - 2 gallons, lower and upper radiator hoses) at a cost of almost $1200.

FYI the car is in Florida full time - under cover.

Recently the “low coolant” signal has come on and after checking with a local mechanic, he said the manifold gasket was leaking and it could be fixed for about $600. We are reluctant to spend that money unless we can feel somewhat certain that the main problem is solved. We understand that at some point there was a class action suit against GM because of problems with Dex-Cool which is the required coolant for GM cars. In the meantime, we have been adding
plain water to the reserve tank but are very concerned that this may cause additional damage. There is never any leakage under the car.

HELP would be appreciated ASAP.

Running water causes corrosion and decreases the boiling point and increases the freezing point. The first guy was making his boat payment. The second mechanic was more than likely correct. A system pressure test will likely show you are losing pressure. A check of the radiator when the car is running will likely show gas bubbles. If you are loosing it in the cylinder head due to a bad gasket a leak down test should prove it.

Repair jobs like this are about the norm for a 14-15 year old car.
Shop around for a good mechanic and have the car checked over at least once a year
to avoid problems on the road.
Try the “Mechanics Files” button at the top of this page.

I think the mechanic on the road padded the bill a bit.
Were the water pump AND the hoses leaking and about to fail?
The flushes probably weren’t essential to getting you back on the road.

The leaking manifold gasket allows coolant to get drawn through the engine and out the tailpipe.
There won’t be any drips.
I would get the manifold fixed, the dex-cool removed and replaced with one of the “all-makes” coolants (non-silicate organic acid).

The class action suit was settled, but it is long past the time to put any claims in. The danger with an intake manifold leak is the coolant in the oil will displace the oil from the engine main bearings. To put things into perspective $600 is about 2 car payments.

I had the intake manifold gasket replaced on my 2000 Blazer in Feb 2004 and the coolant flushed and replaced with the green coolant. I had no further issues when the truck was traded in Nov. 2012.

Ed B.

There was a class action suit against GM for the problems Dexcool caused. But GM won that suit so there is no claim to file.

GM’s arguement was that the owners who had problems with the Dexcool failed to maintain the cooling systems of their vehicles properly thereby causing the damage to the cooling systems.


Intake manifold gasket leaks were “common” on GM 3.1, 3.4 and 3.8 engines. This would allow coolant to enter the crankcase.

I’m not sure what engine you have, but the local mechanic’s diagnosis sounds quite plausible.

There were several GM technical service bulletins related to this, but unfortunately I haven’t found one for your particular car and model year yet.

I had to have the intake manifold gasket replaced on a 1993 Oldsmobile I once owned. I saw coolant leaking and the intake manifold gasket was the problem. This was some time back–I sold the car 10 years ago and this probably happened several years before that. I think that my repair bill was about $350, so $600 is not out of line. As other posts have stated, this was a common problem on some GM engines. My 1993 Oldsmobile did not have Dex-cool in the system.

I did own a 2006 Chevrolet Uplander that did have the Dex-cool. I had the Dex-cool replaced with universal coolant. My son now owns the Uplander and has no problems since the Dex-cool was replaced with the other coolant.

Agree that you do need the intake manifold gasket, disagree that it is due to Dexcool. The jury was right on that one, it was the cheap gaskets that GM used at the time. If you have the 3,8 engine, do not be surprised if when they remove it to replace the gasket, that they find the lower half of the manifold to have a crack in it.