91 Lesabre losing coolant

my 91 lesabre is losing coolant somewhere. Not in the oil, no leaks on the driveway, can't seem to find anything.

I filled the radtiator and then the overflow tank about 3 inches above hot full on Sat, today the overflow is almost empty and the radiator in about an inch or two low.

The car has only been driven about 15-20 miles total on two trips.

any ideas?

I've heard you can pull the spark plugs and see evidence of coolant on one or more. That would indicate a blown head gasket and coolant is going out through exhaust.

Inspect the top the engine where the intake maniforld (gasket) is for little puddles. A leak there would evaporate from the engine heat.

I filled the radtiator and then the overflow tank about 3 inches above hot full on Sat, today the overflow is almost empty and the radiator in about an inch or two low.

As much as it's losing you should be able to see it! Just drive the car a short trip and then check it as you park it. Let it idle for a few minutes to build up more pressure...

ahh ha, I have a 03 Pontiac Montana with a recently repaired upper intake manifold gasket (haha, caught it at 33K miles under warranty). Lots of RTV bulging out of the gasket area.

As I look at the 3800 in my Buick, it looks the same...like there has been some work done at some point in the past. Not any pooling coolant, but I will try the short drive/driveway test.

Come to think of it, the car has always used coolant, but it only goes down to the level I'm seeing now (~two inches down in the radiator)

Oh well, the body and suspension are shot to hell. Too bad, because it only has 113k miles. Bought it a year ago for my wife to drive to work...$650. I feel I've got my money's worth. I'm going to go put it in the for sale lot uptown for $500 and see if I get any bites.

Anyone got an 80's diesel mercedes for sale? :)

Yep, forgot about the intake manifold on 3800 engines. I have seen bunch of posts about repairing that. I think GM got it right about 1999-2000.

Inspect the top the engine where the intake maniforld (gasket) is for little puddles. A leak there would evaporate from the engine heat.

Hmm, I think you're on to something there. I took a look at what I believe to be the upper intake manifold gasket. Just above the transmission on the drivers side, there is a little valley where a large gunky oil/grease spot is, and there is evidence of leakage.

I"ll try to post some pics later

Hmm, I think you're on to something there. I took a look at what I believe to be the upper intake manifold gasket. Just above the transmission on the drivers side, there is a little valley where a large gunky oil/grease spot is, and there is evidence of leakage.

I"ll try to post some pics later

I cleaned up that area and refilled the radiator and resivoir. Then I took it for a drive, and checked things over. No leakage, but IO did notice a pretty steady stream of air bubbles coming up in the overflow tank.

Hmm

I believe your describing a blown head gasket or cracked block. Take it to a shop and see if they can detect combusion gases in the cooling system. You may even be seeing some white smoke coming out the exhaust. :2cents:

One way to test for a leak from the cooling system to the combustion chamber is the radiator pressure test. Most shops have a cap to install on the radiator with a pump to pump about 15 psi in the cooling system. It should hold the pressure for more than 15 min if you do not have a leak. Another way is to do a leak down test. You apply 100 psi to the combustion chamber through the spark plug hole with both intake and exhaust valves closed. You can measure the percentage of leak down and usually here where the leak is going. If it is going into the cooling system, you will see air bubbles in your radiator. If you suspect that you have a cracked head or blown head gasket, do not leave the radiator cap on during the leak down test, or you could blow your radiator, hoses & heater core!!