LIM gasket repaired but losing coolant internally [Archive] - Forum


View Full Version : LIM gasket repaired but losing coolant internally

03-12-2008, 07:31 PM
I've been working on my brother's 01 Malibu (3.1 but same parts as 3.4). I've come here before for information about my daughter's 99 Grand AM so I'll run this by you guys. Sorry about the long post and if it's too much detail.

The LIM gaskets were leaking badly externally, so I did a cold compression test to also check for internal leakage. Everything was within spec according to the factory service manual (within 20% highest reading cylinder to lowest). Also, no oil in the coolant or coolant in the oil. So I figure that there is no internal leaking and the heads and head gaskets are good. However, I did not see the car in running condition to check for exhaust smoke, etc.

So I changed the LIM gaskets very carefully, torqued all bolts, etc. Then I did a cold coolant pressure test for about 4 or 5 minutes at 15psi and it held (usually meaning no internal or external leaks). When I started it up, the exhaust has thick white smoke which looks like burning coolant, from startup and throughout a fairly long period of running. Also, the coolant tank started to overflow (it was below the full mark when I started the engine). Then, when the engine cooled enough to remove the coolant tank cap, the coolant was steaming some white smoke. Also, the coolant was a quart low (much more than overflowed out). So I figured that the head or head gaskets are leaking coolant into the cylinders. But why did the pressure hold at 15 psi when I tested it?

So I thought maybe there is a head crack that opens up when the engine is warmed. So I ran the engine to warm it again, then did another coolant pressure test but this time on the warm engine. Again, it held steady at 15psi.

So I am at a loss. I don't know why the initial compression test was good and the cooling system holds pressure during the pressure test, but yet the engine is burning coolant. How is it getting into the cylinders?

03-14-2008, 07:45 AM
Coolant Test Specs (

Could be a head Gasket? Do the cylinders hold pressure?

03-14-2008, 08:31 AM
Sounds to me like yours is going to be a pain to finish bleeding. If the cooling system is holding pressure for a long period of time I wouldn't worry about a headgasket leak so much.

The thick cloud of white smoke could be coolant that accumulated in the cylinders during the repair. I'd top off the coolant, pressure the system to 17 psi and open the bleeder to get air out of it. Then pressure back up and repeat for a little while. After that start the car again and let it run with the cap off. It may boil over again so be prepared with a catch pan under the passenger frame rail.

If it boils off, shut the car off and top off the coolant. Then install the cap and let the car cool. Repeat process as needed. Sometimes it takes awhile to bleed the more difficult ones.