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01 Malibu white smoke in exhaust

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New User

Mar 12, 2008, 7:08 PM

Post #1 of 4 (1627 views)
01 Malibu white smoke in exhaust Sign In

I've been working on my brother's 01 Malibu (3.1 engine). The lower intake manifold gaskets were leaking badly externally (a common problem on this GM engine), 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 lower intake manifold 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 turned it off and 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?

Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 12, 2008, 7:24 PM

Post #2 of 4 (1622 views)
Re: 01 Malibu white smoke in exhaust Sign In

Just holding 15psi could work but clearly it does leak. It could test out with compression also as ok.

Compression pressure alone could spike way up there in psi while running and a crack could open more or less at assorted temps unseen without going there.

You could put each cyl on TDC and pressure up to the highest a compressor's air gives you and perhaps see the one(s) that bubble back to reservior but that still doesn't tell exactly where the problem is - gasket or flaw in parts.

Machine shops specialize in testing heads and parts which is why it is suggested to send head out when getting in there to replace even just gaskets,


Double J
Veteran / Moderator
Double J profile image

Mar 12, 2008, 10:30 PM

Post #3 of 4 (1620 views)
Re: 01 Malibu white smoke in exhaust Sign In

Just to add...
There can be a real slow pressure loss...meaning you may have to leave the pressure tester on at 15 psi overnight,checking periodically and repumping the pressure to 15 psi if there is a gradual loss....then pull the plugs and look for signs of coolant in the cylinders...

Just a thought...

New User

Mar 13, 2008, 9:06 AM

Post #4 of 4 (1617 views)
Re: 01 Malibu white smoke in exhaust Sign In

Thanks for your thoughts guys. Someone else also told me about a test called a Combustion Leak Test (or Block Tester) where it tests for exhaust gases in the cooling system. Sounds easy to test, so I ordered the kit from NAPA (part number 700-1006 if anyone is interested). I just wanted to be more certain that it's definitely a head gasket/head problem.

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