Thread: Head Gasket? Or LIM ??

Check your intake gaskets.

The intake gaskets would be my first guess since thoses are a promblem on the 3800, and 3400. sure headgasket could cause it but is less likly. I would replace the lim gaskets if they have never been replaced yet and get the revised aluminum ones. (they are hard to find locally) zzperformance.com has them if you cant get them locally.
If your doing this yourself You will need....

1. Upper intake manifold gasket
2. Throttle body gasket (normaly comes with UIM gasket). Also the throttle body doesnt have to come off.
3. Lower Intake manifold gasket (Need black RTV should come with the gasket set)
4. 10 quarts of oil. I like to change the oil right after replacing the gaskets. I let the car run for awhile untill i get air out of coolant system and if everything checks ok then i change it out once more just make sure no coolant/ dirt is in the oil. Spun bearings arnt fun
5. coolant. good time to change the thermostat (need gasket for thermostat) and change to the green or yellow coolant! if you still run the orange dexcol s**t.
6. somthing to clean the gasket surface with. scotch brite works good.

That should be about it... there maybe more though.