380 sec 1983,water in #6cyl

[pollockd17]

No bubbles in expantion tank, 150 psi across the board, valve action is
ok, I'm thinking crack in head, 150,000 miles on engine, any ideas???

[Air&Road]

Well, the head will have to come off anyway, so you will know then. If the water is getting in the cylinder through the head, it is probably not a crack, but due to corrosion from water jacket to combustion chamber. A good head machine shop can weld it up.

Has the antifreeze been changed every couple of years. Lack of antifreeze maintenance will cause the corrosion issue I described.

[97 SL320]

Do a leak down first and see if it makes it's way to the cooling system.

Does this motor have any coolant passages in the intake manifold?. I've seen gaskets leak coolant to intake.

[nulu]

Early engines had threads in the head that stripped or were loosing tension, perhaps thread kits for block holes are needed with bolts too.

[duxthe1]

A crack in the block will cause water in the cyl without the typical head / gasket failure symptoms. An inspection with a bore scope would be in order.