98 6.5L TD G3500 Chev van coolant leak

[Roy Malone]

Engine has 281,000 miles. Coolant disappears at about one gallon per hour. No visible external leaks(dye used in coolant and no external leaks around intake manifold or head gaskets). Pressue test shows drop when engine is running. Oil on dip stick looks good. Underside of oil filler cap is milky and some vapor can be seen coming out small brass fitting in middle of filler cap. No loss of engine power apparent. Exhaust is clear on startup and when running. Water temp 180-185 when running. Automatic transmission fluid clear. Intake manifold gaskets would be easy. Cost of head gaskets or cracks of $2,000 is almost too much for this engine mileage. Any ideas on problem or solution??

[richard7]

A gallon an hour is a lot. You should see something. Have your engine oil analysed.

For me, it seems to be a cracked block at the bottom of the liner, with coolant going in the combustion chamber. :( Sometimes, it only leaks when the engine is hot or the engine running because of water pressure, heat and vibration.

[Roy Malone]

Thanks Richard7 for your reply. I now have water in the oil and one cylinder on the drivers side has 45lbs lower compression than the others. Other replys suggest head gasket of cracked block. Plan to remove that head to investigate.

[Roy Malone]

Thanks Richard7 for your reply. I now have water in the oil and one cylinder on the drivers side has 45lbs lower compression than the others. Other replys suggest head gasket of cracked block. Plan to remove that head to investigate.

[Roy Malone]

Replaced head gasket on left head that had 45lb lower pressure on cylinders 3 & 4. Leak still persists while running and not running. Found 0 ring in water passage of head about the size of a quarter(pvc grommet size). Looking for source. Any ideas welcome. Roy