301 compression in coolant

I have a 190XT diesel that is getting compression in the coolant system, took head off and had it checked at a local head shop and he could find nothing wrong with it, no cracks, no warpage, etc.  The head gasket looked good, no obvious leaks, pistons look ok, no sign of water inside sleeves, no water in oil and no oil in water but when you rev the motor the cap had better be loose or else.  Any ideas?  We can't see any sign of the sleeves leaking around the top either, guessing a busted sleeve?  Maybe someone else has experienced this condition and can help.  Thanks.

No sign of coolant in the oil ?....if there was ANY shaving cream like material under the valve cover, or on the bottom side of the oil fill cap, you had coolant in the oil. I'm like Mack, it's probably the cylinder head and they can't see it or don't know where to look. Sometimes the floor of an exhaust port get cracked and they never look there.

My 6060 did the same thing.  A few tiny holes in the sleeves of two cylinders above the top of the piston rings in the compressions stroke.  No oil in the water or water in the oil was noticeable but sure bubbled the rad cap over.

I'll throw another vote for checking the sleeves for pin holes.  Maybe you can find a plug from a plumbing supply store that will fit, drill a hole, put a fitting on it, and hook it up to an air pressure source at some pressure and recheck for bubbles on each cylinder with the piston at BDC.  Just an idea.  Not sure how well the rings will seal to hold the pressure, but it shouldn't cost too much to gather the parts to give it a try.  That's assuming you can't see the hole and don't want to take the sleeves out.  It may not be a bad idea to take all the sleeves out anyway to check for cavitation and possibly overhaul the engine, because if one sleeve has a problem with cavitation, it's likely the others are not far behind and the bottom bore where the o-rings seat has some good pitting.  I would make sure the head was pressure checked before tearing the engine down.  Did the head gasket have any signs of failure?  Did you have any water in the oil?  Even if it's not enough of a leak to collect in the bottom of the pan, it could still have done some damage to the bearings.

Hurst


Edited by Hurst - 09 Feb 2012 at 1:24pm

Pin holes in the sleeves usually make for coolant in the oil, not so much compression in the coolant.   A cracked cyl head makes compression in coolant more times than not.  Ive had a good used magnafluxed head check bad with the pressure tester.  Pressure testing is a pain in rear, but will tell the truth if correctly done.    I fabricated the pressure testing parts using long bolts and heavy iron with cut inner tube seals.  When the copper injector sleeves came about you just about had to pressure check them.  Good luck