Strange coolant leak; head gasket ???Long

[jackfisherman]

Help; I think I might have a leaking head gasket or cracked head near the rear of the drivers side. Coolant appears to be coming from this area but hard to tell. I pressure tested rad to 16 psi and it is slowly dropping but can't locate. I also kept the tester on and ran the engine; it pressurizes to 19psi at idle ; is this to much meaning combustion gases are entering rad. Checked water pump weep hole, frost plugs on the sides and block heater; no leaks. No bubbles in rad at cold start up. Only very slight bubbles in coolant reservior tank when warm and pressured up (10 lbs rad cap). No white smoke; only grey mist on cold start (-10F) normal. No moisture from tail pipes. No milky oil or condensation on oil cap. Seems to seep more after a long run time. Is there a chance that one of the two frost plugs behind the ring gear is letting go and blowing coolant up near the drivers side head. Please help. Sorry for long post.

Jackfish
87 6.2 sub 140,000 miles

[john8662]

This sounds like the coolant blockoff plates on the back of the heads. One of them is covered up by the glow plug controller and the other one probably houses a temp inhibit switch. I've fixed coolant leak problems in these areas before, and they look like they're leaking elsewhere. These block off plates use the same gasket as the thermostat crossover manifold does, when you're parts chasing.

The bubbles you're seeing in the cooland recovery tank, are they consitant with the engine running (steady stream of bubbles)? Or, do they just come one at a time, just random when you're watching it? It could be you're just low on coolant, from the leaks externally.

I have yet to find a 6.2 that was leaking coolant from the block via the freeze plugs on the back side of the engine.

Good luck, keep us posted!

[jackfisherman]

John; I have check both block off plates and noticed no evidence of leaks. Gave them a little torque but the bolts seem pretty tight. Looks like there is a constant amount of very small bubbling in the coolant reservoir. Thanks.

[john8662]

That does sound suspiciously like head gasket problems as you have suggested. You're next move would be to find a radiator shop that tests for comustion gasses in the cooling system, most shops have the equipment to test this.

[jackfisherman]

I have heard that very few head gaskets will blow to the outside of the head causing coolant leakage to the exterior. I am planning to pressure wash the engine and have a closer look once it warms up outside.

[john8662]

External leaks are not usually common with head gasket failure, mainly pressure in cooling system or coolant in the cylinders. Take a closer look, I'd be interested what you find.

[jackfisherman]

John; what do you think about dropping a sealer into the rad to get me by. Some auto forums say they have had luck with this stuff; or am I playing with fire.

[john8662]

If you truely have a head gasket failure, the problem will only get worse, and the sealer will likely start plugging up the radiator and heater core and other ports. Since you have an external leak, wash the engine off real good, let it sit for a few days (dry out completly). then crank up the engine, get it up to full operating temp, park it. Pull the air cleaner, and look for leaks, I would still look for the plates on the back of the heads for leaks. But at any rate, while still hot you will be able to find pressure leaks from the pressured up system.

[Ratau]

Just a wild shot in the dark.

Will the florescent additive in the antifreeze glow under an Ultra Violet lamp like the florescent additive inside the air con system? Maybe one could trace the leak that way.

Danie