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Lubed the M38A1 yesterday and then took her off the blocks. Put in the batteries and checked the coolant level. Coolant was down 2 quarts! Hummm? I don't remember the last time I checked it in the fall, but it was never this low.

At any rate, the Willys started right up, so I drove it for a couple miles to let it warm up so I could change the oil and filter. When I poured the used oil out of the drain pan and into the 5 gal oil recycle bucket I saw the green Prestone.

So, before I get started with a repair, I'd like to know what is the most likely cause for coolant leaking into the F134 engine? Head gasket? Cracked block? Something else?

The engine runs fine and the exhaust has no white smoke (steam) or water dripping from the tail pipe. The temp gauge does not indicate any overheating.

Thanks

Fill it with water and start it up with the radiator cap off. After the thermostat opens accelerate the engine and if you have a rush of bubbles in the coolant the leak is a cylinder or head gasket leak. If no bubbles the leak is elsewhere in the block. The most common place is the distributor boss.

Thanks, Wes. So, I warmed up the jeep without the radiator cap on. Had my wife gun the engine over and over again for about 5 minutes. I;d say that I saw maybe half a dozen small bubbles during this 5 minute session. I assume this rules out a blown head gasket. Right?

You mentioned the distributor boss. I searched the forum and found some discussion on a copper tube/epoxy fix. Before I pursue this remedy, I want to make sure the leak is there. How would I confirm that the leak/crack is in the distributor well? I believe most, if not all, of the discussions were in reference to the L134, not the F134 engine. Do the castings for both engines exhibit the same weak areas around the distributor well?

Yes, and the easiest way to find most coolant leaks is with a coolant system pressure tester.

Running an engine with a large amount of coolant in the oil can damage bearings and other moving parts. Remember oil is lighter than water and the sump pickup is on the bottom of your oil pan - on startup your engine would have been lubricated with coolant - not a good thing. Best to change oil if you detect any water or coolant before running the engine.

Wes, how does pressure testing the cooling system help find where an internal coolant leak is? I understand the test can tell you that you have a leak, but don't understand how it tells you where the leak is.

Thanks

You pressurize the system then look for the leaking coolant. If you suspect the distributor boss you will need to remove the distributor then look down inside the hole where the distributor was. With the system pressurized you will see water coming out in that hole.

I believe there is a dye you can add to highlight any leakage or cracks