120 Diesel Lehman Over heating

If cylinder compression is getting to the cooling jacket, then coolant will be getting into the cylinders when the engine is stopped. Evidence of coolant in the cylinder(s) will likely be there and tell you of a head gasket problem, which would explain the pressure buildup in the coolant jacket. This would verify a head gasket issue in that area without pulling the head. I have been doing diesel repair/rebuild for 40 years and can tell you it this works (assuming the injectors aren't in a pre-combustion chamber). Another way is to use an exhaust gas analyzing test bench and sniff for CO at the coolant filler cap. Though not many lay persons are going to have test bench.

hobbystuff said:

Also - I would install the Expansion Tank/Recovery mod from American Diesel. It doesn't look like you have this on your engine.

i have it on mine and it sure helps me keep an eye on coolant levels.

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Just an FYI, i run a Lehman 120 diesel on a small 26 downeast. I would run at 2400 for hours. I would always check the engine before i started it again and always lost coolant. (Never overheated, never got hot)

I thought it was a head gasket. Put an overflow tank on and its been spot on ever since.

Maybe not the same issue, but the tank suggestion is a good one

Alisske said:

Just an FYI, i run a Lehman 120 diesel on a small 26 downeast. I would run at 2400 for hours. I would always check the engine before i started it again and always lost coolant. (Never overheated, never got hot)

I thought it was a head gasket. Put an overflow tank on and its been spot on ever since.

Maybe not the same issue, but the tank suggestion is a good one

Click to expand...

Having a tray under my L120s, I could see the lost coolant,out of the header tank and into the tray. With a tube on the overflow tube, it goes to the overflow/recovery tank.