Dm685 e6-237 engine swap? Pushes coolant doesn't heat.

[Rcdvt]

Dm with e6 237 pushes coolant but doesn't heat. No thermostat. Truck sat for 10 years.  Didn't disconnect compressor as it won't push water idling or when compressors is running. Only does it under a load.  Any thoughts or suggestions?

Can you swap this to a 300 or larger Mack for more hp and ditch the twin stick trans for more gears at the same time. 

Truck is a beast and will surely last me.  Thinking at this point it is a cracked head.  Going to swap water pump next in case.

Thanks in advance.

[Joey Mack]

there is a tool that you put on the radiator cap nipple, and it will detect exhaust gasses in the coolant. NAPA sells it. It may be called a combustion tester....... An old timer taught me to take the thermostat out, put the thermo housing back on, and by-pass the compressor water lines ,only drain enough coolant to do this. then take the hose off the top radiator pipe and put it back on the thermo housing, and fill the cooling system to the top of the thermo housing nipple to where you can see the water, but there is a good 3" of hose above the water line. then take the belts off the water pump, and start the engine. after a minute or so, if the water perculates, then you have compression entering the cooling system. Usually it indicates a cracked head.. Good luck, Jojo

[Rcdvt]

Test showed exhaust gas in coolant. Pulled heads to get checked..... Injectors.... Let's just say we're currently building apparatus esses to remove a few

[mowerman]

boat anchor engine,,,unless your doing city work with it,,,,,dont throw your money  away...look around for a used 300 plus....i used to run one in the 80s....thier horrible for any kind of road work.......lots of fellas on here argue with me into the ground on this subject..loaded doubles on the grapevine.12 mph,,,,and that is no bullshit..lol.bob