How to Flush Coolant System, 1982 Grand Banks Lehman Diesel 120

[kurt.reynolds]

I am replacing exhaust elbow gasket on my 1982 Lehman 120. I drained the coolant from the heat exchanger drain and only got about 2 gallons out. Internet says the Lehman 120 holds 20 qts of coolant.

What is a good way to flush the coolant system after repair. I assume I will fill it with plain old water to test, then want to flush and refill with antifreeze/distilled water.

Thanks! Pictures of disassembled elbow.

 

[hytedin]

Call Brian at American Diesel:


https://americandieselcorp.com

 

[DavidM]

I can't comment on the specifics of the Ford Lehman, Brian is your best source for that, but I can comment on the generic process:

Drain the coolant by opening lower drains that Brian can advise on as well as any hoses to the water heater. make sure the fill cap is off while draining. Fill with fresh water and run the engine until the thermostat opens and drain. Then fill with 50/50 antifreeze until fluid is visible at the fill nozzle. Then run the engine at the dock under moderate load. Most engines will drop the level a bit as air is pushed out so keep it full until the thermostat opens and then put the cap on and continue heating until the temp stabilizes.

If you have a water heater connected to the coolant system you may have to run the engine at a higher speed to force air out of that system. Do it carefully with the cap off and fill with antifreeze if the level drops. If the coolant is really hot and almost boiling at the filler neck, then it is probably fully vented.

This will work for 95% of engines, but like the Cat 3208NA thread, some need more help. This usually means venting air out through another fitting on the engine like the temp sensor. Again Brian can advise on how to do that.

David

 

[syjos]

I clean and flush the FW cooling system on Sandpipers FL 120 every 10 years.

I pump the coolant out via T fitting on the heater hose to hot water tank using a utility pump. The thermostat is removed, expansion tank reinstalled and the T closed. Fill with water and Prestone Radiator Flush and Cleaner per instructions. Run the engine for the recommended time. Pump out the fluid.

Hook up a garden hose to the T. The water will come out of the fill opening in the expansion tank. Either buy the Prestone Flush Kit and use the filler neck adapter or modify an old radiator cap by attaching a hose connector to it. Pinch the heater hose on one side of the T and turn on water and run for a while. Reverse the direction of flow by pinching the other side of the T and turn on the water. Reversing the water direction should dislodge any debris trapped in the coolant passages.

When the water coming out of the cap is clean, pump out or drain the system. Reinstall the thermostat and fill the system with new coolant and distilled water or premix.