Cooling system experience: Universal 18M

[Bob Ohler]

My "new" CD30 had a leaking heat exchanger. I found a radiator repair shop in Annapolis, that agreed to repair the exchanger. They gave it the acid bath treatment, pressure tested the unit and installed the new zinc that I provided.
I reinstalled the heat exchanger, added what anti freeze I could to the resevoir and started the engine. I knew something was not right, as I thought that the temperature gauge had been running at a much cooler temp. I was now looking at a gauge reading around 200 degrees.
I went in search of advice. The local diesel mechanic informed me that I had an air pocket in the system up by the hot water heater. First he told me to get a long piece of hose, connect it to the engine, but hold the hose higher than the hot water heater and add coolant. This sounded like a pain. But off I went. I opened the starboard locker by the water heater, and noticed the horizontally mounted tank near the heater with what looked like a radiator cap. I removed the cap to find a dry tank. Back to the mechanic for more discussion. He said this is called an expansion tank. Open the cap there, add antifreeze / water mixture, start the engine, run it half throttle in gear, allow the bubble to rise to the top of this expansion tank, add more antifreeze if necessary, and replace cap. She was now back to running around 160 or 170 degrees.
MORAL TO THE STORY: The mechanic says,that this upper tank is where the coolant level should be checked, NOT the resevoir down on the engine.
Bob O.



bobohler@chesapeake.net

[Tom]

I'm surprised that did it for you, Bob. Usually when you get an air bubble in the coolant system it's a struggle to get it out. I've always had ro remove the coolant hoses one at a time from the expanson tank to the water heater and blow back through them to compress the air bubble and force it through the system. Don't be surprised if after you take it out and run it hard for half an hour or so the engine overheats. You may not be out of the woods yet because at idle it will often work OK even with the bubble in there, but when it gets stressed it won't keep up with it. When you fill the expansion tank don't fill it right up to the top. Leave a little room for the coolant to expand when it gets hot. When the engine is running at operating temperature the tank will appear full, but when it cools down it will shrink down a little bit. It's just like that plastic overflow bottle on your car, i.e., fills up when it's hot and goes down when it's cool. Keep an eye on the temp for awhile to be sure the bubble is cleared.

My "new" CD30 had a leaking heat exchanger. I found a radiator repair shop in Annapolis, that agreed to repair the exchanger. They gave it the acid bath treatment, pressure tested the unit and installed the new zinc that I provided.
I reinstalled the heat exchanger, added what anti freeze I could to the resevoir and started the engine. I knew something was not right, as I thought that the temperature gauge had been running at a much cooler temp. I was now looking at a gauge reading around 200 degrees.
I went in search of advice. The local diesel mechanic informed me that I had an air pocket in the system up by the hot water heater. First he told me to get a long piece of hose, connect it to the engine, but hold the hose higher than the hot water heater and add coolant. This sounded like a pain. But off I went. I opened the starboard locker by the water heater, and noticed the horizontally mounted tank near the heater with what looked like a radiator cap. I removed the cap to find a dry tank. Back to the mechanic for more discussion. He said this is called an expansion tank. Open the cap there, add antifreeze / water mixture, start the engine, run it half throttle in gear, allow the bubble to rise to the top of this expansion tank, add more antifreeze if necessary, and replace cap. She was now back to running around 160 or 170 degrees.
MORAL TO THE STORY: The mechanic says,that this upper tank is where the coolant level should be checked, NOT the resevoir down on the engine.
Bob O.

TomCambria@mindspring.com

[Bob Ohler]

After filling the expansion tank near the hot water heater, I ran the engine with the cap off the tank, at half throttle, in gear while the engine heated up. When the coolant heated up, and as the bubble was working its way out of the loop, the coolant actually did bubble over some into a coffee can that I had close at hand. The coolant level then receded. Per the mechanic's instructions, I topped off the tank, leaving the level about an inch down from the top. I took the boat out yesterday afternoon. We had no problem with over heating, either on the way out, or motoring home after the fickle wind died.
Thanks for heads-up! I think that I may have the situation corrected.

Bob O.

I'm surprised that did it for you, Bob. Usually when you get an air bubble in the coolant system it's a struggle to get it out. I've always had ro remove the coolant hoses one at a time from the expanson tank to the water heater and blow back through them to compress the air bubble and force it through the system. Don't be surprised if after you take it out and run it hard for half an hour or so the engine overheats. You may not be out of the woods yet because at idle it will often work OK even with the bubble in there, but when it gets stressed it won't keep up with it. When you fill the expansion tank don't fill it right up to the top. Leave a little room for the coolant to expand when it gets hot. When the engine is running at operating temperature the tank will appear full, but when it cools down it will shrink down a little bit. It's just like that plastic overflow bottle on your car, i.e., fills up when it's hot and goes down when it's cool. Keep an eye on the temp for awhile to be sure the bubble is cleared.

My "new" CD30 had a leaking heat exchanger. I found a radiator repair shop in Annapolis, that agreed to repair the exchanger. They gave it the acid bath treatment, pressure tested the unit and installed the new zinc that I provided.
I reinstalled the heat exchanger, added what anti freeze I could to the resevoir and started the engine. I knew something was not right, as I thought that the temperature gauge had been running at a much cooler temp. I was now looking at a gauge reading around 200 degrees.
I went in search of advice. The local diesel mechanic informed me that I had an air pocket in the system up by the hot water heater. First he told me to get a long piece of hose, connect it to the engine, but hold the hose higher than the hot water heater and add coolant. This sounded like a pain. But off I went. I opened the starboard locker by the water heater, and noticed the horizontally mounted tank near the heater with what looked like a radiator cap. I removed the cap to find a dry tank. Back to the mechanic for more discussion. He said this is called an expansion tank. Open the cap there, add antifreeze / water mixture, start the engine, run it half throttle in gear, allow the bubble to rise to the top of this expansion tank, add more antifreeze if necessary, and replace cap. She was now back to running around 160 or 170 degrees.
MORAL TO THE STORY: The mechanic says,that this upper tank is where the coolant level should be checked, NOT the resevoir down on the engine.
Bob O.

bobohler@chesapeake.net