Missing Coolant - CAT 3208

Recently my port 3208 has a new problem. I can fill the coolant tank, run the engine up to temp burping it, so it's completely full. Turn the engine off then check it when cooled down and the tank is bone dry. No coolant anywhere in the engine room. Not a trace. I pressure checked the system when cool and it does not hold pressure, it leaks down pretty quickly. I crawled all over it while pressurized and not even a small leak. How do I diagnose the location of the leak without taking things apart? The head gaskets have been replaced by a very good technician and the sea trial went off perfect. How do I go about finding the leak? Thanks up front for your help.

The coolant is bleeding into the raw water system at the heat exchanger which is the tube on the top front of your engine.

Pressure test the system with the heat exchanger in place, then bypassed. That would confirm the heat exchanger before tearing into it.

tiltrider1 said:

The coolant is bleeding into the raw water system at the heat exchanger which is the tube on the top front of your engine.

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Most likely.

Drain the sea water section of the HE and leave the lower sea water hose off. Use a pressure tester to pressurize the cooling system and look for coolant out of the HE lower sea water hose outlet.

NOTE: Even if you do find coolant from the HE there's a small possibility that there's more than one leak. Therefore, after the test is complete, DO NOT try to start the engine until you have turned it over by hand at least 720 degrees of crankshaft rotation. This test can hydrolock the engine if there's a leak in a head gasket and if it fires with a hydrolocked cylinder, it will bend a connecting rod.

Xfirepop said:

Recently my port 3208 has a new problem. I can fill the coolant tank, run the engine up to temp burping it, so it's completely full. Turn the engine off then check it when cooled down and the tank is bone dry. No coolant anywhere in the engine room. Not a trace. I pressure checked the system when cool and it does not hold pressure, it leaks down pretty quickly. I crawled all over it while pressurized and not even a small leak. How do I diagnose the location of the leak without taking things apart? The head gaskets have been replaced by a very good technician and the sea trial went off perfect. How do I go about finding the leak? Thanks up front for your help.

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Fist thing is I'd pull the dip stick and look at the color of the oil. ANY milky color is a disaster as your rod and main bearings do NOT TOLERATE ANTIFREEZE.

mrfixit48 said:

Fist thing is I'd pull the dip stick and look at the color of the oil. ANY milky color is a disaster as your rod and main bearings do NOT TOLERATE ANTIFREEZE.

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I seem to have posted that before I was done so here's the rest of the story. I spent 20 years working for the Cat dealer in Alaska at the time when the 3208 came out so have some.knowledge of them. They were designed as a throw away engine and do not have cylinder liners like other diesels do. You can have the block bored and fitted with OS pistons but that's a chore. The anti freeze is going either into the engine through the oil cooler or out the heat exchanger with the raw cooling water. If you have milky oil address the oil cooler and then flush the engine about 4 times to clean the antifreeze out of the oil passages. If you have lucked out and the oil is clean then you need to inspect the heat exchanger and correct any issues you find there. You still could have a bad head gasket even though they are new. Won't be the first time that's happened but check your coolers first.

It’s also possible you have a leak in the water heater coil.
Also you may wish to buy a head gasket leak tester. About $20 on Amazon to give you peace of mind about the head gaskets.

Don’t forget the transmission cooler. Check tranny oil level

Just an update. The caterpillar mechanic came by and pulled the exhaust manifolds loose and said that the water draining out indicated that there was a failure possibel crack in the water jacket. Then I came down with COVID, just the latest minor version. I'm waiting out the isolation to resume diagnosis.