I need help identifying an issue with my M35B diesel.
I had an overheating issue, and the red warning light came on. We turned off the engine and did not run it long.
The boat yard found a barnacle in the heat exchanger in the intake. They cleared it and ran Barnacle Buster. The engine ran fine at around 165 degrees for about three weeks.
Now, there is an issue with the antifreeze. It overheated at our slip after about five sails/motorings. We allowed the engine to cool down. I checked the antifreeze, and it was empty. I filled it with 50/50 antifreeze and water. It ran fine for again for a few sails/motoring. But the antifreeze seems to disappear. Not sure where it's going. Not in the bilge.
Please see the attached photos of the front end of the engine. I'm not sure what this is. It's a white power substance. It disappears when I spray water on it. Could this have some effect?
| Attachment | Size |
|---|---|
 Front engine | 2.97 MB |
It appears that sea water is leaking from your raw water pump. Need an image of the complete front of the engine. It may be raw water hose leaking.
If you are loosing antifreeze, that is a different problem. I would remove the heat exchanger and perform a pressure test at a radiator shop.
Keep us posted.
Sail La Vie 1999 Catalina 36 MKII, M35B-17031, Coyote Point, San Mateo, CA
About Sail La Vie
Two major possibilities for the raw water leak. One, when the engine overheated, it damaged the raw water pump, and thats why its leaking. Two, when the boat yard was working on the engine, they disturbed something in the raw water pump, or one of the hoses cracked when it was moved around. I have had leaking around the hoses attached to my raw water pump. I also rebuilt the pump when it started leaking out of the housing. A new pump was $600, the parts to rebuild the pump were $100. The seals just needed replacing, but I did the bearings and all interior parts while it was open. Of course it also ot a new impeller.
The coolant disappearing is much more of a concern. If there is no fluid under the engine or in the bilge, it has to be going out the engine exhaust or out the raw water system. Its either a leak in the heat exchanger, as suggested above, or possibly a crack in the engine exhaust manifold that heats up the water, or worst possibility, a cracked block or blown head gasket. The good news is the cracked block is easiest to diagnose. Check the oil. If its greyish or foaming, its a cracked block or head gasket. If its not, then its either the heat exchanger or exhaust manifold. Hope that its the heat exchanger, although both are easy enough fixes, if not cheap.