I have been thoroughly enjoying a warm summer and warm fall here in SOCAL. A couple weeks ago, while coming back from a wonderful sail and approaching sunset, I had a sudden overheat issue. I managed to limp back into port and observed the following symptoms during the overheat sail:
1. Coolant steaming (later found that the thermostat butterfly valve had let some coolant out.
2. I had plenty of raw water flow so no obstruction to the impeller.
After arriving back into the slip I have been steadily troubleshooting various causes for the overheating and I think I've eliminated the usual suspects. Thus far I have verified and/or changed the following:
1. Raw water strainer clear and no obstruction
2. Removed and opened up HX. Verified that all lines are clear. (just cleaned it out in the spring)
3. Changed out my oil after the overheat
4. Flushed and changed and burped the coolant.
5. changed hoses to the HX (Raw water and coolant)
6. Burped the coolant line to the hot water heater (per the tech wiki instructions
7. Tested and verified that the thermostat is working properly.
During the overheat the onset was sudden. Although there was loss of coolant it was due to the butterfly valve on top of the thermostat housing and has since not leaked. I have opened up the top of the coolant tank and watched for flow from the coolant pump after the thermostat is supposed to open up but no observable flow.
I'm kind of at my wits end here. The coolant pump has shown no signs of failure or weeping or making any noises but at this point it appears to be the last possible point of failure.
As stated earlier, the onset of the failure was sudden. No prior indications or noises. It seems odd that the coolant pump would fail since I only have 1100 hours on the engine.
Any ideas? and...Although I have become very proficient in performing minor repairs and preventative maintenance, a water pump is making me pretty nervous.
I would like to hear thoughts about possible causes of the overheating and any information about changing out the coolant pump (procedure tips and models number)
Anyway... Help! I'm about to call in the engine guy and admit defeat.
