MD2020 overheat robustness

[Ric]

Hello,

A few months ago the overheat alarm on my MD2020 sounded. This was after a few hours running at highish rpm. I immediately shut down and didn't attempt to restart for at least a few hours. This happened once or twice more, until I eventually found the cause of the overheating.

At no time did I ever continue to run the engine after the alarm sounded - ie I immediately shut down and made no attempt to restart for some considerable time afterwards.

Nevertheless, I now find that the engine is consuming coolant - perhaps 10cc per hour or so. There is no evidence of external coolant leak. Would this signify a blown cylinder head gasket? And would the momentary overheating have caused this? I would have thought that the alarm would sound well before any risk of damage?

 

[tillergirl]

I think I would check the oil. Any water contamination there (milkiness) would tend to confirm heat gasket problems. Just possible I suppose that the overheat might have done something to the rubber end caps on the heat exchanger. If these are not tight it would permit coolant to escape into the raw water part of the heat exchanger. Have a look at those and try tightening the jubilee clips.

 

[richardbrennan]

I had a not dissimilar occurance on my 2030 a few weeks ago. The overheat alarm went off a few minutes after we increased the revs to around 3000 to make progress against the ebb streaming out of Portsmouth Harbour. We throttled back, shutting down was not an option at the time, and the warning ceased almost immediately. The cause was a partially blocked exhaust elbow which, I understand from the engineers that fixed it, is a fairly common occurance with these engines. I have since had a new elbow fitted and this seems to have cured the problem and I do not seem to have suffered any further damage. However, your coolant must be going somewhere and I think I would get some expert advice. If you are anywhere near Portsmouth, Rob at Motortech in Haslar Marine has considerable experience with these engines and diagnosed the fault I had over the phone.

 

[Bav32]

No overheating but I had a similar loss of coolant which was being lost down the clear plastic overflow pipe near the filler cap on the heat exchanger.
I declined the advice of the local Volvo agent to fit a new cap (mega beer tokens) and adjusted the existing device. There is a screw adjustment with tee piece, fitted to the filler cap which was not exerting enough downward force to create a pressure sealto the fitting on the heat exchanger and allowing coolant / vapour to exit via the pipe.
A bit a fine tuning of the height resolved the issue.
Worth noting that the threads on the fitting were quite tight. After removal and cleaning, I applied a little PTFE tape over the threads which made adjustment much easier.