[Public-List] Overheating diesel engine-- 2 questions or more

[Randy Katz via Public-List]

Greetings, Folks,

On the last trip, my Universal diesel showed an increase in temp. from the
normal 160 degrees to 170 after running for a couple of hours at cruising
speed of about 5 kts.  This hasn't happened before. (1200 hrs. on the
engine).

I assume this temp increase is significant.

I cleared the sea water filter feeding the engine. (It was clogged the
first time, and cleaning it resulted in lower temp. though with another
half-hour of running the temp rose a bit again.)

The exterior hull screen should be all clear (hauled out a month ago). The
seawater filter is now clean. So I'm wondering if it's the heat exchanger
calling out to be cleaned. Or perhaps the thermostat.

QUESTION--Is this likely to be a thermostat problem? That would be great as
it would be easy to replace. I understand the basics re: testing that part
and a replacement would be simple.

QUESTION--Should I expect a clogging heat exchanger could be the problem,
given the 1200 hrs. on the engine? Mechanics suggest there's no need to
bother with this until "it's really necessary." How does one know when that
is?

Is it reasonable (as recommended by a dockmate) to try clearing the heat
exchanger by running vinegar (or acyliatic acid-- splg?) from a bucket into
the engine, letting it sit for an hour or so, and then flushing the thing
out with seawater?

Any advice would be appreciated. I'll start with the thermostat and see
what happens.

I can imagine spending plenty of time trying to pull out the exchanger with
the engine in place--if the thermostat doesn't do it, can I assume that the
heat exchanger is the problem?

Many Thanks,

Best Regards,

Randy
#249 Simple Gifts
Seattle/Bellingham

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