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

Jeffrey via Public-List public-list at lists.alberg30.org
Thu Sep 11 10:43:58 PDT 2014

Hi Randy,

I'm no diesel mechanic,  but I would address both the thermostat and the
heat exchanger at the same time. You'll need to drain the coolant system
some to test/change the thermostat anyway, so unplugging the heat exchanger
and giving it a good cleaning at the same time makes sense to me.  I don't
think I'd take the risk running strong acid through the system, the
exchanger is easy enough to clean when removed.  And, by actually opening
up the exchanger you may find stuff in there that the acid won't dissolve.
If you are like me you'll motor just a little happier knowing how clean the
exchanger is when you are finished.

Good link on Westerbeke & Univeral heat exchangers.

When you put everything back together, be careful to properly bleed out all
the air from the cooling system. An air bubble can lead to overheating

I would not rule out the external screen on the through hull. Plastic bag
trash can get in there and foul that up.  I removed the screen on water
intake, and just use a straight open through hull, preferring to let the
inboard filter catch debris.


On Thu, Sep 11, 2014 at 12:55 PM, Randy Katz via Public-List <
public-list at lists.alberg30.org> wrote:

> 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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Jeffrey Fongemie



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