[Public-List] Overheating diesel engine-- what I found

[Wes Gardner via Public-List]

Randy,

Engine missing??? Thieves abound...sorry, couldn't resist :-)

Glad you discovered SOMETHING...I would have hated to go through that and
find NOTHING...

Wes

On Mon, Sep 22, 2014 at 11:31 AM, Randy Katz via Public-List <
public-list at lists.alberg30.org> wrote:

> Greetings,
>
> I sent in the note below a few weeks ago. Since then I did a little digging
> around in the cooling system of the Universal M3-20B diesel and seem to
> have resolved the problem--for now.
>
> The main symptom was overheating by about 10 degrees at higher rpms. (The
> temp. went up from a normal of about 160 to 170 after 30-60 min. running at
> 2500 rpms.) I noticed that dropping rpms = cooling temps. This made me
> suspect the heat exchanger (not serviced in the 1250 hrs. since the engine
> was new).
>
> I thought if it were a thermostat problem, the temp would remain high.
>
> To that end, I removed the heat exchanger end cap and checked inside using
> a mirror and flashlight. It was very tight but I could see clogging of a
> number of the the tubes in the upper half of the exchanger. (I ascertained
> that sea water from the impeller enters the bottom of the exchanger, runs
> its length to the other end, goes up to the top set of tubes, and exits out
> the top and to the exhaust system. A one-pass arrangement, I believe this
> is called.)
>
> Given the cramped conditions at the open end of the exchanger, I managed to
> poke a couple of flexible tools (copper wire, a narrow SS band) and
> carefully ream out what I could of the clogged tubes. I understand that one
> must be very cautious because the soft tubes are relatively easy to damage.
> Tubes at the bottom of the exchanger (in water-in end) seemed clear.
>
> During last weekend's trip to Cypress Island (a couple of hours motoring
> time in flat calm conditions) the temp stayed put at about 162 the whole
> time.
>
> My conclusion is that at some point pretty soon, I'll need to have the heat
> exchanger properly cleaned. But I was very relieved to find that my
> tampering apparently resolved the overheating problem for now.
>
> Next up: What's causing the engine missing, which is especially heard at
> around 1900 rpms shortly after the engine's warmed up.
>
>
> Best Regards,
>
> Randy
> #249 Simple Gifts
> Seattle/Bellingham
>
>
> &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
>
> 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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