[C38] Overheating issue

[Michael de lisle]

Thank you for your input guys. My boat is hull #240 and has the Universal
M3 (5424) diesel. I just installed a brand new raw water pump two months
ago and had plenty of flow in the exhaust exiting the boat. I thought about
a blown head gasket but there is nothing mixing with the oil to indicate
that this is the issue. As for the bracket, I am taking it to a very
reputable welding/fabrication shop here and having them fab up a new one
that will be a bit beefier. And I can not afford a new exchanger just yet
but will be upgrading to the three inch when I do. How is your plumbing for
the hot water tank mounted? Mine was strapped to the exchanger with a
couple of radiator hose clamps.

On Fri, Jul 11, 2014 at 10:02 AM, Max Soto <maxsoto at gmail.com> wrote:

> The heat exchanger is definitely not good enough for the 5424, but if it
> has been working for some years, and suddenly the engine overheats like
> that, that is weird.
> The engine could run perfectly without a thermostat. Mine has been like
> that for more than twelve years.
> An air bubble might be the issue, but is weird that it develops out of the
> sudden, since it usually happens when you are filling an empty engine with
> coolant.
> You haven't mentioned anything about the raw water system.. Is it working
> as it should???
> A blown head gasket should be taken in consideration.  A compression test
> will tell the truth.  And also, a  very bad coolant cap failure might have
> some effect like that
>
> Just my two cents!
> Max Soto
> +506-8312-1367
> Alajuela, Costa Rica
>
> > On 10/07/2014, at 22:36, Michael de lisle <krazymiked at gmail.com> wrote:
> >
> > So I am completely stumped and need your input.
> >
> > This all started when my boat overheated and boiled off all the water in
> the manifold filling the cabin with white smoke (steam). We got her back to
> the dock under sail and my initial thought was a plugged heat exchanger. On
> the trip back I had pulled the thermostat to check it and gave it the boil
> test where everything worked as it should. As a precaution I left the
> thermostat out to let the engine run cool but it was still getting hot.
> >
> >  When we got back to the dock and with the fresh water circuit still in
> tack I opened the bleed off valves and noticed that the fresh water I had
> added to the manifold was not mixing with the coolant at the bottom bleed
> off valve.
> >
> > When I got down inside I found the valves for the hot water tank
> strapped to the heat exchanger (HX) and the bracket that supports the HX
> snapped off at the bolts and the whole mess sitting atop the transmission
> housing.
> >
> > I pulled all the hoses and the HX plus hot water tank plumbing out and
> found that the HX was actually looking pretty good. I flushed the engine
> with the hoses removed and it was flowing through all the ports with out a
> problem. I soaked the HX overnight anyways in a mix of muriatic acid and
> water since I had it out and have yet to reinstall.
> >
> > When explaining all of this to my local mechanic he suggested that the
> likely problem was the fresh water pump mounted on the front of the engine.
> Tonight I pulled the the fresh water pump from the block and found
> absolutely no issues with it. No wobbles, no wear, no goop or corrosion.
> >
> > So whats the problem???
> >
> > Tomorrow I am taking the HX and the pump to the shop to have them
> inspected. I am also going to double check the block with a hose to make
> sure all the ports are open and free flowing. Once I get a new bracket
> fabricated I am reinstalling everything with new hoses.
> >
> > Has anyone got any advice as  where else I should maybe check before
> putting everything back together?
> >
> > I have not ruled out an air lock from low coolant in the system but
> won't know if that was the issue until reinstalling everything.
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