Re: Volvo MD11c - Cooling problem

Great that you know it is not the cylinder blocks blocked. Mine were really
difficult to clean even after disassembly and involved chisels and chipping
(chemicals were not really effective until most of the crud was mechanically
removed) I am surprised that you have sludge in the clean side of the
closed cooling circuit. Can you actually see the surfaces on both sides of
the heat exchanger tubes? Even if water runs through easily it doesn't mean
that the surfaces are not dirty enough to prevent heat transfer. I am not
familiar with HE fitted to boats but many industrial ones can be cleaned
mechanically inside and outside of the tubes. Don't assume that the "clean
side" doesn't get fouled. he only way to really tell is to measure the flow
and exit temperatures of the "seawater" and "engine" sides of the heat
exchanger. A cheap K type thermocouple thermometer is a convenient way of
doing this and will definitely indicate where the problem lies. I gave up
trying to discover the specified flow rate from Volvo.
Suppose your 1 gallon / min was raised through 20 deg f that would be 10lb x
20deg = 200 Btu per min. 1 hp = 42.4 Btu/min so that would be about 5hp
going to cooling. i.e. about 20% of your engine's maximum output. so it may
not be an unreasonable flow rate.

I suspect however that the most important consideration for CW flow rate is
to have sufficient to cause turbulence and distribute the water through all
waterways to help prevent hotspots and solids settling.

ChrisR

"travis" <travisbored@xxxxxxxxx> wrote in message
news:1155442926.458012.142630@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Good News! I swapped a few hoses around and took the heat exchanger out
of the system and now I am running too cool. I am not even moving the
temp. needle . I'll put the thermostat back in tomorrow.. although I'm
not sure how it lets seawater past the thermostat to cool the exhaust
if the thermostat has not yet opened but I'll figure it out tomorrow.

I took the end off the 'Sendure" heat exchanger and everything looks
very clean, all the tubes in the core were clear and running a garden
hose though all the ports there didn't appear to be any restrictions.
I think there must be some problem with that seawater pump. I'm now
using the other pump that was previously pumping engine coolant.

I paid 50 dollars CDN (35 Euro, 24 GBP) for the thermostat (which
didn't fit either), anyone know what that would cost in the UK?

Thanks for everyone's help.


Travis






Martin wrote:
On 12 Aug 2006 09:53:46 -0700, travisbored@xxxxxxxxx wrote:

Hi, Thanks for the quick replies.
I replaced the cam when I replaced the seals between the two stacked
(yet isolated) impellers. This was after the overheating problem and
made no noticeable difference. The two pumps are identical except for
this 'cam' One cam was half the thickness. I can only guess that it
was to provide more flow for either the seawater system or the coolant
(I can't remember which had the thicker 'cam'). I really wish I knew
how much water each pump should be moving.. as a gallon/minute seems a
bit low. .

As for the sludge, I believe there was some, I moved it aside by
sticking a thin wire though the pet*** to drain the coolant.

I have three drain plugs on my MD2B.


Perhaps I should be trying to run something else though the coolant
system to break down the rust and sludge?

Starbright make a product for doing this. I haven't used it but others
on Internet have and claimed good results.

Looking at the engine, I can't imagine taking the cyclinders apart to
clean the water jackets. I can only assume I'd find seized head bolts
or worse. Everyone keeps telling me how expensive the rebuild kits and
gaskets are. (here in Toronto at least)

Running the engine without the thermostat I would assume would keep it
around 140 or lower... instead It heats right up to near boiling,
perhaps past boiling point. But the seawater remains only luke warm.
I am considering running seawater though the water jackets and remove
the heat exchanger alltogether even if only to diagnose the problem
further. (I am in fresh water)

Has your boat spent it's life in fresh water? Is it possible that
there is a piece of an impeller blocking the flow somewhere?
--

Martin



.