[C320-list] engine overheating

[Matt Curtis]

Thanks Jeff,
   
  I ended up removing the heat exchanger tube, the end caps for its housing, as well as the entire exhaust mixer and elbow unit.  I soaked everything overnight in CLR and got a lot of mineral deposits loostemned up.  The CLR discolored the metal slightly.  I also soaked everything in Coke overnight.  I then reinstalled everything, drained the rest of the coolant and refilled with fresh (the engine manual fails to point out that when you remove the heat exchanger, about 50% of your coolant pours out...everywhere!).  
   
  The engine was still running too hot.  I disconnected the raw water tube from the heat exchanger to see if I was getting full flow from the water pump...It was.  I then reconnected the tube, but disconnected it at the other end by the water pump.  I primed the tube with water and blew through it by mouth.  There was WAY too much back pressure.  I kept the pressure on and eventually blew whatever it was out.  I then repeated the process until there was normal resistance.
   
  The engine ran fine after this, so I waited until it was warm and tapped the exhaust manifold and some otrher components of the cooling system with a hammer to loosten anything else inside while the water was flowing through.  Hopfefuly this prevents a recurrence of this anytime soon.

  I do not know what the small linear gaskets are for - it may be to help keep the tube in place and keep it from rotating while it is in the housing.  The engine manual says to replace the gaskets when the tube is removed, but I didn't have a second set.  I'll order some and replace them next time I change the coolant.  Upon inspection, the rubber on all the gaskets appeared fine.
   
  -Matt
  
catalina at thehares.com wrote:
  
Hi Matt,

All the responses so far are good info.

Our raw water pump developed a leak where the pulley shaft enters the
impeller area. We have the Johnson pump, and it has a little $2 rubber
bushing that forms this seal that could be pulled out with needle nose
pliers and replaced to stop the leak. Your hull has a slightly different
pump, but you may still have a similar rubber seal that can be replaced.

The raw water heat exchanger is a topic that hasn't been discussed much
here. This year, I removed the 4 nuts holding that cover in place and
took a look to see what condition the exchanger was in. To my surprise, I
saw a portion of a leaf laying across a few of the tube intakes. If you
had any blades of an impeller break off, they'd be in there too as the
cooling tubes are too small for much debris to go through.

Something I didn't fully understand was that there is a rubber gasket on
the cover that divides the tubes into 2 sections at rougly 60/40 with the
raw water entering the smaller section. Since the outlet is at the back,
it seems that 60% of the tubes don't get water flowing through them for
cooling?

Perhaps, this is a way to allow the engine to be used in different
applications with different temperatures of cooling water available simply
by supplying a different front inlet cap?

Anyway, this makes it seem like any debris in the smaller chamber could
have a serious effect on the heat exchanger's ability to do its job. If
you haven't removed this cover before, it's simple. No springs or ball
bearings are poised to shower your cabin and the amount of water in
there is very small. Also, this doesn't open up into the antifreeze
loop, just the raw water loop, so it's a simple procedure.

Cheers!
-Jeff


> Hi, This past Sunday, the engine was running hot and eventually the temp
> alarm atarted sounding. I shut her down and waited to open the engine
> hatch.

> I noticed a little bit of water seeping out from under the forward
> engine compartment hatch, and when I looked, I could not identify where
> it came from.
>
> I troubleshooted from the raw water inlet to the water pump - all is
> fine. Should my next step be to look at the mixing elbow? I've read
> that deposits can build up, leading to less flow and ultimatley
> overheating.
>
> I'm worried because thw elbow is covered in heavy duty Al foil,
> presumably because the previous owner found or assumed a leak...I'm
> scared as to what I might find!
>
> Any thoughts/tips/ideas?
>
> Thanks!
>
> Matt Curtis
> Tortuga, #541





Matthew Curtis
mcurtis_6775 at yahoo.com