MD22 Diesel Heat Exchanger problems

boatone

boatone

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Just a few cables from Boulters Lock
www.tmba.org.uk
Does anyone have personal knowledge of this engine?
I have water crossing over from the raw water side and causing the coolant side to expel water through the pressure cap relief hose. This suggests either a sealing problem or possibly a leak in the heat exchanger tubes.
Any first hand knowledge would be appreciated.
 
It depends which version of the engine but if your heat exchanger has the big rubber end caps #5 in the diagram below then you problem may simply be that one of them is not sealing on the end of the tube nest, Try tightening the smaller of the two hose clips #6 at each end. ( not an uncommon problem and the second on the forum within a couple of weeks)

15871.jpg
 
Boatone,

I had the same problem on my MD22. Do you have a calorifier?
If so, have you considered the possibility of raw water inside the calorifier coil leaking into the fresh water, causing the excess water to be expelled from the pressure cap.. This was the cause of my problem, I had to replace the calorifier ( Cheaper than a new heat exchanger).

Isolating the calorifier, and running the engine with it disconnected will prove or disprove this theory.

Good luck, let me know the result.

Kind regards,

Steve.
 
I have a twin engine installation but the one with the problem does feed the calorifier.
However, I am at a loss to understand how domestic water in the calorifier could feed back into the engine coolant system. Wouldn't any excess pressure be vented by the calorifier PRV?
 
If it is salt water that is overflowing from the cooling system then its the heat exchanger that the trouble. Taste, but don't drink it if it still contains any antifreeze.

If it is salt water get it sorted and the cooling system well flushed and refilled with antifreeze mixture ASAP.
 
VicS said:
If it is salt water that is overflowing from the cooling system then its the heat exchanger that the trouble. Taste, but don't drink it if it still contains any antifreeze.

If it is salt water get it sorted and the cooling system well flushed and refilled with antifreeze mixture ASAP.
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Boat is based on the non tidal Thames so fresh water unfortunately but thanks for the advice.
 
boatone said:
Boat is based on the non tidal Thames so fresh water unfortunately but thanks for the advice.
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So how do you know it is raw water causing the prob?
Stu
PS if yours is the early one Vic is right, if its a later one then its a different system and it could just be O rings on the exchanger stack.
Stu
 
skipper_stu said:
So how do you know it is raw water causing the prob?
Stu
PS if yours is the early one Vic is right, if its a later one then its a different system and it could just be O rings on the exchanger stack.
Stu
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Because water is being expelled thru the pressure cap outlet but the level in the header tank remains the same same so it must be being replaced from somewhere and cant think any other option than the raw water side.

Not sure what you mean by 'earlier' or 'later' - its an TMD22A
 
boatone said:
Because water is being expelled thru the pressure cap outlet but the level in the header tank remains the same same so it must be being replaced from somewhere and cant think any other option than the raw water side.

Not sure what you mean by 'earlier' or 'later' - its an TMD22A
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If its the A, its the early one as in Vics diagram http://www.marinepartseurope.com/en/volvo-penta-explodedview-7744150-25-306.aspx
So water can pass across the rubber top hats.
However! The raw water pump pumps to an open end (the exhaust) so there shouldnt be much pressure there, I think the header tank cap opens at about 7psi, so where is the pressure coming from. Is the exhaust elbow blocked? In this case the raw water could build up pressure OR is the domestic calorifier pump, pumping water from the domestic circuit thru a broken heat exchanger? as has been suggested elsewhere
Stu
 
VicS said:
Now he tells us :) However has the rubber endcaps it seems
TAMD22A:-
Click to expand...
Thats the same diagram you posted in your initial reply, Vic, and is correct. That is the route I am now pursuing so inspecting the end caps etc will be my next step.

Incidentally, do shop around for best prices for spares. HIghest price I have come across for the end caps is £145 - lowest is £49 + vat - and they are the same volvo original part!
 
Not exactly the same drawing!

Is it possible to de-pressurise the domestic water system to eliminate that and a calorifier leak as a source of the water?

As Stu says for it to be raw water something must be causing the pressure in the raw water side of the heat exchanger to be greater than the coolant pressure, other wise you'd loose coolant.
 
I will look at the calorifier possibilities but although there is a pressure pump on the domestic water there is no accumulator and no evidence of the pump running other than when a tap is turned on and it stops once the tap is shut.

I am arranging for an engineer to carry out a pressure test on the header tank as a starter and will inspect the rubber caps etc and take it from there.
 
Just been reading up about calorifiers and hadn't realised just how much pressure is generated in the hot water tank.

Not sure what the PRV setting on mine is but with 1 bar = 14.5 psi its going to be well in excess of the 7psi cap on my header tank !

Will definitely be checking this out as it occurs to me that this problem has arisen since I first used the immersion heater on shore power a few weeks ago - may just be coincidence but ........
 
Hi Boatone,

Having had the same symptoms on my MD22 I think it most likely that the problem is in your calorifier. Even a pinprick hole in the heating coil will allow the freshwater pressure to be transmitted to your coolant system. As you point out, the freshwater pressure in your calorifier is greater than the relief pressure of the cap on your coolant header tank and hence the coolant overflow.

Putting a clamp on the calorifier coolant outlet pipe will quickly establish if this is the cause of your problem.

Regards,

Steve.
 
boatone said:
I will look at the calorifier possibilities but although there is a pressure pump on the domestic water there is no accumulator and no evidence of the pump running other than when a tap is turned on and it stops once the tap is shut.

I am arranging for an engineer to carry out a pressure test on the header tank as a starter and will inspect the rubber caps etc and take it from there.
Click to expand...
Having said what I have said, one of your points, the fresh water pump isnt running says that it isnt the calorifier, only other thing is the head gasket or the exhaust elbow is blocked
Stu
 
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