Help! Leaking heat exchanger? Volvo Penta MD2020B.

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annalucidon

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Help! We have a problem with a Volvo Penta MD2030B engine (in a newly-bought 1993 Dufour sailboat with a saildrive). The engine is freshwater cooled via a heat exchanger using saltwater and we recently started taking on salt water. On investigating, the fresh water system was completely overrun by salt water. The engine really doesn't seem to be overheating, but we realised our bilges were full of a lovely coolant/salt water mix... The engine has an expansion tank, which is listed in the Owner's Manual as extra and which some people are telling us isn't neccessary for this engine i.e. we could just pour the coolant/water mix in through the filler cap and do away with the separate expansion tank - this where the water was actually coming from, but guessing this is simply because the expansion tank's seal was a weak point.

Taking advice, we have taken apart and thoroughly cleaned the insert (or "core") of the heat exchanger and throughly flushed the system through - it was indeed shockingly dirty and filled with **** (including pieces of old impeller) and we really hoped this was the problem - it certainly looked dirty and blocked enough to have been letting salt water into the fresh water system. (Does this sound right)?

We got the insert very clean and it didn't appear to have any leaks. BUT on running the engine, we still have the problem. The fresh water system is filling up with salt water. Please please please can anyone offer any advice? The heat exchanger core really didn't seem to be have a leak when we tested it, but people are telling us we need to buy a new one (sooo much money) and if there is a split in one of its pipes, it must be very small. Would this explain the significant volume of sea water infiltrating? I'm just not sure there isn't another problem somewhere.
 
I don't know this engine specifically but I understand that the heat exchanger sealing between the raw water and fresh water sides is a little tricky to set up correctly. Assuming that you have done this properly, here are some pointers. Under ideal operating conditions the pressure on the fresh water side is controlled by the pressure cap, maybe 12 psi? Pressure on the raw water side is nominally atmospheric or only a little higher, as it is open at the exhaust end. Thus it is not possible for seawater to enter the engine's cooling system if everything is correct, even if a cooler tube was leaking. So these facts suggest a few possibilities:

1. The pressure cap is not functioning for one reason or another. The expansion tank is there to catch overflow that passes the pressure cap, normally only due to thermal expansion, so not very much volume. If water is flowing from the expansion tank it suggests that the cap may not be doing its job. Try a new one.

2. Raw water pressure higher than correct fresh water pressure can only occur if its discharge to the exhaust is partially blocked. I suggest you check the exhaust manifold for salt accumulations internally, check the hose for any blockage and check the exit nozzle from the heat exchanger for anything blocking it inside. The raw water pump, being a positive displacement type, will deliver a very high maximum pressure if its discharge is blocked. However, its impeller is only rubber and there is a limit, so blades will fracture if you continue to operate it at high pressure.

I recall a thread on this, or a similar subject about a month ago. Might be worth searching.
 
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This is a bit of a mystery isn't it!!!!!
I don't understand the overflow of water except that if the salt water is continually topping up what should be the fresh water tank .....overflow would result once the system heated up even if the pressure cap was ok. The fact that there was coolant in the overflow suggests that there is two-way traffic from a leak in the tubestack.

You probably know this already but ASAP supply replacement heat exchanger tubestacks here:

http://www.asap-supplies.com/search/heat+exchanger/bowman-tubestacks

You can run a pressure test on the tubestack with an air line or foot pump.
If that's ok then the fault may lie with the rubber end caps which may not clamp perfectly if they are at all stretched.
Good luck!!
 
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You seem unceratin whether you have a 2030 or 2020 !

However THIS ONE
or
THIS ONE

And also the optional extra
EXPANSION TANK

The problem with your salt water ingress into the freshwater coolant is almost certainly due to a leak between one of the rubber end caps and the tube bundle

Tighten the smaller hose clips #4 but if the leak persists inspect the end caps for damage as well as rechecking the tubes for leaks

If you do away with the expansion tank then you loose the benefit of the level sensor that goes with it .
( I assume I have correctly identified the expansion tank ... )
 
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Also:

Take note of what Vyv says about possible obsruction to the saltwater flow downstream from the heat exchanger
 
I have a 2020B.

IMHO if the copper heat exchanger tubes are intact and fitted the right way up, then it is almost certainly the rubber end caps either failed or incorrectly fitted.
It is a simple arrangement and there is virtually no other way sea water can get into the fresh water/coolant.
 
Had the very same problem earlier this summer with our MD2040D (on a Dufour 385). The heat exchanger set up is essentially identical to yours.

When it first happened we lost all of the coolant in a relatively short space of time. I normally quickly visually check motor every hour or so when motoring. On one check everything OK , next check about 5 litres of bright green coolant under motor!! The smaller of the jubilee clips on the rubber end caps were not as tight as they should be and heat exchanger stack was partially "furred" up. Also injection point into exhaust elbow was partially blocked. Both cleaned and heat exchanger checked for leakage (no leaks), reassembled, system flushed through with fresh water and refilled with antifreeze. All apparently OK but after a few days I noticed a very slight leakage from the coolant tank overflow again. Not major, but clearly salt water was getting into the freshwater system.

Dismantled again, flushed and reassembled taking great care to ensure that the heat exchanger stack protrudes by an equal amount at both ends . If you push the stack right into the rubber cap at the exhaust end as far as it goes you have gone too far.... and there will be insufficient protruding at the front end to get a decent grip with the front jubilee clip. (ideally the heat exchanger stack could usefully be 10-15 mm longer!)

Since then, all is now OK. From talking to many others, whilst this is not an everyday problem, it's not that uncommon either!!

Hope this helps.
Dave
 
annalucidon said:
Help! We have a problem with a Volvo Penta MD2030B engine (in a newly-bought 1993 Dufour sailboat with a saildrive). The engine is freshwater cooled via a heat exchanger using saltwater and we recently started taking on salt water. On investigating, the fresh water system was completely overrun by salt water. The engine really doesn't seem to be overheating, but we realised our bilges were full of a lovely coolant/salt water mix... The engine has an expansion tank, which is listed in the Owner's Manual as extra and which some people are telling us isn't neccessary for this engine i.e. we could just pour the coolant/water mix in through the filler cap and do away with the separate expansion tank - this where the water was actually coming from, but guessing this is simply because the expansion tank's seal was a weak point.

Taking advice, we have taken apart and thoroughly cleaned the insert (or "core") of the heat exchanger and throughly flushed the system through - it was indeed shockingly dirty and filled with **** (including pieces of old impeller) and we really hoped this was the problem - it certainly looked dirty and blocked enough to have been letting salt water into the fresh water system. (Does this sound right)?

We got the insert very clean and it didn't appear to have any leaks. BUT on running the engine, we still have the problem. The fresh water system is filling up with salt water. Please please please can anyone offer any advice? The heat exchanger core really didn't seem to be have a leak when we tested it, but people are telling us we need to buy a new one (sooo much money) and if there is a split in one of its pipes, it must be very small. Would this explain the significant volume of sea water infiltrating? I'm just not sure there isn't another problem somewhere.
Click to expand...
Vyv is quite right about the injection elbow getting blocked, if it does then the raw water could get enough pressure to get past the top hat rubbers at each end of the stack. It is something that does happen eventually on the 2030!!
Stu
 
I had a similar problem on the Perkins version(before they were marketed as the 2020/2030 by VP) renewed both the end caps, cleaned out the heat exchanger, carefully refitted it so the rubber end caps were securely clipped(I used new jubilee clips) and had no further trouble.
Later I also had to replace the water injection elbow when it wouldn't rev under power and found the outlet reduced to about a 10mm diameter hole and my screwdriver went through the cating when trying to chip it clean. Incidently the VP part was cheaper than the Perkins part, identical apart from the colour! It was like a new engine afterwards.
 
The post a month or so ago was by me. Same or similar problem, the details are all here:http://www.ybw.com/forums/showthread.php?t=241350

You wills see that it was a combination of blocked exhaust injection elbow and poorly fitting rubber end covers on the heat exchanger.

If you are worried about your heat exchanger stack, I still have the rig that we built to test mine in the air engineering workshops at work. Drop in and we could test it for you.

The exhaust de-blocking saga was in a thread here:http://www.ybw.com/forums/showthread.php?t=241849
 
Huge thanks: your responses are invaluable and massively appreciated.

Lsjaboardceltic is my mom and the boat is hers - I've just returned back from her to the UK (she's in Sardinia) and posted on her behalf, because her internet access is limited (and because this problem has been so darned frustrating!).

All instincts are that the fit of the rubber muffs/end caps may be to blame, and we definitely need to investigate further cleaning of the exhaust elbow.

Thank you once again for your time and help. (And it's MD2030B! Apologies for confusion)
 
Exhaust elbow & heat exchanger thanks to everyone

From Annalucidon & lsjaboardceltic:

A million thanks everyone.
The elbow & its small plugs were blocked causing the salt to mix with fresh water so ther expansion tank seriously leaked. Also the rediator cap was salted up & the cap's rubber grommet had disintegrated.

Hydrochloric acid cleaned the elbow on the pontoon. Volspec were very helpful too. Id been told the elbow only lasts 5 yrs by a so called mechanic here in Cagliari. Its clean now. I went to the expense of a new heat exchanger core stack too as it looked very very warn. New caps & new expansion tank have fixed it.

Thank you all for your help.
 
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