Leaking heat exchanger?

[Balbas]

I've pulled the heat exchanger stack out of the heat exchanger. I'm sure all heat exchanger stacks are a similar design - this is a series of tubes sheathed (in copper?) and with an end cap at each end keeping the whole together. The sheathing doesn't cover the whole stack, there's about an inch at the front end of the stack where the tubes are exposed.

The whole lot was filled with muck and grunge, so I've cleaned it as effectively as I can. In doing so, I was running hot water into the tube nest - between the tubes and the sheathing. And I noticed that the sheathing has some small leaks. The tubes themselves don't appear to be leaking, just the sheathing. Am I safe to assume that this is fine and that the end cap design (together with a new o-ring) should prevent coolant water from being in this part of the heat exchanger?


Its an old Vetus M4.14 if that makes a difference.

And apologies for the numpty question. Just typing it out has helped me clarify in my own mind, but I'd like another opinion before I put it all back together.

 

[skipper021]

I've pulled the heat exchanger stack out of the heat exchanger. I'm sure all heat exchanger stacks are a similar design - this is a series of tubes sheathed (in copper?) and with an end cap at each end keeping the whole together. The sheathing doesn't cover the whole stack, there's about an inch at the front end of the stack where the tubes are exposed.

The whole lot was filled with muck and grunge, so I've cleaned it as effectively as I can. In doing so, I was running hot water into the tube nest - between the tubes and the sheathing. And I noticed that the sheathing has some small leaks. The tubes themselves don't appear to be leaking, just the sheathing. Am I safe to assume that this is fine and that the end cap design (together with a new o-ring) should prevent coolant water from being in this part of the heat exchanger?


Its an old Vetus M4.14 if that makes a difference.

And apologies for the numpty question. Just typing it out has helped me clarify in my own mind, but I'd like another opinion before I put it all back together.

It sounds like this stack needs a really good clean and pressure test to ensure it's going to work properly on restart.
I see you may be based in South Devon - You could try these people who carry out precisely this task for many marine engineers in the south west, often on some big power boat or military heat exchangers: http://www.heatexchangers.com/ They are based at Callington near Saltash.

Alternatively, you could bring the bits to Pilkington Marine at Newton Abbot, or Mountbatten Boathouse in Plymouth, they are both Vetus dealers and can supply new parts, but if this heat exchanger has been clogged up they will probably send it off to the guys at Callington.

I hope this is some help

 

[PCUK]

Do you mean tne sheathing is a cover over the tubes? If so it will not affect the integrity of the tubes so once all cleaned it should be OK to refit.

 

[Balbas]

It sounds like this stack needs a really good clean and pressure test to ensure it's going to work properly on restart.
I see you may be based in South Devon - You could try these people who carry out precisely this task for many marine engineers in the south west, often on some big power boat or military heat exchangers: http://www.heatexchangers.com/ They are based at Callington near Saltash.

Alternatively, you could bring the bits to Pilkington Marine at Newton Abbot, or Mountbatten Boathouse in Plymouth, they are both Vetus dealers and can supply new parts, but if this heat exchanger has been clogged up they will probably send it off to the guys at Callington.

I hope this is some help

That's really useful thanks. I've put it back together for the time being, but I'm not convinced the heat exchanger isn't porous, so I'll keep an eye on it. I'll also call the callington fellas tomorrow to ask for their advice. I'm thinking if I can coax it through another season I may ask them to look at it over next winter.

 

[Balbas]

Do you mean tne sheathing is a cover over the tubes? If so it will not affect the integrity of the tubes so once all cleaned it should be OK to refit.

Thanks, pretty much as I thought, so I've put it back together.

 

[Plum]

That's really useful thanks. I've put it back together for the time being, but I'm not convinced the heat exchanger isn't porous, so I'll keep an eye on it. I'll also call the callington fellas tomorrow to ask for their advice. I'm thinking if I can coax it through another season I may ask them to look at it over next winter.

Recommend you make yourself a coolant system pressure tester. Use a spare/old coolant filler cap and fit a tube to it that leads to both a pressure gauge and a car tyre valve. Put a bicycle pump on the tyre valve, pump up to, say, 15 psi and see how long it takes for the pressure to reduce. This will give you peace of mind whenever you are in doubt about your cooling system, or help you find most leaks. A good investment. Something like this https://drive.google.com/file/d/0B2pXHbT6ZkK0cHdHYl9pMjVSaG8/view?usp=drivesdk

Www.solocoastalsailing.co.uk

 

[Balbas]

It sounds like this stack needs a really good clean and pressure test to ensure it's going to work properly on restart.
I see you may be based in South Devon - You could try these people who carry out precisely this task for many marine engineers in the south west, often on some big power boat or military heat exchangers: http://www.heatexchangers.com/ They are based at Callington near Saltash.

Alternatively, you could bring the bits to Pilkington Marine at Newton Abbot, or Mountbatten Boathouse in Plymouth, they are both Vetus dealers and can supply new parts, but if this heat exchanger has been clogged up they will probably send it off to the guys at Callington.

I hope this is some help

Whilst the base engine is a reliable old donk, everything I've ever read about the marinisation of these motors isn't good reading. And it's obvious from the way the cooling circuit has been configured that there have been problems in the past. So, after sleeping on it, I called the guys in Callington today and had a chat.

As soon as I've got the boat back to the mooring I'm going to pull the whole heat exchanger and get it up to them for a pressure test. After a decent length chat on the phone discussing possible scenarios I'm confident that essentially they can fix whatever problems I may have and at the same time sort some of the issues that these heat exchangers are known for. Ok won't be super cheap, but considering a new heat exchanger from Vetus is £1,200... and anyway, what price reliability?

Thanks for the recommendation.

 

[Balbas]

An update to this thread. I pulled the heat exchanger and took it up to Callington. Many problems were discovered:-

• The end caps / bonnets weren't sealing correctly
• Inspite of my cleaning the whole thing was still minging
• Previous leakage had eaten away at the casing around the bonnets
• The stack itself failed a pressure test, it turns out there was no solder holding the tubes to the ends
• The jacket around the tubes was incorrectly positioned, which meant that the efficiency was severely compromised

Remedial action which has been taken is:-

• The whole thing has been shotblasted, chemically cleaned and (where appropriate) primed.
• The casing has been built back up with solder and then machined back down to the correct size. Fatter O-rings have been prescribed to provide a better seal. I will of course be using new copper washers for the bolts.
• The tubes have all been resoldered and pressure tested to 20psi.
• The jacket has been soldered in place, ensuring that the engine coolant is able to circulate correctly around the seawater tube stack.

I now have it back, fixed. Next steps will be to repaint the heat exchanger (assuming I can get some Vetus Orange paint in time, if not it'll be the closest match I can find in Halfords) flush the engine as best I can with fresh water and then to refit and test the heat exchanger.

I can't recommend the guys at SouthWest Heat Exchangers highly enough.

 

[Plum]

I have used the yellow hammerite smooth paint over their special metals primer. Not a perfect match to the Vetus colour but has certainly been very durable.

www.solocoastalsailing.co.uk

 

[Balbas]

I have used the yellow hammerite smooth paint over their special metals primer. Not a perfect match to the Vetus colour but has certainly been very durable.

www.solocoastalsailing.co.uk

good advice, thanks. Perfect colour match isn't important - it lives in the engine bay where the wife never looks!

 

[Balbas]

good advice, thanks. Perfect colour match isn't important - it lives in the engine bay where the wife never looks!

Struggling to find the right paint. Is there any reason I can't use brake caliper paint on my (primed) ally heat exchanger?

Calipers can get pretty hot, so I'm guessing it'll resist the temperature.

 

[Balbas]

I used Hammerite smooth in the end. Not a colour match, but doesn't matter.

So, update to the thread - I had the engine running for approx 7 hours this weekend motorsailing in light winds. And she's absolutely tickety boo - I can't speak highly enough of SouthWest Heat Exchangers. It's also a reminder that all is not lost when having problems. Vetus wanted £1,200 for a new heat exchanger. I paid a *lot* less than that to have mine fixed - and frankly I'd rather put the balance towards a new engine. If I can keep this one running for a few years longer and keep putting money away, when the inevitable day comes hopefully it won't be the shock it otherwise would be.