Heat exchanger repair

MagicalArmchair said:
Which puts me square back on your first idea @jwfrary of trying to get someone to braze it to build it up. The alternative is getting it machined down flat by removing the studs and getting the surface lapped (if there is enough flange left to facilitate that!). See below, the bottom is the most eaten away.

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The quoted temp figures are for exhaust gases, not the heat exchanger. The whole assembly is being sea water cooled and will not be at those temps.

That said, looking at the latest pic (which should have been the first pic), i would not attempt to repair that with epoxy. That needs to be removed and repaired professionally.
 
PaulRainbow said:
The quoted temp figures are for exhaust gases, not the heat exchanger. The whole assembly is being sea water cooled and will not be at those temps.

That said, looking at the latest pic (which should have been the first pic), i would not attempt to repair that with epoxy. That needs to be removed and repaired professionally.
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Agreed, it wont be quite at those temps, but I think its likely to exceed the capabilities of epoxy!
 
Thanks Bob, I'll retreat from that approach - how did you fix yours in the end? I've sent five emails to five different specialist welding firms locally - hopefully someone can make this good.

The alternative is what this poor hapless soul ended up doing: 2002 Bavaria 38 - Volvo Penta D2-55A - replacing heat exchanger

It seems a terrible waste of materials to bin the whole heat exchanger body for the sake of a few millimeters off the flange.

As ever, thanks everyone for the assistance and collective wisdom. (y)
 
MagicalArmchair said:
Thanks Bob, I'll retreat from that approach - how did you fix yours in the end? I've sent five emails to five different specialist welding firms locally - hopefully someone can make this good.

The alternative is what this poor hapless soul ended up doing: 2002 Bavaria 38 - Volvo Penta D2-55A - replacing heat exchanger

It seems a terrible waste of materials to bin the whole heat exchanger body for the sake of a few millimeters off the flange.

As ever, thanks everyone for the assistance and collective wisdom. (y)
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By replacing the engine with a Beta. Once I started stripping my engine back, I found the entire heat exchanger and aftercooler stack was corroded and the cost of replacement was more than a new engine, so on the basis that my engine had done quite a lot of hours and was getting a bit tired, I decided to bite the bullet and replace it.

I would suggest that you take the heat exchanger off and get it apart. You can then have a really good look at it to see if there there is corrosion anywhere else. If it just this flange, then I would take it to a radiator specialist and ask them if they can either build the flange up or machine it back and weld a new one on. You then should have it pressure tested to make sure that there aren't any pin-hole leaks. As the walls get thinner, they start to bleed coolant into the raw water, which really spells the beginning of the end.

Sorry to be the bearer of bad news, but it's not worth bodging.
 
Bobc said:
By replacing the engine with a Beta. Once I started stripping my engine back, I found the entire heat exchanger and aftercooler stack was corroded and the cost of replacement was more than a new engine, so on the basis that my engine had done quite a lot of hours and was getting a bit tired, I decided to bite the bullet and replace it.

I would suggest that you take the heat exchanger off and get it apart. You can then have a really good look at it to see if there there is corrosion anywhere else. If it just this flange, then I would take it to a radiator specialist and ask them if they can either build the flange up or machine it back and weld a new one on. You then should have it pressure tested to make sure that there aren't any pin-hole leaks. As the walls get thinner, they start to bleed coolant into the raw water, which really spells the beginning of the end.

Sorry to be the bearer of bad news, but it's not worth bodging.
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Very interesting (and slightly depressing :D). I had noted I was losing coolant, I presumed it was from the rubber insert in the cap on top of the exchanger - lets hope it pressure tests up okay. I will get it off tomorrow and take it apart.

How do you pressure test the unit once all cleaned up?
 
MagicalArmchair said:
Very interesting (and slightly depressing :D). I had noted I was losing coolant, I presumed it was from the rubber insert in the cap on top of the exchanger - lets hope it pressure tests up okay. I will get it off tomorrow and take it apart.

How do you pressure test the unit once all cleaned up?
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You basically block all the holes up and then pressurize it with an airline and then leave it for a day to see if it holds the pressure. A radiator specialist will be able to do this for you.
 
Thank you all, I've had some cracking responses from local engineering outfits that specialise in aluminium welding stuff, so that at least is good news.

Do I get it pressure tested FIRST before getting the flange sorted? Else having the flange sorted and it leaking will still leave me with a busted heat exchanger and a tasty bill?
 
A place where they commonly start to go thin and leak coolant is just inside that exhaust flange, where the material has gone. Give it a good hard poke with a screwdriver to make sure that's not on the verge of going through before spending time and money on it.
 
MagicalArmchair said:
Thank you all, I've had some cracking responses from local engineering outfits that specialise in this stuff, so that at least is good news.

Do I get it pressure tested FIRST before getting the flange sorted? Else having the flange sorted and it leaking will still leave me with a busted heat exchanger and a tasty bill?
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Yes.

First, get it apart and inspect it all
Next give it a good prod with screwdriver (especially around the exhaust port) to make sure there isn't anything just about to let go
Next get it pressure tested.

Only if all this is good, do you bother getting the flange sorted.
 
Rogershaw said:
Do consider to pressure ites it properly you will need to seal all flanges to allow pressure to build up including the damaged one.
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Not quite the case. You pressurise the coolant side of the tank, so block all the coolant inlet/outlets, and then pressurise it through what is basically a radiator cap with a schrader valve in it.
 
Bobc said:
Not quite the case. You pressurise the coolant side of the tank, so block all the coolant inlet/outlets, and then pressurise it through what is basically a radiator cap with a schrader valve in it.
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I it just a raw water/ fresh water heat exchanger or is it a heat exchanger and water cooled exhaust manifold combined

If it's the latter does the heat exchanger have chambers for the fresh waater, raw water and exhaust gasses.
 
Is my understanding of how this works correct in the below? Last boat was raw water cooled!

Raw water blue, Fresh water Red, Exhaust gases orange...?

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Quote from the lovely folk at French Marine for a new one - £2,500 ish - ho ho ho :D.
 
The coolant sits in the header tank and is pumped around the engine in a closed circuit. The raw water is pumped through the tube stack by the raw water impeller to cool the coolant. That's basically it.
 
Bobc said:
The coolant sits in the header tank and is pumped around the engine in a closed circuit. The raw water is pumped through the tube stack by the raw water impeller to cool the coolant. That's basically it.
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And what cools the exhaust gasses in the manifold fresh water or raw water
 
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