Mercruiser Heat Exchanger Tank Repair Advice (30 year old family boat...)

Every other year the solder holding the glycol tank onto the heat exchanger tank corrodes out and I get a glycol leak. The tank has been resoldered several times by the radiator shop but the solder always seems to crack or corrode out, although the tank metal (brass?) seems to be ok.

A new heat exchanger is about C$1000 or more so there is a big incentive to resolder it.

The glycol tank is like the upper section of a car radiator, the lower tank is a heavy brass (?) cylinder containing copper tubes carrying seawater through the glycol found in the cylinder and the upper tank. There is an anode in the seawater side but no anode in the glycol side that corrodes out. The part that corrodes isn't even in contact with salt water.

I think that part of the problem is that the solder cannot hold as the joint between the two cylindrical tanks appears to be a simple solder butt joint covered by a fillet (there may be a flange on the glycol tank edge hidden by the solder fillet). Either that or the radiator shop is not using the right type of solder.

I'd like to reinforce the joint with a doubling strip of formed metal but I'm not sure what type of metal would match the tank (Copper, Brass, Bronze?) or what type of solder would be best to resist corrosion (60/40, Silver Solder etc.)

Any radiator soldering wizards on the planet with tricks of the trade in resoldering these kinds of things?

Thanks, Graham

Reply to
Graham Parkinson
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I don't know what diameters with which you are dealing. What about a water main repair coupling?

It was really hard to find a picture of what I had in mind:

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(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens)

Reply to

While you may be seeing corrosion, I would be more inclined to suspect you are getting a resonance with engine vibration that is cracking the joint. Solder does not usually corrode. You might want to consider putting a stiffener of some sort on the system so the joint is not at a point that gets any loading on it. All that really should be on the joint is the pressure which is less than 15 psi max and in reality is probably very close to normal atmospheric pressure since they tend to run the engines with a 160 degree F or thereabouts thermostat (too hot and you start precipitating the salt out of solution in the heat exchanger and plugging it up). My guess is on a vibration related issue -- you should see the damage resonance can do --- ever see the pictures of the Tacoma Narrows bridge when it blew down ???


Reply to
Mike Fields

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