Sealant for heat exchanger

[xxxxx]

Your thermostat is set to 76degC so there shouldn't be much pressure in there.

The red high temperature permatex sealant is good >218psi. The blue water pump one good for 377psi. In the TDS sheets.

[Stu Jackson]

A superb alternative, and improvement over JBWeld is DEVCON. You can get it in small tubes, $13. It's a two part epoxy for metal.

[Niall leslie]

Now we have a better idea of the situation.
- Typical original pressure cap for the cooling system with Volvo's of that era was 8 PSI however there may be an aftermarket cap fitted and while most range from 5 to 10 PSI the occasional one goes as high as 15 PSI +-.
- I can second the good comments about Devcon epoxy for that type of thing.
- Possible try to enlist help from someone who has experience if there is any one around.
- The impression given is that there is severe corrosion that will require build up on sound metal after filing away the corrosion and then sealing with silicone on assembly. If so make sure that the epoxy compound chosen has a good mechanical key and that the surfaces are completely clean ( in a pinch acetone will generally work well for cleaning. ) The epoxy can be "overbuilt" then hand shaped to suit using files etc.and just taking the necessary time + being careful. threads can be cut in the epoxy compound such as Devcon if needed quite simply with the normal drills and taps.

Once all of that has been done then the epoxy can be allowed to fully cure before assembly using appropriate RTV silicone. Be careful not to apply too much silicone and then give the silicone 24 hours to cure before testing etc.

For any threaded holes ( female thread ) that have failed or are "iffy" then you could take the appropriate helecoil kit(s) with you and install the SS inserts for a permanent repair. gaskets can be easily made from the appropriate gasket material using common tools.

The biggest issue is likely your lack of practical experience as evidenced by your having to ask for opinions instead of just deciding on what is the best way to do the repair and then just getting on with it. That's not easy to replicate although it is likely not a hugely complicated job. Just take your time and make sure that you minimize any mistakes. Possibly try several things at home first as practice - corroded items can be easily obtained from scrap yards.

Good luck,

Niall.

[s/v Jedi]

Originally Posted by Cheechako

DON'T use JB Weld. Been there tried that. The JB became soft and pliable leaking within 15 minutes of running the engine. I used it on a cracked fitting on top of a coolant tank. Evidently it doesn't like heat. Maybe just filling some pits it would work...?

No, that can’t be right, something must have been wrong. The heat exchanger doesn’t get much higher than 200F and JB Weld is rated to 550F and used by many to fix engine parts that get hotter than a heat exchanger.

(what kind of JB Weld was used, how old was it? How long cured etc.)

[Checkswrecks]

Originally Posted by s/v Jedi

No, that can’t be right, something must have been wrong. The heat exchanger doesn’t get much higher than 200F and JB Weld is rated to 550F and used by many to fix engine parts that get hotter than a heat exchanger.

(what kind of JB Weld was used, how old was it? How long cured etc.)

I'm going to agree and guess that the JB Weld had been compromised by age or other contaminates. I've personally known it to work on metal radiators IF IF IF the metal was sanded and really clean AND the JB weld was put on fairly thick. Engine oil temps are frequently in the 250+F area and JBWeld has been used countless times all over the world to fix oil pans and crank cases, which get hotter than a HX.

[Cheechako]

Originally Posted by Checkswrecks

I'm going to agree and guess that the JB Weld had been compromised by age or other contaminates. I've personally known it to work on metal radiators IF IF IF the metal was sanded and really clean AND the JB weld was put on fairly thick. Engine oil temps are frequently in the 250+F area and JBWeld has been used countless times all over the world to fix oil pans and crank cases, which get hotter than a HX.

Yeah hard to say I guess, but that's what happened. It definitely wasn't fresh JB Weld. Been aboard a year probably. I tried this repair in Trinidad while on the hard. Plenty of cure time. A large fillet build up around the fitting. The coolant tank was aluminum. I used it on a pulley that got pretty hot a couple months previous with no issues. Antifreeze issue maybe?

[Locquatious]

Hard epoxies cure to the point where molecular motion slows way down. This is when the curing epoxy reaches a glass transition temperature. If you warm the curing epoxy up, the glass transition temperature will also go up, usually achieving a little less than the temperature you warmed it to. If you continue to increase the temperature of cure, the epoxy will harden to its maximum glass transition temperature. That temperature is an inherent property of the epoxy. Typically the epoxy will be harder but more brittle when cured to the max. But it will keep its shape better up until the glass transition temperature.

You would want to avoid letting the epoxy get wet or absorb humidity while curing. So just after the epoxy has cured to a room temperature cure is the best time to raise the curing temperature. This approach allows you to keep the shape of epoxy you want during the cure.

[Newf1]

I used Marine-Tex epoxy to repair a corrosion issue on the heat exchanger on my 2014 VP D1-30. The consistency of the mixture was easy to work with and held in place on a vertical surface. It's held up for over 700hrs now. It may not work for your application but it's worth a look.