Heat exchanger repair

[superheat6k]

The heat exchanger is off! I didn't have the right four sided socket to undo the drain plug, assuming my standard sockets would suffice... no chance... so I whipped the pipe off the bottom of the fresh water pump and that proceeded to dump the coolant into the bilge under the engine perfectly well. I sucked that up with my little 12V electric pump, took off all the hoses, and unbolted the heat exchanger. Very simple indeed.

I next took it to the guys at Welding Services in Kent | Go To Engineering. They were the only solitary lights still on in the trading estate. We were greeted by a very tidy, clean and professional engineering shop. The engineer that (socially distantly) greeted me was very well informed and helpful, and explained everything to my eight year old boy, who had helped with getting the unit off. The engineer cleaned up the corrosion there and then, and to test if it was possible, tried welding a bit to build it up. He confirmed it would be no trouble to weld as they did lots of delicate aluminium stuff (as evidenced by the array of metal work around their shop).

We spoke about pressure testing, and we agreed that it would be fine to just pressure test the raw water cooled side, else we would need to make up lots of plates and gaskets etc. What PSI should he test it at I wonder? That unit above has 30psi written on it? Is there a psi that would damage it I wonder?

I would suggest 2 bar or 30 psi but not higher, or you could cause a further problem.

 

[rogerthebodger]

If you only pressure test the raw water side all yo are testing is the heat exchanger tube stack. The tube stack is not aluminum

You need to pressure test the fresh water side as that is where the aluminium could corrode.

The damage you have is in the exhaust outlet so I would test that part as well.

A big flat plate with a sheet of rubber G-clamped onto where the exhaust manifold and thermostat would block off most of the outlets.

On the pipe inlets/outlets you can fit a rubber pipe with a insertion bung worm clipped on would seal the test.

 

[Bobc]

If you only pressure test the raw water side all yo are testing is the heat exchanger tube stack. The tube stack is not aluminum

You need to pressure test the fresh water side as that is where the aluminium could corrode.

The damage you have is in the exhaust outlet so I would test that part as well.

A big flat plate with a sheet of rubber G-clamped onto where the exhaust manifold and thermostat would block off most of the outlets.

On the pipe inlets/outlets you can fit a rubber pipe with a insertion bung worm clipped on would seal the test.

Spot on. You MUST pressure test the coolant side. Testing the raw water side will tell you nothing.

 

[MagicalArmchair]

Thank you for alerting me to that - I have briefed the engineers to test both sides to 15psi and told him what needs to be 'blocked' up.

Let's assume all goes swimmingly, the port gets made flush, and it all pressure tests fine. To give it a good service of all of the three chambers...

1. Take out the tube stack and soak that guy in white vinegar overnight to clear it out.
2. Fill the chamber it sits it with white vinegar and leave that overnight too.
3. Rinse through the freshwater waterways. Anything else I should do with the freshwater side? It looks pretty clean, clear and good?
4. How do you get rid of the carbon in the exhaust airways? They are pretty clear, it would be good to remove all deposits though. Or is this a job for someone with a hot tank?
5. Replace all gaskets etc and reassemble.

On the paper gasket to the block, do you smear any small amount of copper slip or the like?

 

[garymalmgren]

On the paper gasket to the block, do you smear any small amount of copper slip or the like?

Considering your experience with corrosion up till now I would avoid anything that is conductive.
Grease or oil would be it for me.

As aｎ aside、 I am surprised that nobody has come aboard with the same corrosion problem.
Is yours an isolated case.?
If so why?

Merry Cristmas and happy New Year to all.
Looking forward to a better one next year.

gary

 

[Bobc]

I am surprised that nobody has come aboard with the same corrosion problem.
Is yours an isolated case.?
If so why?

Pretty much all VP engines suffer from this problem. It's what usually kills most of them.

 

[Bobc]

Thank you for alerting me to that - I have briefed the engineers to test both sides to 15psi and told him what needs to be 'blocked' up.

Let's assume all goes swimmingly, the port gets made flush, and it all pressure tests fine. To give it a good service of all of the three chambers...

1. Take out the tube stack and soak that guy in white vinegar overnight to clear it out.
2. Fill the chamber it sits it with white vinegar and leave that overnight too.
3. Rinse through the freshwater waterways. Anything else I should do with the freshwater side? It looks pretty clean, clear and good?
4. How do you get rid of the carbon in the exhaust airways? They are pretty clear, it would be good to remove all deposits though. Or is this a job for someone with a hot tank?
5. Replace all gaskets etc and reassemble.

On the paper gasket to the block, do you smear any small amount of copper slip or the like?

Well done.

The one comment I would make about re-assembly, is that you must make sure that the mating surfaces at the ends of the tube stack are spotlessly clean, and make sure that the o rings are perfectly sealed. ANY seepage of raw water past the seals allows salt water in contact with the aluminium, which will result in more corrosion. You must only have coolant in contact with the aluminium castings.

 

[rogerthebodger]

Well done.
ANY seepage of raw water past the seals allows salt water in contact with the aluminium, which will result in more corrosion. You must only have coolant in contact with the aluminium castings.

That's what caused the corrosion of my heat exchanger and I had the sealing services built up by welding. I then files /sanded it back to as near the correct profile s possible.

Refitting with a new o ring using silicone grease to ensure proper sealing. I also pressured the final assembly to ensure not further leakage.

Also use an inhibitor in the freshwater side to prevent further corrosion.

 

[MagicalArmchair]

Pretty much all VP engines suffer from this problem. It's what usually kills most of them.

There are many terrifying stories floating around the internet, and photos of heat exchangers of VP engines in varying states of decay. It's seeing those that made me take a long hard look at that bit of the engine before deciding to bite the bullet and start taking it apart. I've contacted VP directly for comment.

inhibitor

What is an inhibitor? How does it work? Noted re the silicone grease, @garymalmgren could I use silicone grease on the green paper gaskets also as that is non conductive?

@Rogershaw once all refitted, how did you pressurise the final assembly? Did you test both the raw and fresh water sides?

Thanks again for all your help.

 

[rogerthebodger]

There are many terrifying stories floating around the internet, and photos of heat exchangers of VP engines in varying states of decay. It's seeing those that made me take a long hard look at that bit of the engine before deciding to bite the bullet and start taking it apart. I've contacted VP directly for comment.



What is an inhibitor? How does it work? Noted re the silicone grease, @garymalmgren could I use silicone grease on the green paper gaskets also as that is non conductive?

@Rogershaw once all refitted, how did you pressurise the final assembly? Did you test both the raw and fresh water sides?

Thanks again for all your help.

Inhibitor I use instead of antifreeze as we dont get temperature low enough you may use an antifreeze for aluminium engines

Radiator Corrosion Inhibitor is a green coloured, hybrid-organic, Type "B", corrosion inhibitor concentrate that protects against cavitation, scaling and oxidisation in vehicles that do not require an Anti-Freeze Anti-Boil cooLant.



Once the sea water stack is fitted and sealed and tightened pressure test the freshwater side to ensure no leaks either out of the stack joint or the stack itself

This can be done by blocking the seawater inlet tipping the heat exchanger up until the outlet is uppermost and fill it with water if there is a leak in the stack you will see bubbles coming out of the stack outlet.

You can also fill the fresh water side with water and pressurize the seawater inlet or outlet in the same was as above and see if any bubbles come out of the fresh water section.

 

[PaulRainbow]

There are many terrifying stories floating around the internet, and photos of heat exchangers of VP engines in varying states of decay. It's seeing those that made me take a long hard look at that bit of the engine before deciding to bite the bullet and start taking it apart. I've contacted VP directly for comment.



What is an inhibitor? How does it work? Noted re the silicone grease, @garymalmgren could I use silicone grease on the green paper gaskets also as that is non conductive?

@Rogershaw once all refitted, how did you pressurise the final assembly? Did you test both the raw and fresh water sides?

Thanks again for all your help.

Just use 50/50 antifreeze.

Grease for gasket, any plain grease will be fine.

 

[jwfrary]

Paper gaskets grease

CAF gaskets (usually green sometimes orange) nothing just clean surfaces

Graphite gaskets clean surfaces.

O rings a bit of whatever they are holding back! Unless It’s water in which case it’s good marine grease.

 

[Beneteau381]

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?

Ive seen pics of people cleaning back to good metal and building up with weld. It takes quite a bit of courage but it is do able. Plastic metal is for a get you home or sell it quick job.

 

[Beneteau381]

And what cools the exhaust gasses in the manifold fresh water or raw water

Fresh

 

[Beneteau381]

Fresh

PS I thought you knew everything! ?

 

[rogerthebodger]

PS I thought you knew everything! ?

The more you know, the more you know how much you don't know.

 

[RichardS]

PS I thought you knew everything! ?

You?

Richard

 

[rogerthebodger]

You?

Richard

Merry Christmas Richard.

I thought Beneteau381 was referring to me but I could be wrong.

 

[Beneteau381]

Merry Christmas Richard.

I thought Beneteau381 was referring to me but I could be wrong.

Nail on head, you!

 

[rogerthebodger]

Nail on head, you!

That's rather insulting as I don't know anything about brain surgery and little about chemistry but having spent over 50 years doing all kinds of engineering design and manufacture including professional engineering training and qualifications. This also included electrical and electronic control systems.

I don't comment on things I don't know about or that someone else as commented on so I have nothing to add.

The point is I know what I do know but also know what I don't know.

If you think differently well that your problem not mine.