Leaking Overflow Tank

[Theorangetiger]

I'm finishing a MKII restoration for a friend of a friend of a friend and have discovered a leak in the header tank, which had been chrome plated. It's a very slow leak but water was showing up on the frame rail below the tank. It's so slow that I couldn't locate the exact spot of the leak on the tank with it in place. My best guess was the joint between the two halves of the tank which I had dealt with on my own car many years ago.
I removed the tank and a pressure test at a radiator shop revealed a very straight crack running about 2" long ways along one half of the tank on the bottom side. Fortunately, it's in a spot that won't show when installed. The seal between the two halves of the tank is in great shape. The radiator guy was willing to grind the chrome away just enough and try to braze it up but did not have good luck with that. There is now a crack/leak on the other side of the tank directly in line with the old one. It seems that this will be an ongoing process, seal one and create another etc. I'm thinking this is not likely corrosion because of how straight the lines are.

Has anyone experienced anything similar?

I'm open to suggestions but because it is useless as is, one possibility would be splitting the two halves, seeing inside and hopefully being able to repair from the inside. The fact that it's been chrome plated only complicates things but I'll just have to deal with that.

Thoughts, suggestions?

TIA

 

[Austin Healer]

I'm finishing a MKII restoration for a friend of a friend of a friend and have discovered a leak in the header tank, which had been chrome plated. It's a very slow leak but water was showing up on the frame rail below the tank. It's so slow that I couldn't locate the exact spot of the leak on the tank with it in place. My best guess was the joint between the two halves of the tank which I had dealt with on my own car many years ago.
I removed the tank and a pressure test at a radiator shop revealed a very straight crack running about 2" long ways along one half of the tank on the bottom side. Fortunately, it's in a spot that won't show when installed. The seal between the two halves of the tank is in great shape. The radiator guy was willing to grind the chrome away just enough and try to braze it up but did not have good luck with that. There is now a crack/leak on the other side of the tank directly in line with the old one. It seems that this will be an ongoing process, seal one and create another etc. I'm thinking this is not likely corrosion because of how straight the lines are.

Has anyone experienced anything similar?

I'm open to suggestions but because it is useless as is, one possibility would be splitting the two halves, seeing inside and hopefully being able to repair from the inside. The fact that it's been chrome plated only complicates things but I'll just have to deal with that.

Thoughts, suggestions?

TIA

probably the best option would be to have a chrome shop strip it. then it'll all be bare brass. he should have just soldered it instead of brazing. less heat that way

 

[Theorangetiger]

Probably a good idea, thanks. I was trying to preserve the fresh chrome but that seems to appear impossible now.

Thinking about it some more, the actual holes in the brass could be caused by corrosion and be more organically shaped but the chrome splits in a straight line.

 

[Austin Healer]

Probably a good idea, thanks. I was trying to preserve the fresh chrome but that seems to appear impossible now.

Thinking about it some more, the actual holes in the brass could be caused by corrosion and be more organically shaped but the chrome splits in a straight line.

MK2 overflow tanks are really hard to find. They differ from the Mk1 and Mk1a in that there is a fill to level strap of brass under the cap... makes it worth repairing!

 

[HolyCat]

MK2 overflow tanks are really hard to find. They differ from the Mk1 and Mk1a in that there is a fill to level strap of brass under the cap... makes it worth repairing!

If the Mk II overflow tank is completely shot and not much metal to braze, can you remove the overflow level marker and install in a Mk I/IA tank? As already noted, Mk II parts are hard to come by.

 

[Austin Healer]

If the Mk II overflow tank is completely shot and not much metal to braze, can you remove the overflow level marker and install in a Mk I/IA tank? As already noted, Mk II parts are hard to come by.

yes, the entire thing comes apart once you melt out the solder. I split mine so I could knock out the usual dents they all seem to have.

 

[michael-king]

The UK suppliers make a new header tank to MKIA spec iirc.

 

[boss-tiger]

If it is a brass tank I would replace. My thougt is that once you get one stress crack in a brass tank, you probably have two more waiting to happen in the future. With that said, I have seen some repairs last (but not for me). I have assumed that the brass tanks that get the stress cracks where either over tightened in the clamps or maybe frequent engine overheating stretches the brass (yep there are some Tigers out there than can overheat). On filp side there are plenty of cars out there with brass tanks never having a problem. At least it is easy to replace (much better than a bad throw out bearing).

 

[Theorangetiger]

I'm going to undo the seam, split it apart and have a look inside. That should tell a lot and determine the next steps.

 

[Austin Healer]

I'm going to undo the seam, split it apart and have a look inside. That should tell a lot and determine the next steps.

you can always reinforce the cracked areas from inside with narrow strips of brass....

 

[volvoguys]

you can always reinforce the cracked areas from inside with narrow strips of brass....

Would lining the tank be a reasonable option?

 

[0neoffive]

Would lining the tank be a reasonable option?

I've done that. works fer me.

 

[Theorangetiger]

I did get it split apart and there were two sets of cracks in each half. I can't get a decent photo to show them. I'm going to thoroughly clean them up and basically tin over them with solder which should seal any leak.

What material is used to line the tank? I could apply something while it's still split in two but it's unlikely it would stand up to the heat used to solder them back together.

 

[Austin Healer]

I did get it split apart and there were two sets of cracks in each half. I can't get a decent photo to show them. I'm going to thoroughly clean them up and basically tin over them with solder which should seal any leak.

What material is used to line the tank? I could apply something while it's still split in two but it's unlikely it would stand up to the heat used to solder them back together.

you would have to wait to use any kind of sloshing material until the tank was reassembled. But if you tin the cracks over, or solder brass strips over the cracks it shouldn't be necessary.

 

[volvoguys]

Would lining the tank be a reasonable option?

Thank you, Sean.

 

[Theorangetiger]

It's been a few weeks but after a LOT of back and forth, I seem to have managed to repair the tank. After splitting it and making satisfactory solder repairs to the cracks from the inside, I soldered the two halves back together but the increased heat required for this undid the repairs inside. I took it back to the radiator shop and the owner who was very patient with me pressure tested it and it failed, leaking along the cracks again. I decided this would continue if I split it again so I did the tidiest repairs I could on the outside. After two more trips for pressure testing, it finally passed the test. As I said earlier, most cracks were in spots that wouldn't show when installed. There is a small one that can be seen in the photos and a big ugly scar that requires a mirror to see. After all of this, the chrome still shows very nicely.
This required quite a few hours I hadn't figured spending here but I do think my soldering skills have increased a bit. Also, this would have been MUCH easier without the chrome.

I contacted customer service at POR 15 and after explaining the situation they said their fuel tank lining process would work here and hold up to the water and anti-freeze but I don't think it will be necessary now.