Rear piston appears slightly melted. What to do about it?

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M37M35

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Well.... I got the piston and liner out today.....

The good news: I found out where the antifreeze is leaking from.

The bad news: It's coming from a crack in the block behind the liner.

View attachment 664479View attachment 664478

Makes me wonder if the melted piston and cracked block could be related...

So now I have to figure out where to go from here... Thoughts? Ideas?
 

Jbulach

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I quickly skimmed that tread, my recommendation, unless your willing to use heat, pre, during, and post welding, I wouldn't waste your time trying to weld the crack.
I don't know anything about Normacast rods, but have always had great success with plain old nickel 55 electrodes, but NEVER cold.
I also wouldn't recommend using silicone or anything else that may act as an insulator behind a dry liner.
I would call around to a bunch of older engine builders and see if they have any solutions. Maybe a sealer to put on the liner or cut the bottom of it for a o-ring??? I know cracking used to be a common problem with a lot of older engines with dry liners.
 

texas30cal

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If going to repair I would grind out the crack, preheat, and braze it. I've repaired other issues with several blocks and many cast iron machinery parts this way, have always had much better luck with brass than welding. There is even a higher strength brazing rod that's not just regular old yellow brass but can't remember the name.
 

texas30cal

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There you go!! I couldn't remember how it was identified but could always tell by the color as the stuff we had was less yellow and more toward silver in color
 

rustystud

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Having welded up literally tons of cast-iron the only way to get it to hold is using "Ni-Rod" and "TIG" welding. You also must pre-heat it and then "peen" it afterward during the cool-down period. We had a customer at "Kolstrand Marine" (where I worked as a welder) that had cast-iron valves that he was welding for some special project. I spent 6 months straight welding up that junk. The real problem with any "cast" item is the "inclusions" in the material, especially in cast-iron. You would be happily welding along when you suddenly hit an inclusion and the molten metal would burst on you. Just like hitting a steam pocket. There where times I spent over an hour trying to weld a 1 inch long seam because of all the inclusions in it. Now having said all this if this was my block I would toss it out and get a new one. You can "never" trust a weld on cast-iron" . Sure as the sun rises in the east someday the weld will fail and if your far from home too bad for you.
 
Last edited:

teletech

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I used to use Nomacast and similar N-55-N99 rods for welding cast iron, but I switched to an inconel rod from Aircraft Spruce a couple years back and couldn't be more impressed by this stiuff. It's $200/Lb but seems to flow into the casting porosity almost like a braze.
That said, if it were my truck, I'd replace the block. I too would rather braze than weld for a crack like that, less risk of something happening in the heat-affected zone, it seals better, and the brass has a little give. I'd eventually relax with a nice braze, I don't know that I ever would with a weld.
 

orren

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Anybody heard of using puddle welding. An old machinist/chemist friend of mine
used this to weld up cast iron. He used an oxygen/acetylene torch and puddled the
metal all around the crack. Then when finished he immediately placed the piece in a bed of saw
dust so it would cool down slowly for a couple of days. As far as I know the piece
he did for me is still working OK for 20 years.

Sometimes, as in my case, you just can't get a replacement part so you have to
take chances on weird methods.
 

Jbulach

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Yes, you can actually do this with a TIG welder as well.

You would typically want to use a filler metal though, in the case of cast-iron, that would be a nickel alloy. Trying to re-fuse cast without a filler rod typically doesn't work very well (cracking), you want to minimize the melting of your base metal as much as possible.
However, it sounds as if he knew a little bit about the procedures for heating and cooling cast, that's probably why it worked for you.
Although I typically run hotter than he most likely did. I would set sawdust on fire after welding. However sometimes you can only get as much heat in the part as you can get!

If I can fit the part in my rod oven, I typically use that for a real slow to cool down. If that's not practical, I try to blanket the part in layers of fiberglass insulation best I can.
 

Jbulach

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I used to use Nomacast and similar N-55-N99 rods for welding cast iron, but I switched to an inconel rod from Aircraft Spruce a couple years back and couldn't be more impressed by this stiuff. It's $200/Lb but seems to flow into the casting porosity almost like a braze.
That said, if it were my truck, I'd replace the block. I too would rather braze than weld for a crack like that, less risk of something happening in the heat-affected zone, it seals better, and the brass has a little give. I'd eventually relax with a nice braze, I don't know that I ever would with a weld.
I would be willing to bet, partially judging by the price, that all these fancy names, are just brand names of typical nickel alloys or maybe a variation of somewhere between a 55% and 99% nickel? Kind of like vice grips and channel locks...
If you get a nice preheat on your part nickel will flow out very similar to bronze.
I also wouldn't rule out the fact or possibility of brazing the block, especially with the cramped hard to get area that you will be working in. Brazing will also be a lot cleaner and easier to protect the crank and the motor from all the other debris you're going to get working with nickel rods.

I would still talk to some engine shops for advice, or just replace the block before trying to weld that though.
 

Jbulach

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Having welded up literally tons of cast-iron the only way to get it to hold is using "Ni-Rod" and "TIG" welding. You also must pre-heat it and then "pen" it afterward during the cool-down period. We had a customer at "Kolstrand Marine" (where I worked as a welder) that had cast-iron valves that he was welding for some special project. I spent 6 months straight welding up that junk. The real problem with any "cast" item is the "inclusions" in the material, especially in cast-iron. You would be happily welding along when you suddenly hit an inclusion and the molten metal would burst on you. Just like hitting a steam pocket. There where times I spent over an hour trying to weld a 1 inch long seam because of all the inclusions in it. Now having said all this if this was my block I would toss it out and get a new one. You can "never" trust a weld on cast-iron" . Sure as the sun rises in the east someday the weld will fail and if your far from home too bad for you.
If you have an inclusion, you simply stop welding, reheat around the weld area, grind the inclusion out and start again, you don't want to try welding over them.
 
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