I had some expensive work done on my 79 Bobcat with 2.3 lately only to find out that the block has a hairline crack in it. I took it to my mechanic to fix a small water leak . He said it was the head gasket. So off came the head and it was sent to a shop to get redone. He installed it back on wit a new gasket and bolts and it was still leaking. Here there is a fine crack just above the oil filter. I then tried to use J B Weld over the crack to seal it. That didn't work, it just sagged and bubbled and is still leaking. Can I clean it all off and get it welded? Any suggestions?
Tom D.
My uncle did it to his Bobcat about 10 years ago. He is a retired old school military mechanic. He used pieces of steel and welded over the crack. I am not sure what type of welder he used but it held and did not leak. He got probably another 60K out of the thing before he sold it. Then the new owner blew the motor a few days later.
I'm not a master welder or metallurgist (you can only expect so much from a college girl driving a pinto!) The block is an alloy of iron, nickel, and some other stuff I can't remember right now. If you weld it back together, I think you have to use a torch or something to keep the temp up. If it cools off to fast, it will crack either down the middle of the weld or on the edge. Also I don't know what kind of filler metal you would use. Welding it up with steel hard wire (i.e. a mig welder) would result in a poor fix. I don't think I would even try it with flux core (may as well get out the 6011). The block will unalloy where it meets and fuses with the steel making it even more prone to cracking. The different metals will also heat and expand differently. If you tig weld it, you will be able to control the heat a whole lot better and will probably get a better weld from that, plus you may not need any filler rod if it's just a hairline crack. The thing again though is whenever you heat up an alloy you unalloy it to a certain extent because all of the different components of the alloy melt at different temperatures so they separate. JB weld will probably be long gone before the thermostat even opens. I'm not the expert on this; we always threw out or sold cracked blocks. Maybe someone else has successfully welded a block?
Bricker is right.... You CAN weld a cast Iron block, but if you're not a professional welder I don't reccommend doing it yourself. TIG welding is the way to go, but you need to preheat the metal, then keep it hot after, letting it cool slowly.
Sounds to me like you didn't let the JB Weld set properly, or possibly didn't get it mixed right. (I'm not doubting you know how to use JB Weld, but I've done these things myself LOL) Get a side grinder, and grind out ALL the old Epoxy, then clean it down till the metal is shiney (shiney=good) if there's ANY grease or antifreeze on the repair it'll do the same thing again.
Best Of Luck,
Paul
Yes shiney is good. You might want to put a small "V "notch in the crack to help the JB weld to adhere to more surface area.
me and my friend's JB welded a crack in my dad's van block 1 time we had to "V" notch it to get it to hold good. it worked we still have to vn and the JB's holdin good
Cast Iron can be welded by an experienced welder. The TIG processcan be used, and you would be using NICKEL filler rod, and making short beads, stopping to PEEN them (A LOT). This is done to streess relieve the weld bead while it cools. First, grind a groove along the crack, directly on/in it. Then drill a hole at each end to stop the crack. This will keep it from continuing to propagate (travel). Then carefully weld it up, stopping often to peen the weld bead. I have done this before, a LONG time ago. I don't remember preheating or post heating the blocks I welded using this process. It was too long ago, but I don't think I did. Practice on a junk block (Chevy) first, until you get good, then get after it!