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just curious?

Usually a thrown connecting rod. Now what causes that can be any of a number of things. Hydrolocked? Bad maintenance? Over-revving? Busted valve? You'd really have to look inside to see if there's enough evidence to trace it, but the best bet is that you'll find that one or more rods are not all there any more.

Those of us who have owned old air-cooled VW's at some time are quite familiar with this phenomenon. It's really quite amazing how big the hole can be when a rod decides it's time to part ways with the rest of the engine. VW's usually sucked a valve. Most often, exhaust #3 would burn out, break off, and jam the piston. Blam. End of engine. I still have in my shop a piston from my 71 bus that has the valve head embedded in it upside down. I never found all of the rod.
 
i think it may have been hydrolocked. but he changed the oil right after taking the sparkplugs out and getting all the water out. but was this damage from the fact of hydrolock?
 
Yes - water doesn't compress, so something else has to give.

I've also had it happen (in my 1987XJ 4.0) due to an oil pump failure - there was significant heat damage to the big end of the #6 rod (the one that let go,) and a hole about big enough to put my fist thru resulted from the "explosion."

A new #6 rod, new crank and bearings, and new lifters (the pushrods were all still straight, and the rockers weren't cracked. I also dye-checked the other five rods...) and I put another 50K on that engine, before it wasn't sucking enough air to start anymore. I knew I should have done a re-ring while I was about it...

5-90
 
5-90 said:
Yes - water doesn't compress, so something else has to give.

I've also had it happen (in my 1987XJ 4.0) due to an oil pump failure - there was significant heat damage to the big end of the #6 rod (the one that let go,) and a hole about big enough to put my fist thru resulted from the "explosion."

A new #6 rod, new crank and bearings, and new lifters (the pushrods were all still straight, and the rockers weren't cracked. I also dye-checked the other five rods...) and I put another 50K on that engine, before it wasn't sucking enough air to start anymore. I knew I should have done a re-ring while I was about it...

5-90
Click to expand...

Ok, I'll bite: what did you do about the hole?
 
Matthew Currie said:
Ok, I'll bite: what did you do about the hole?
Click to expand...

The piece was loose, not missing. I was able to remove it and apply a little VersaChem metal-bearing epoxy/cold weld compound.

I also dropped the pan and "welded" it from the inside as well - so the edge was sealed, the inside was sealed, and the outside was sealed. Since the hole was in the skirt about two inches above the oil sump rail, it worked neatly (and didn't leak!)

I probably won't use that block for anything I've got in mind, but the rest of it is still in good shape...

5-90
 
5-90 said:
The piece was loose, not missing. I was able to remove it and apply a little VersaChem metal-bearing epoxy/cold weld compound.

I also dropped the pan and "welded" it from the inside as well - so the edge was sealed, the inside was sealed, and the outside was sealed. Since the hole was in the skirt about two inches above the oil sump rail, it worked neatly (and didn't leak!)

I probably won't use that block for anything I've got in mind, but the rest of it is still in good shape...

5-90
Click to expand...

I guess that's the diff between an Jeep and a VW, eh? That old magnesium-aluminum alloy was a little brittle. Past 40K miles on an "upright-fan" bus, you'd do well to carry a broom.
 
Matthew Currie said:
I guess that's the diff between an Jeep and a VW, eh? That old magnesium-aluminum alloy was a little brittle. Past 40K miles on an "upright-fan" bus, you'd do well to carry a broom.
Click to expand...

Oh, yeah. Those engines were light, but Gawd forbid you'd break the 'case somehow...

I do like the high-nickel iron alloy that AMC used... If I'd had time and taken the block out, I could have just had the thing welded (I know a couple guys who can weld cast iron reliably...)

5-90
 
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