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Broken engine mount thread bore
by
Turftech
on 12 Aug, 2010 07:48
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I had the rear engine side mount break two days ago. It was the aluminum arm that bolts onto the block that fractured at the bottom where it bolts to the block. One of the upper bolts also snapped, causing damage to the raised threaded "boss" on the block the other upper bolt goes into. Basically broke off a quarter inch of threaded "hole". I have enough of the material that broke off to JB weld it back on, and also enough threaded hole to install a slightly longer bolt to make it work (I hope) But the other raised boss has what is left of the broken stud in it, and it isn't budging with a punch as it is recessed in there a bit, and I don't want to damage that boss as well. I won't be able to get a drill in there to use an extractor, and short of dropping the engine, I can't think of anything else to do other than inventing a "right-angle" drill chuck. lol
Any ideas? It's a '90 Jetta TD. MF engine.
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#1
by
Patrick
on 12 Aug, 2010 08:30
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You don't need to invent the right angle drill, they're around. Not sure you have enough room though. Worth checking into.
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#2
by
Turftech
on 12 Aug, 2010 10:00
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You don't need to invent the right angle drill, they're around. Not sure you have enough room though. Worth checking into.
It's weird that I have never, in 30 years of pulling wrenches and drilling out broken, rusted studs, never seen an angle drill! I just found one at a local tool outfit. Darn! I coulda been rich! As for room, I pulled the right side axle, and moved the oil drain line from the turbo away and have a
little more area to work with. I should be able to deal with it with an angle drill. I have left hand drill bits, and it will probably come out while drilling. Usually does anyway.
The main thing is; is it safe to go with only three bolts holding that mount to the engine? Like I said, I have a chunk of the raised bore that broke off to kind of act like a spacer, but there won't be much more than 1/4 inch of meat at the very bottom of the remaining threaded hole. With the JB weld it wont be very strong at all. It will pretty much be three bolts only that will be handling most of the load. Two at the bottom, and one up top. There are some other threaded holes around there, and I
could try and make a plate with a nut welded to the back of it in that area...? Thats getting pretty intricate though, and would still require me dropping the engine out to do it right. Might as well weld on and tap a new raised bore if I'm going that far. Man, what a pain in the arse!
I'm open to any ideas.
Cheers!
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#3
by
Turftech
on 12 Aug, 2010 11:45
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I've been laying under the car, eyeballing it for a bit. The engine tends to push against that mount arm "mount" under forward load, with the bulk of the force on the lower bolts and the rubber damper attached to the sub-frame. The only time there are any appreciable shear loads on the upper bolts is when down-shifting or reversing. (Or pounding down dirt roads, like what caused this problem to begin with) If a guy was to be real careful, and not try and power up any hills in reverse, or down-shift F1 style, it just might hold up, say, until the planned engine overhaul which could be moved up to this winter? I guess it makes sense to check the other mounts too? which leads to another question; just how much movement is acceptable in these engine mounts? The front one can be pried up a fair bit with a bar (an inch give or take) and the transaxle mount is also easily flexed around a little less.
Cheers again, and thanks for any input.
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#4
by
84tdrabbit
on 12 Aug, 2010 13:26
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as long as there are 2 bolts holding 100% on the bottom, i would think you should be fine. the 2 bottom bolts take the most load. the 2 top ones are there to keep things from moving around too much. if it were a bottom bolt hole, i would say fix it right, but being a top hole, its not nearly so important IMHO. as long as you have one still holding the top tight..
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#5
by
theman53
on 12 Aug, 2010 14:50
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Here is what I would try. Take a fully threaded bolt and cut the head off of it. Make it into a stud and thread that into the broken mess with a little medium thread locker. Hopefully then it won't be moving in the block. The nut on the other side will just be pulling a little from the threads and shouldn't hurt your JB weld as bad as twisting force if it were a bolt. Other than heating the cast and actually welding it back on I think the stud would be the best chance of success.
I am sure the bolt should hold for a while, but unless all is welded and fixed 100% it is all a gamble
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#6
by
Turftech
on 12 Aug, 2010 15:42
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Here is what I would try. Take a fully threaded bolt and cut the head off of it. Make it into a stud and thread that into the broken mess with a little medium thread locker. Hopefully then it won't be moving in the block. The nut on the other side will just be pulling a little from the threads and shouldn't hurt your JB weld as bad as twisting force if it were a bolt. Other than heating the cast and actually welding it back on I think the stud would be the best chance of success.
I am sure the bolt should hold for a while, but unless all is welded and fixed 100% it is all a gamble
Great idea! Like you say, that'll do it as good as it can be without heat and nyrod! There is a quarter inch or so of good threads, along with a nut that I have ground down to match the angle of the broken end. The stud, JB and some loctite should work pretty good! Sometimes you can't see the forest for the trees!
Thanks for that buddy!
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#7
by
Turftech
on 16 Aug, 2010 06:01
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Just an update
The stud solution worked great. Ended up using a 5/16 stud as metric NA here. Used it like a tap so it holds very well. The broken bolt came out just by using a left handed drill bit in my new right angle drill from Canadian Tire. ($70) Found a whole host of other issues. The alternator/AC bracket bolt on the bottom was missing and the water pump had come loose and was leaking where it attaches to the block.
Amazing how much smoother it is with the new mounts. I'll post a few pics when I'm done.
Thanks again!
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#8
by
theman53
on 16 Aug, 2010 06:28
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sweet!
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#9
by
ORCoaster
on 16 Aug, 2010 21:41
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Turftech, I agree with the one problem seems to lead to another with these cars. I recently purchased an 81 Rabbit and in my checking of stuff that needs tuning I am finding all kinds of weird stuff. Like the drivers window yesterday. Thought I could pull the lever and spring crank out to lube it up as the window comes down smoothly but then was hard to crank back up. What do I find? The lift on the bottom of the window glass is nearly in two pieces. Two more ups and downs and I bet it would have come apart on me. Need to tack it back with the welder.
The PO just put in a new radiator in this beast/ bunny before I bought it. His uncle warned him of overheating the diesel. In my digging around for the horn relay I find the 30 amp fuse in the top corner where it is just a pain to see and it is burned out. I wondered if the whole radiator fix was due to him not being able to see the fuse.
Other things are happening too but your comment struck a chord with me. My son tells me I need to adopt his don't look don't fix policy. I wondered about his car all the time. How could it keep going with all that was visibly wrong.