A A A A Author Topic: Weird Sheared Bolt on Water Inlet  (Read 43 times)


Weird Sheared Bolt on Water Inlet
« Started on: 26-Mar-20, 16:04 »
I'm curious how this happened and how to effect a repair.  The photo shows the LHS water access flange on top of the cylinder block.
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This is the sequence of events:
Stripping engine for Triple BP;
Son sheared off one of the bolts that secured the connection flange;
Tried Inox soaking, failed to move it with vice-grips;
Tried Inox soaking, mechanical shock, failed to move it;
Tried Inox soaking with plasticine dam around the broken bolt and topping up with Inox twice a day for a week, failed to move it;
Used electric heat gun etc, failed to move it;
Used MAPP gas torch at a distance to heat the inside of the flange where red arrow is pointing, failed to move it;
Decided to drill and attempt to use easy-out, or to drill oversize and helicoil.  Hacksawing broken bolt close to the cylinder block was hard work, bolt didn't appear to be normal material;
Tried to centre-punch the bolt preparatory to drilling and blunted my centre-punch;
Brand new drill bit failed to make any mark on the bolt;
I subsequently noticed that near the point of the red arrow there was some deep erosion/ corrosion of the alloy casting (just visible, or maybe only just imaginable, in the pic).

Has someone done a previous repair using a very hard bolt (or stud, I don't know which as my Son threw away the sheared off part)? 
Given where I'm at, what's the best way forward?  I'm thinking about buying a special drill bit and trying the easy-out and/or helicoil route.  Perhaps with some JB Weld to fill in any eroded/corroded areas in the flange (after wire brushing with the Dremel)?


Re: Weird Sheared Bolt on Water Inlet
« Reply #1 on: 26-Mar-20, 17:29 »
Try a cobalt drill, they are made for hardened material and may be just what you need.

Maybe the bolt is stainless steel which is hard compared to mild steel. You will probably not budge it with an ezyout so I would consider drilling a 2 or 3mm hole through the centre of the bolt followed by a 5mm hole. You should then be able to use a 6mm tap to create a new thread. Typically this results in the original bolt finally “letting go”.

If the drilled hole ends up off centre you should be able to use a helicoil kit to repair the thread once you get the old bolt out.



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