I removed my sump last week to take the bits of dipstick guide out of it that I had dropped down there when I broke it, and also to give it a bit of clean after 10 years of use. Putting it back on I applied the sealant and then only lightly bolted it in due rain starting to fall (I'm doing it on the drive)
I went back today to torque it to the correct settings with a new torque wrench and following the advice of the Haynes manual tighten the bolts going into the block and the gearbox until they were firm-ish. I then torqued the gearbox bolts to 40NM before starting on those going into the block in a diagonal pattern with the wrench set 15NM.
The wrench seemed to behave a bit funny at this lower setting, jumping rather than smoothly switching to a 'spin' type mode as it had done at 40NM - (It also felt like it was taking more than 15NM, but that could easily just be me not knowing what 15NM feels like) Anyway on about the 8th bolt it jumped again as it hit the torque setting and sheared the bolt off, not good but it was about the most accessible bolt so I figured that whilst I wasn't going to look forward to trying to get it out it wouldn't make any difference that the sump was attached and therefore carried on.
Two bolts later and the same happened again and I now started to question the wrench so tried it on some bolts that I had used it on to get the correct torque. In some instances it clearly wanted to apply more torque without stopping, although not on the 40NM bolts, only the 15NM ones. I then decided that shearing further bolts on the sump would probably not be a good idea and instead used it on one of the a nuts that hold the charge pipe on and this time the jump caused the nut to cross thread so that it now just spins on the bolt (not the best result either as the charge pipe is currently not attached).
Sorry for the long story, buy my questions are -
Is this the product of using a rubbish torque wrench (it is a £45ish draper one) or have I done something wrong?
Any pointers on removing sheared bolts?
Is it safe to tap a large hole in the block if I need to drill the ends out?