Sunday, 10 August 2014

E60: Snapped Head-Bolts! No progress.

Well this has been the most fruitless weekend to date. First I discover the simple sump cannot be removed without lifting the engine and lowering the subframe. I am now the owner of a Clarke engine-crane, not cheap at £179.99, but it moved the job along. Next I find that to lower the subframe, almost everything must be unbolted from it - anti-roll bar, steering-rack etc. - and, once the mounts are unbolted, there is nothing stopping the engine from dropping straight onto you if something fails. I figured if I'm having the engine suspended freely above me while I work then it's best to get as much weight off it as possible, so began removing the head. The camshafts etc. came out in record time, but when I got to the head-bolts at about 12.30pm, the whole weekend's work ground to a halt.

Magnet to catch metal swarf from the drill.
Ok, it happens to us all from time to time, but I didn't expect snapped head-bolts as an added problem with the 530d rebuild. First my E14 torx-socket burst open, causing a trip to Halfords for two new ones, then 4 of the bolts snapped. Four! What a pointless setback. I did the correct removal sequence, so I must have over-tightened the head or they're just not ready to come back out after only 2 weeks, but as I got down to the last two head-bolts one of them snapped in the most awkward way imaginable - just the top of the head, leaving the giant collar and washer still incredibly tight against the head. All the other bolts did crack off slightly, the almighty creaking sound, but after that a further 3 of them stuck solid and the heads duly snapped off one by one, despite re-tightening the surrounding bolts. This hasn't half messed up the un-tightening sequence and has put the rebuild completely on hold.

Determined not to be drilled off, the head was finally
cracked off with a chisel and screwed out by hand.
I battled away until 3pm with the drill-bits I had available to me, before caving in and rushing to B&Q to buy a new 8 and 10mm titanium, again not cheap at nearly £17! I placed a large block-magnet in the head next to where I was drilling and held a smaller one to the other side in order to catch as much swarf as possible, but I will still have to give the cyl.-head and rockers a good blast in the parts-cleaner at work. The plan was to drill down the centre of the bolt head, boring it out gradually wider until the head broke away from the washer. Life is never so simple. The hole was slightly off-centre, so part of the shank was still attached even though I'd drilled well down it, so I began reaming the hole around the bolt head as much as possible. It was still stuck solid, so as a final shot in the dark I drilled a smaller hole in the rim of the bolt head and hit it with a chisel. To my amazement it cracked off and I was able to drift it round enough to become loose. I tried repeating the chisel process off the bat with the other 3 bolts, but they're having none of it, so I will have to bear out the drilling and reaming again. This is not going to be a quick thing, let alone getting that subframe down. Ah well, another week passes.

Problems to overcome:

  • Drilling out stuck head-bolts.
  • Getting the subframe down.
  • Identifying the correct piston type.
  • Clearing the head of any drilling debris.
  • Identifying main source of oil leak.


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