Broken Camshaft - Head Gasket Replacement

[bearded_bloke]

Hi all,

I've been having fun with my local garage recently. The head gasket was going on my Ford Focus 2.0l TDI (07 plate) and i didn't have time to replace it myself so sent it in to a local garage to replace.

In doing the head gasket replacement they somehow have sheared my camshaft in two, a straight shear through the shaft where it joins one of the cams (I know its milled down but this is easiest way of describing it!).

I'm struggling to understand what they did to generate the kind of force needed to shear a 1" steel shaft, this happened while they had the cylinder head off and obviously the engine wasn't running but my feeling was i couldn't break it if i tried!.

Their explanation is it happened wile they were torquing down the camshaft as part of standard and correct procedure. Also that camsafts can be brittle and that they can shear during reassembly.

This is something i'm struggling to get my head around, my feel is more happened then they are letting on. Can anyone advise if this failure mode of a camshaft can be expected or if not any ideas what they could have done to cause the shaft to shear?

Many thanks,

Paul

[iantt]

Dropped it on floor! Sounds more like it.

[troy45]

Whole idea of the tightening sequence and torques is to prevent things like that happening

Was the cam snapped while the head was actually off the engine or while they were reassembling it all after the head gasket change?

Pretty certain if the crank and camshaft aren't phased properly when you bolt the camshaft down you can jam valves against pistons which then stops the cam sitting down fully in the cylinder head and possibly snapping it or bending some valves.

[AdeMk1]

I agree with Troy, I'll bet anything they did it while torquing the head down to the block while a piston was at the top of a bore, possibly with a timing lock on the flywheel so the pistons cant move, and the camshaft was holding a valve open on the same cylinder - neither of which will want to move, so the resulting force has to go somewhere until the weakest link breaks - your camshaft.

Exactly the reason i always set the pistons to the centre of the bores before i torque a head down.

Hope they're paying for the new cam/valves and not you.