If you have a timing belt change due on a 20vT you must read this...

[TheCrispyNoodle]

2 weeks ago I suffered a 'catastrophic' engine failure on an AAN. The timing belt which according to the cars previous service history was changed 15k/2 years ok was first believed to have slipped causing the usual valve damage etc. Yesterday I discovered the root cause was a sheared key on the lower crank timing pulley that mates with the crank pulley bolt. This has disintegrated causing the timing pulley to spin on the crankshaft. Ouch.

Some of the various guides to doing a 20vT timing belt change do refer to inspecting this pulley/key for wear and replacing if necessary. I cannot stress how important this would appear to be, the lower timing pulley is still a readily available part and well worth the effort of changing it given the risk and cost of correcting its failure.

The previous timing belt change was performed by 'joes garage', and it seems that changing the water pump, tensioner and temperature sensor were also considered too much effort. The crank pulley bolt was insufficiently torqued/loctited and this seems to have eventually worked lose causing the increased stress on the pulley key. Grim.

Lessons learned.

1. Don't let anyone near these engines who doesn't know what they are doing.
2. Assume this part is a must when doing a timing belt change and at the very least inspect it if not spend the extra £50 on the part and change it regardless. EFI and 034 motorsport do hardened versions if you are really paranoid, for obviously more than £50.

The only thing I can be grateful for is it not happening until the day after I returned from a family holiday covering 950 miles to, around and back from Devon.

I've now seen my engine disassembled into more pieces than I ever want to again....