So I did something silly. New timing belt installed by local mechanic a month ago on our Ralliart. Took timing cover off to see how much slack was in it as I was getting some noice on startup. Tried turning the rear cam sprocket manually and OUCH belt jumps 2-3 teeth (well sprocket more correctly turned 2-3 teeth until belt was able to re-engage).

I have sensibly decided to leave it where it is and will not try and start it under any circumstances. Do you think this is likely to have caused any damage given it has not been started nor turned by hand after the event? I guess there is a possibility that a valve has contacted a piston but I would have thought this would not be enough to cause any damage (ie bent valves)?

Any help would be appreciated.

Steve

As long as you don't wind the engine over until you reset the belt to the correct timing marks you will be fine.You wont have bent the valves jumping the belt by hand.

Yep, should be sweet if you don't crank it over. I've changed a third gen cam belt, had the rear cam slip under valve spring tension, and heard the metallic "clink" noise of a valve touching a piston, but no harm done.

Just a time consuming job setting it all right again though, but at least you get the chance to check everything over and set the tension up correctly and get rid of that startup noise.

Thanks for the reassurance! I was hoping the valves wouldn't be that weak. It is certainly a long way from the scenario where the belt breaks at 4000rpm and causes valves to hit pistons 60 times a second!

There was a lot of slack in the belt so I am sure the tensioner wasn't set up right. The mechanic who did it is normally is excellent but someone else works for him and they are definately not Magna experts.

I remember the sound of the sprocket slipping (wasn't sure it it had at first) and then gingerly counting teeth to the timing marks. 20 on the front, 22 on the rear - bugger.

We live and learn........

when the engine stops it is common for slack to build up between the cams, the tensioner takes it up again when the car starts, although noise can indicate incorrect tension