gti00eater

a fella i know who is a mechanic says if the timeing belt snaps on a impreza it doesnt cause any damage is this true? cheers

collierm

You sure he's a mechanic and not a comedian??

speye91

scoobyboy

turbos it will but early n/a it won't

RB5_245

On a turbo it will do damage.

scoobboy

iTrader: (3)

He is correct, in fact cut the timing belt and start the engine and take her for a long drive

Turbotits

iTrader: (2)

They do indeed cause damage. Although if you read an autodata timing belt book which is considered to be one of the best all round timing belt guide books and most garages have one, it does indeed say the turbo is a 'non interference engine'

If this chap has read it in the book then he can only go by what it says.

rks275

it depends ive know people had cambelts snap another one fitted and the car has been fine. it depends on whether or not any valves are open at the time of it snapping and how far open they are.

you could get lucky you could not!

ive also know 3 week old belts snap before also

Shark Man

Things is, I have found Autodata books to be full of errors on a number of occasions with the various cars I've used it for. It cannot be completely trusted (read their disclaimers ).

The Impreza Turbo engine does suffer from both valve to valve contact (one have can touch and bend the opposing valve (refer to hemispherical/pent roof combustion chamber and valve angles). Which is why the Impreza workshop manual makes important note of turning each cam pulley in the a particular direction when replacing a cambelt. They also suffer piston to valve contact.

The problem is when a valve does bend, most of it is elastic deformation (i.e it returns to its normal state), but there is also a small amount of plastic deformation (permanent) which is barely a millimeter. The result is when the valves are inpected whilst still it in the cylinder head, they look fine, the belt is replaced and engine ran, it will appear to run fine. It may have a tappy top end - which often gets pointed at tappets etc but infact is the valve hitting the valve seat incorrectly as it doesn't align. This forces the valve to bend and unbend as it open and closes, the long term result will eventually end up with damaged valve seats and guides, plus the worst case a valve snapping off and mulching up the entire cylinder - more or less wrecking the engine completely.

This is what happens when a valve drops or breaks off:

https://www.scoobynet.com/drivetrain...=1#post6968749

(credit to simbo)