snapped timing belt

Joined: 14 Nov 2008 Location: adelaide

hi everybody

i am looking for some help as the title suggests

on the weekend i changed my timing belt broke the coolant air bleed today after finding time to get one and started it

thats when it all went bad it ran for about 5 mins then it stalled and now it wont start

does anybody have any ideas what has gone wrong

please and thanks for your help

i have changed the subject after investigating furter and finding the problem

any ideas on what i should do now

ie mechanic or get into it myself and how much damage can a snapped belt do at idle revs

Joined: 11 Jun 2005 Location: nsw maitland

more info?
What engine ?
what year?
what vehicle?
etc

Joined: 14 Nov 2008 Location: adelaide

ahh yes lol left that out
its a 1994 300TDi disco

Joined: 11 Jun 2005 Location: nsw maitland

do you know why it snapped?

possibility of bent valves
it might be worth while removing head and checking valve condition

Joined: 14 Nov 2008 Location: adelaide

no idea havent even pulled it out yet i opened it up and its all in behind the pulleys so going to tackle that tomorrow
it could only be a bad belt or over tensioning as far as i can imagine will i need to compression test the motor first or is it best just to pull the head and replace all the valves

Joined: 03 Mar 2003 Location: St Helena, Melbourne.

jussy wrote:

no idea havent even pulled it out yet i opened it up and its all in behind the pulleys so going to tackle that tomorrow
it could only be a bad belt or over tensioning as far as i can imagine will i need to compression test the motor first or is it best just to pull the head and replace all the valves

You will only bend the pushrods and maybe damage a rocker, just lift the rocker cover off and check the pushrods before touching the head.

Joined: 03 Nov 2002 Location: Lake Macquarie NSW

Sounds to me like either the timing belt has jumped some teeth and valves collided with a piston, or the belt has tracked of a pulley.

When a belt has been changed on these engines, before the front cover is re-fitted, the motor should be rotated through a couple of cycles and the timing re-checked.

When replacing the timing belt, it is false economy to not fit a kit that includes a new tensioner and a new pulley that fits on the crank. Also ensure the pulley on the crank has flanges on both sides (early pulleys had no flanges and the flanges wear away on used pulleys).

The belt should be tensioned in accordance with the latest service instruction, which includes a revised torque of 11 Nm, not 14 Nm as stated in the workshop manual. If you don't fully understand how to achieve this tension then ask - it is not a torque on the mounting bolt.

The timing belt tension was reduced because it pulls the pulls the pulleys out of alignment and makes the belt track of. Usually wears the edge of the belt away until it fails, and/or wears the flange on the pulley away allowing the belt to track off further.

Edit: because of vibrations, screw threads should be loctited. And make sure the nut for the harmonic balancer is tightened correctly (difficult).

Because the valves are perpendicular to the piston crown, it is most unusual to bend valves when they hit the piston. Usually only bend push rods and sometimes rocker arms fail.