I have a 98 A4 quattro 2.8. I did a timing belt change following a DIY and everything went great, marks and cogs all lined up and belt tight, put it back together and ran smoothly. Then I replaced the clutch, its done and worked great, but now all of a sudden I got a rough idling noise sounding like a diesel engine, sounded like the timing belt was rapping against something. I removed the timing belt covers and drive belt and can see that the belt is loose on the top between the upper cams, it touches the water pump pulley, but I can turn the pully by hand, the lower half of the belt is tight. Can you help me find out what happened? It looks to me like the passenger side cam may be one tooth off. Will I need to remove the entire front end again and reinstall the belt. I just want to know if there are any possible short cuts to doing all that work again.

 

Update, i removed everything to get to the belt, cranked the engine by hand and noticed the timing belt idler was not doing its job. I loosened the bolt on it and it popped tension back on the belt and all my timing marks still line up on all three pulleys. So I suppose I over torqued the idler bolt?? Even though the car was running, do you think I caused any damage to the valves or pistons? I want to be double sure before I start it up again.

 

More info, I found that the torgue spec for the timing belt idler pulley bolt was to be 15 ft lbs. I had it way tighter than that. The DIY I was using mentioned nothing about torque specs, beware of DIY's that may lack vital info!! I know have the proper tension on the timing belt again and since the engine was running when I first caught the problem, I am hoping that indicates no valve damage was done.

 

Wow good luck man hope nothing is banged up.

 

I doubt you did damage.. 1/2 - 1 tooth off shouldnt, and yours really wasnt... Good thing you caught it though.

 

Back together, and runs great. Thanks.