Timing belt change - Is this method OK?

[CP951]

Hi,
Please advise. I know the timing is right before swapping the belts. If I can't be bothered cranking the engine to TDC. Is it OK if i just mark the position of the old belt with the cam and crank sprockets, remove the old belt, put the corresponding marks on the new belt and just fit the new belt over where the marks are with the sprockets? I thought this is accurate enough. What do you think?
Thanks

[Fat Audi 80]

I would have thoughtthat would be fine as long as your pulleys don't move in the mean time while the belt is off...

I have never done a cambelt on the I5 engine before though....

[WabTheKing]

worked for me in the past

[CP951]

Thanks very much. I feel much more confident doing it now.

[iain1067]

don't see why not provided nothing moves if it does then you may well be off a tooth or 2, i would still go for the timing marks, the one on the gearbox bell housing maybe hard to see once found i would amrk it with a dot of white paint, previous experience on 10v I5 engines is that the front timing marks on the cam cover aren't all that accurate use the gearbox and camshaft markings, no harm using your own markings as well, belt and braces etc etc


iain

[Corey]

But if you don't tension the belt correctly how will you it hasn't moved a tooth?

Why is it an issue to align the engine, couldn't be simpler. 1 mark the cam sprocket and one on the flywheel (ignore the pathetic mark on the pressed steel lower cover as they are never 100% correct).

For the sake of 2 minutes checking are you willing to risk your engine?

[mcandmar]

If you take the spark plugs out and you can turn the engine over by hand. And i'm not convinced you can tension the belt properly without it being at TDC. Just seems wrong to me...

[Corey]

My next question is if you cannot be bothered to align the engine how are you locking the crank to undo the crank pulley?

You can tension the belt without it aligned but you have absolutely no way of knowing if it is correct.

[Fat Audi 80]

I have never done this so forgive the silly question, but do you not replace the belt on the correct teeth and THEN tension, so the tensioning should not affect the belt to teeth position??

Or have I missed something?

cheers,

Steve.

[Corey]

If you don't have the slack on the correct side when tensioning it moves the timing out slightly.

[4WheelDrifter]

I think there must be something he is not telling us. Otherwise why not use the original timing marks? It doesn't really make sense.

I always turn the engine over by hand after I've completed the job, just to make sure the marks still line up and the tension is still ok.

[prosty]

Why is it so hard setting the car in TDC? Just do it before you remove the cam belt. remove 1 or two plugs and turn it correctly..

[CP951]

Dear all,
Many thanks for your input. I intend to remove the pulley bolt by impact wrench and tighten by torque wrench (thought probably by impact as well), therefore I won't be locking the crank pulley. Even if I do need to lock it up, I'll probably do it by gearbox + handbrake with the car sitting on ground.
I find the original timing marks vague, I am not that convinced by them.
I assumed even if the belt is slack, the cam and crank relationship should remain constant from the "belt" perspective as the number of teeth (on belt) between the two fixed points I made on the cam and crank pulleys should remain the same irrespective of belt tightness.
I also assumed that even if I have moved one or both pulleys in any direction (obviously not like turning them), I could still realign the mark I made on the pulleys with the marks I made on the new belt, hence the cam and crank relationship will remain unchanged. Am I correct?

[mcandmar]

Another thing to note is the crank pully has a small cast metal gear for the cam belt which is prone to failure, and in my opinion removing/torqing the bit nut with an impact gun isnt going to do it any favours.

The proper way to do it is with the audi locking tool so you lock the pully static and torque up the big nut. Locking the crank with the gearbox/brakes isnt that good an idea either to be honest, i think the workshop manual specifically tells you not to do that.

As for the cam/crank relationship staying constant, i would'nt bet on that. If you ever tried to turn a cam shaft over on its own you will find it jumps from position to position because of the force of the cams pushing against the valve springs. Its possible you could stop an engine between these two points, slacken the belt, and the camshaft will jump a few teeth off. Use the TDC marks, just to be sure.

Either way buy a new gear first, if it shears off its locking key your valve gear is going to get it. A few members have BTDT!

And as 4wdrifter said always rotate the engine a few times when complete and double check the timing marks and belt tension.

[newsh]

You might as well align the marks, just stick it in gear and roll it forwards till you see the 0 mark in the bell housing window, takes 30 seconds, then you can check where the other marks are before taking the old belt off.
You need to lock with the proper tool or make one to do the job. Its possible to bend the crank at that torque or do damage to the gearbox, its unlikely the clutch will hold it anyway. Check the key in the pulley and fit a new one if in any doubt, torque to spec using a locking tool. Your valve train depends on it.