Timing check after belt change

[bherman13]

When I put a new timing belt on last year, I made sure everything was set perfectly. Now, obviously, the timing is not perfect because of belt stretch.

My question is, do I need to get timing belt tools again and reset the camshaft? Or is a simple pump adjustment all that's necessary?

I rented the timing belt tools last time so I'd have to find them again to change the camshaft. I wondered if the camshaft timing was affected by belt stretch and if I should readjust it as well.

Thanks!

 

[turbodieseldyke]

Check it first with Vagcom. If it's off, you probably only need to rotate the IP position towards or away from the engine.

 

[Abacus]

There is less belt stretch than you think. The tensioner automatically keeps things spinning as they should be so you won't need to do anything but check the timing occasionally with the Vag-Com.

Unless the timing was set improperly or you have a walking crank sprocket, the lock tools should fit back in at the end of the belt life just as they did upon installation. Prior to changing the belt I always check the timing and have yet to see it off on one done properly the first time.

 

[Vince Waldon]

But... the question is... was the timing checked with VCDS after the initial belt install??

The alignment jigs get you close... in many cases very close... but VCDS is needed to confirm and/or dial it in to "perfect".

 

[bherman13]

When changing the belt, I set the VCDS to default and moved the pump to get as close as I could, then perfected it with VCDS.

Now it's too far off to get back to "perfect" with just VCDS, so I need to readjust the pump.

I was thinking that since the pump has moved just enough to be noticeable, the camshaft timing might be off by that much, too. Obviously not enough to really affect anything much, but maybe a little bit.

 

[Vince Waldon]

Perfect... all good.

I am a little surprised that your pump timing has moved enough to be out of the good zone... so you could check the cam timing just to be sure something else isn't going on.... crank snout wear, for instance. Any obvious wobble of the harmonic balancer?

Most likely everything's fine and tweaking the pump timing is all that's really needed.

 

[annieneff]

When changing the belt, I set the VCDS to default and moved the pump to get as close as I could, then perfected it with VCDS.

Now it's too far off to get back to "perfect" with just VCDS, so I need to readjust the pump.

I was thinking that since the pump has moved just enough to be noticeable, the camshaft timing might be off by that much, too. Obviously not enough to really affect anything much, but maybe a little bit.

The way you describe doing the timing doesn't quite make sense, or maybe I'm misunderstanding what you did.

My understanding is that on the b4, you can only adjust the timing with the injection pump; loosen the bolts and slide it one way or another. What did you adjust in vcds to change the timing?


No way the belt stretched enough to make it go that far out of timing. We'd have to adjust our timing on a schedule if that was the case. Over the lifetime of a timing belt (60,000+/- miles) my timing has never moved, and I check it periodically, and I've gone through several.

It's almost certainly one of the other possibilities. Maybe the bolts holding the pump on weren't tightened all the way. Maybe the crank sprocket is walking. Maybe the cam sprocket isn't tight enough. Maybe the tensioner isn't quite right. Check everything close!

Andrew

 

[bherman13]

I think I was mistaken earlier. It was not too far out of the good zone on VCDS. I had just noticed it moved a couple degrees. I don't know what I was thinking. I readjusted it with VCDS back to about 1.5 BTDC a while back. I just thought I was supposed to set the VCDS in the middle and try to move the pump manually to as close as I can get if I wanted it to be "perfect".

I thought that if belt break-in stretch was responsible for the pump timing to move 1 degree, then it might also be responsible for the cam timing to move 1 degree. I know 1 degree on the camshaft makes a much smaller difference than 1 degree on the pump. I imagine if the cam did move 1 degree, none of us would even notice it. I just wondered if anybody had felt the need to correct for it, or had done so and actually noticed it.

In fact, if belt stretch is responsible for a 1 degree change on the pump, it's likely responsible for 1.5 or 2 degrees on the camshaft since the cam pulley is that much farther from the crank than the pump pulley. Still may not be noticeable though.

Edit: Also, I checked for crank walk when doing the T-belt. I did not see any signs of problems. I also have been running a clutched alternator pulley ever since reading Oilhammer's crank-walk warning.