1.9TDI 90 bhp AGR. Reading through the Haines 'cam belt removal/refit' process it says the three 'stretch ' bolts securing the injection pump sprocket should be replaced. Does the sprocket need to be removed ? The manual doesn't give a reason. I can only think that the sprocket should be free to turn when the belt is tensioned to evenly remove the slack. Has anyone else done this job and followed this procedure ?

You shouldn't have to touch the bolts on the pump pulley, they are there as a means of adjusting the pump timing. To preseve the timing, the marks on the flywheel and cam should be lined up and preferably the cam locked and the pump locked with a pin before removing the old belt.

You should really replace the engine mounting bolts.

I think official procedure is to adjust the timing with VAG-COM or the dealer computer, replacing the bolts one by one after the timing is set by temporarily re-using the old ones.

I doubt anyone bothers, and they probably do as fordfan says.

CAr Mechanics Mag this month has a section on changing a cam belt on an OCTY. No need to disturb the pump mounting but be sure to lock the pump & cam from rotating before the change

CAr Mechanics Mag this month has a section on changing a cam belt on an OCTY. No need to disturb the pump mounting but be sure to lock the pump & cam from rotating before the change

There is if the pump timing needs to be altered after it is check dynamically.

Thanks for the replies. I've changed quite a few cam belts in my time, the most involved being a Sharan TDI Mk1. The Octavia TDI Mk1 with AGR engine being very similar. I'm still not convinced that the Injection pump sprocket bolts don't need to be slackened. From the manual it implies that the pump locking pin locates through a hole in the sprocket (larger than the locking pin) and locks the pump leaving the sprocket to move slightley when the belt is tensioned, hence the elongated holes. In that way the pump spocket turns slightly as belt slack is taken up and the pump timing is preserved by the locking pin. Am I wrong on this or is it just that others don't bother ?

AFAICS, the only mention of the injection pump sprocket in the info I have is:

- Lock injection pump. Use tool no. 3359.

- Slacken injection pump sprockets - NOTE: DO NOT slacken injection pump centre hub nut.

...and during refitting I have:

- Remove bolts from injection pump sprocket. Fit new bolts.

- Align injection pump sprocket with bolts in centre of slotted holes.

...then:

- Fit timing belt in following order: crankshaft sprocket; guide pulley G1; water pump sprocket; injection pump sprocket; guide pulley G2; tensioner pulley; guide pulley G3.

...then:

- Temporarily tighten injection pump sprockets to 20Nm - NOTE: DO NOT tighten further 90deg.

...then:

- Ensure locking pin can be inserted in injection pump. Tighten bolts further 90deg.

- If not: turn crankshaft until locking pin can be inserted - tool no. 3359; slacken injection pump sprocket bolts; turn crankshaft to TDC on no. 1 cylinder; ensure timing marks aligned; tighten to 20Nm + 90deg

Probably doesn't make much sense without the rest of the instructions, but at least the sprocket can stay in situ. As for the engine mounting bolts, there is mention of removing and re-fitting them, so I presume you'd use new-for-old as you would for most other things like that...

From the manual it implies that the pump locking pin locates through a hole in the sprocket (larger than the locking pin) and locks the pump leaving the sprocket to move slightley when the belt is tensioned, hence the elongated holes. In that way the pump spocket turns slightly as belt slack is taken up and the pump timing is preserved by the locking pin. Am I wrong on this or is it just that others don't bother ?

This is correct - and the same for the camshaft - and it's how a Skoda dealer did mine. It allows for new belt to be a slightly different length, or for water pump or idler pulleys to be in slightly different positions after replacement. But then with the injection pump you're meant to start it up & use diagnostic computer to check the actual timing whilst it's running. If that's out, you loosen the bolts again, turn the pump slightly in whichever direction, tighten them again & repeat until it's correct.

I don't think the dealer bothered with checking the dynamic timing for mine & it came up as too advanced when I checked in on VAG com. So I took it back, and this time they set it too retarded (they forgot to go into "Basic Settings"). Third time round they actually got it in spec!

Edited 7 November, 200817 yr by AJB