tensioning cambelt on 2.5 v6 tdi

[almostsuperb]

Hello,

 

I had meant to say that in the newbie bit but a request for some help / advice has beaten me to it...

 

I'm currently working my way through the fun-fest that is the cambelt change on my 2.5 v6 tdi (a BDG version) mk. 1 Superb. After some faff and irritation I am starting to put it all back together - but the process of tensioning the cam/toothed belt doesn't feel right so would appreciate some advice. Am using the manuals I've downloaded from erwin and the Gates info off the interweb. Using VAG parts from TPS.

 

The car is currently is in the following state: lock carrier in service position, crankshaft locked with the Special Tool, new tension and guide pulleys installed along with a new water pump (and also new thermostat and hydraulic tensioning thingy...). Both camshafts are also held with the Flat Plates of Trust; the camshaft sprockets are held on with finger tight bolts (i.e. the sprockets can turn on the coned shafts but not tilt). I have routed the belt as described in the manuals. 

 

I've slowly depressing the hydraulic unit and removed the locking pin but when I try to tension the belt (using a hex key in the hole in the tensioner pulley as indicated in manuals) I get a lot of deflection in the belt - the Gates info (link below, Fig. 13) shows the correct position is when the underside of arm (where the piston from the hydraulic unit touches) and the collar of the hydraulic tensioner unit are parallel (and that's how it was with the old belt) - but I get to this position at 8 - 10 Nm and most definitely into the "incorrect" position (Fig 14) at any more torque. I presume that the "correct position" allows margin in the hydraulic unit to maintain belt tension when it's stretched but that the "incorrect" position does not.

 

Link to Gates info: http://ww2.gates.com/europe/file_display_common.cfm?thispath=Europe/documents_module&file=TB_042_E2_VAG_2.5-V6_TDI.pdf 

 

I have repeatedly checked the orientation of the tension roller - with belt off I've pushed the underside of the tensioning arm to mimic the action of the hydraulic tensioner unit the tensioner pulley gets pushed away from the connecting arm as it should. I'm not sure what else I can check (apart from part numbers - done that!) or can have installed incorrectly - as I see it the tension on the belt is set by its length (and its strength in tension) and the length of the path it's routed through - and the loosely fitted cam sprockets will allow the tension to even out along the length of the belt so avoiding locking in torque on only one leg. 

 

I'm not proceeding any further until I've got this sorted / clear. Is the info in the Gates manual duff / have torque settings changed / any views on what might be amiss if not?

 

Any help much appreciated, James

 

 

 

 

[almostsuperb]

Sorry - ignore all that, I was being over-cautious.

 

Eventually convinced myself that I had the right parts, couldn't have put any pulleys / sprockets in the wrong place, that tensioner pulley was correctly set up and so tensioned the belt to 15 Nm. The hydraulic tensioning pin moved out quite a way but has since slowly retracted back to the "correct" position so all sorted. Relieved and somewhat sheepish...

[Gaz]

Nothing to be sheepish about.  It's not something you want to get wrong.  Glad it's sorted.

 

Gaz