Polo tdi cambelt change

hamburg

just want to ask a question here and hopefully someone knows the answer. I am going to change the cam belt and water pump on a 05 1.4 TDI polo and it looks straightforward enough. I have changed a few cam belts before but this is the first pumpe duse I have tackled.anyway I was looking at few YouTube video's on the subject and in everyone of them, before they loosen off the belt tensioner,they loosen off the 3 bolts on the camshaft sprocket and move the sprocket back and forward and then nip the 3 bolts back up. Then they remove old belt and water pump and fit new belt and pump. I should mention that at very start the engine is put on its timing marks and special locking pins are inserted in the crank and cam pulleys to lock the engine safely to its timing marks. But for the life of me I cannot fathom or find out why the camshaft sprocket is loosened up and moved back and forth? Can some knowledgeable person explain this to me? Thank you !

MaryAntoinette

This is a classic example of why you should not trust you tube videos.

hamburg

MaryAntoinette wrote: »

This is a classic example of why you should not trust you tube videos.

meaning?

MaryAntoinette

Do not go messing with loosening the 3 bolts on sprocket, tbh I would not be relying on any youtube video to change a cam belt.

hamburg

MaryAntoinette wrote: »

Do not go messing with loosening the 3 bolts on sprocket, tbh I would not be relying on any youtube video to change a cam belt.

I should point out that one of these video's is actually an official skf how to video on a 1.9 Passat and they loosen the 3 camshaft bolts and wiggle it to and fro.there is no explanation though why it is done? So if skf ,probably one of the top manufacturers of timing belt kits are showing it being done in one of their videos,it must need to be done! I just wish they would say why it is being done! I also found an official vw online workshop manual and they tell you to loosen the 3 bolts when doing the belt but they don't say why!it just puzzles me.

jca

Is it the case that the locking pin goes through the camshaft itself, then when you thread the belt around the crankshaft sprocket making your way up to the camshaft and the teeth on the camshaft pulley don't line up exactly you can move the pulley slightly to get the belt to slide on. I'm sure this is obvious to you but don't loosen those three bolts until you have the locking pins in the crankshaft and camshaft.

rex-x

MaryAntoinette wrote: »

Do not go messing with loosening the 3 bolts on sprocket, tbh I would not be relying on any youtube video to change a cam belt.

You have no idea what you are talking about

hamburg

Yeah I got the locking pin kit. I wasn't going to attempt it without it.i might ring Vw later on and ask them what the story is .

jca

hamburg wrote: »

Yeah I got the locking pin kit. I wasn't going to attempt it without it.i might ring Vw later on and ask them what the story is .

There's no need to ring VW it'll all become very obvious when you're doing it, as I explained in my earlier post the locking pin for the camshaft passes through the camshaft pulley without touching it and locks the camshaft directly. Loosening the three pulley bolts with the camshaft locked allows you to move the pulley left or right to allow the new belt to be slipped on without altering the timing by even the tiniest bit.

hamburg

jca wrote: »

There's no need to ring VW it'll all become very obvious when you're doing it, as I explained in my earlier post the locking pin for the camshaft passes through the camshaft pulley without touching it and locks the camshaft directly. Loosening the three pulley bolts with the camshaft locked allows you to move the pulley left or right to allow the new belt to be slipped on without altering the timing by even the tiniest bit.

Right, I got an answer to this from a skoda mechanic. Basically by loosening the 3 bolts you can advance or retard camshaft timing by going clockwise or anti clockwise.this is supposed to be adjusted every cam belt change as the cam belt over the course of its life can stretch ever so slightly and affect the cam timing. This guy says that ideally it should be set with the Vw vcds computer system after the new belt is fitted by loosening the 3 bolts slightly and then put a spanner on the big center bolt of the cam sprocket and tap it a mm or so right or left to advance or retard the cam timing. Which ever way the vcds says it needs to go.then they tighten the 3 bolts, start the car and recheck the timing values via the computer.then if it is fine the leave it alone or if it is not they loosen the bolts again and fine tune it.

jca

I never heard of it being used that way, I wonder how vcds measures cam timing? When I got my belt changed on my 1.9 TDI the mechanic had to loosen the three bolts and move the pulley around the shaft slightly to get the teeth to align exactly. The same result really just done old school I suppose. I'm intrigued as to how vcds knows, I'm surprised my mechanic didn't do it that way.

hamburg

This guy told me to google torsion values or torsional values. I googled it but truth be told most of it went over my head.😄

Waterson

rex-x wrote:

You have no idea what you are talking about

The skoda mechanic is pretty much on the money with his description. The adjustable cam pulley is designed to take up the stretch in the cambelt over time. The vcds would use the camshaft position sensor feedback when adjusting cam timing. Provided when you fit the new belt there is very little deflection in the belt on its longest run, i.e. between the cam and crank pulleys and the 3 cam pulley bolts aren't resting at their stops or the extreme ends of their holes, you should be fine.

hamburg

Waterson wrote: »

The skoda mechanic is pretty much on the money with his description. The adjustable cam pulley is designed to take up the stretch in the cambelt over time. The vcds would use the camshaft position sensor feedback when adjusting cam timing. Provided when you fit the new belt there is very little deflection in the belt on its longest run, i.e. between the cam and crank pulleys and the 3 cam pulley bolts aren't resting at their stops or the extreme ends of their holes, you should be fine.

What do you mean "make sure the bolts aren't resting at their stops?

jca

hamburg wrote: »

What do you mean "make sure the bolts aren't resting at their stops?

He means that the bolts are approximately in the centre of the elongated slots not at either end leaving you no room for manoeuvre if you need it.

hamburg

Well I done this job and honestly it went handily enough. The stripping down to actually get to the belt was more hassle than removing the old belt and pump and fitting the new one's. That said I would really recommend buying the engine locking tools before attempting this.There are probably people out there that could do it without using the locking tools, but I wasn't that brave. Anyway it is done. Thanks for all the advice!

jca

Fair play to ya well done. You did right getting the locking kit the tolerances are too tight for any guesswork. Did you have to loosen the three bolts on the camshaft pulley?

hamburg

jca wrote: »

Fair play to ya well done. You did right getting the locking kit the tolerances are too tight for any guesswork. Did you have to loosen the three bolts on the camshaft pulley?

yes I loosened them, to say I was sweating bullets is putting it mildly,but the cam locking pin kept everything dead on. I still must have checked all the timing marks about 50 million times though! The old water pump bearing felt and sounded grand,as did the old idler pulley but the old tensioner bearing felt as rough as badger ar$e when I spun it! All changed now, thank god.