Cam-belt replacement - is this acceptable way?

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Cam-belt replacement - is this acceptable way?

Postby brookie » 21 Jul 2011, 10:16

When I replaced the cam-belt and tensioner on my AAZ 1.9td van the first time I managed to do it successfully by lining up TDC mark on flywheel and painting white markers on cam and fuel pump sprockets to line up with painted marks on cam housing and fuel pump. Everywhere I read it states I should be locking the fuel pump with a pin and the camshaft using a special tool and equal amounts of feeler gauges to ensure everything's at TDC.
That's all well and good but if a new belt goes back on in EXACTLY the same sprocket positions what is the difference? Have I just been lucky or is there a very high chance that my valve timing is out? :(
In one text of 'Cam belt replacement' (Haynes Golf AAZ)it says about loosening camshaft sprocket bolt and tap off the sprocket so as to align sprocket to belt whilst camshaft is held stationary in TDC. I have never done that and my understanding is that there's a woodruff key on shaft to align with the sprocket so how can the sprocket be rotated independently of shaft? :?
It confuses the hell out of me, is my method gash?! Is Haynes assuming a complete rebuild from scratch and what's with the turning of a keyed sprocket on a keyed shaft? :? :? :?
Really appreciate any helpful answers as all my friends run petrol vans and my wife just gives me a 1000yd stare when I mention it to her!
1986 High-top 1.9 Td called Scooby
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Re: Cam-belt replacement - is this acceptable way?

Postby camper » 21 Jul 2011, 10:43

There is no woodruff key on the camshaft taper.When the cambelt is tensioned after fitment the loose cam sprocket will turn on the taper with out effecting the cam shaft timing.The idea then is to tighten up the cam sprocket bolt .Set the engine at TDC lock the fuel pump with a pin the camshaft has a slot at the rear where a plate can slide into it.At TDC the pin for the pump&the plate for the camshaft with the cam sprocket undone on the taper can have the cambelt removed or replaced when the tensioner is released.Oh dont be confused by the taper as it is a interference fit only for the cambelt to be tensioned then a bolt is tightened to the sprocket if it had a woodruff key it would move the camshaft out of timing position.
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Re: Cam-belt replacement - is this acceptable way?

Postby brookie » 21 Jul 2011, 11:26

If there's no woodfuff key on it then all is clear and thanks for the info. I don't know what Haynes is on about as they mention this keyway and if it's not there they mention a lug in the sprocket has to line up with recess in camshaft. Perhaps they're referring to the ADZ,ADY,AAM,ABS and 2E engines not AAZ but they don't specify. You have certainly helped!
I am now concerned that my timing is slightly out as it could have been out before I replaced it! :(
1986 High-top 1.9 Td called Scooby
brookie
 
Posts: 30
Joined: 1st, Dec 2005
Location: Ringwood,at the edge of New Forest
80-90 Mem No: 5394

Re: Cam-belt replacement - is this acceptable way?

Postby camper » 21 Jul 2011, 11:39

Regarding the cam sprocket taper there is key slot cut into it but there is no woodruff key to fit the taper or sprocket for diesel engines.So if you decide to undo the bolt make sure you hold the sprocket end with a tool whilst undoing but not the cam plate locking end.Because you can break the cam shaft .When you loosen the bolt give the sprocket a thump with a rubber hammer or a light tap with care to break the interference fit between the sprocket&taper
camper
 
Posts: 360
Joined: 30th, Oct 2005
Location: Bookham Surrey
80-90 Mem No: 1710


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