Timing Belt Procedure Volkswagen LT

[volkswagen]

Having been flushed with the success of the starter motor and crank pulley replacements and the dreaded fuel filter change, I'm considering attempting the timing belt swap. At a garage the timing belt change costs £500+, and, at the moment, there is a special offer on parts meaning that I can get the entire kit (inc water pump) for £85.

I've read through the procedure and it seems straight forward enough (I've done a few before), but I'm puzzled why you have to loosen the camshaft sprocket from it's shaft. The ones I've done before, you either lock the sprockets with a special tool or drill bit, or you mark the positions of the sprockets and make sure they don't move.

Is it really necessary to loosen the sprocket as it would make the job a lot harder and more scope to go wrong.

 

[Burnerman]

I don't bother slackening any of the sprockets - although the day may come when its necessary, I haven't found one yet!
Plenty of dabs of white marker and slacken off all tensioners is the way to go for me.
To date, I haven't used force on any belt at all to get it where its supposed to go.
I draw a blank at those engines which don't have keyed crank pulleys though - too much faff to buy all the locking gear.
John

 

[volkswagen]

Thanks john.

So it's just a matter of making the belt easier to fit. I thought there was more to it than that.

The procedure does seem a little confusing, for example, the camshaft tdc is set and locked by feeler gauges, yet the crank tdc is set by the naked eye from the flywheel with no way of locking, the mark could be out a couple of mm each way.

 

[Burnerman]

It sure looks a complex one, but the way I look at it, if the belt is simply replaced with a new one, and no pulleys are moved at all then all should be well!
The crank pulley is set with the mark at the bottom, and there should be a datum mark on the pulley itself.
If in doubt I would leave it to a specialist - the book time is over 4 hours, and thats for those who have done it before!
John

 

[volkswagen]

Thanks again, John.

I suppose it's £500 for a reason.

 

[absoft]

The way to do it is tippex the old belt, camshaft and crankshaft sprocket before you take the old belt off. Then lay the new belt above the old belt and apply tippex in exactly the same two places on the new belt (assuming its not twin cam when there would be three marks). Then simply align the new belt marks with the marks on the cam and crank sprocket. You can't go wrong and no need to even find any timing marks or lock anything. Works for me everytime EXCEPT if you have one of those silly engines that don't key the pulley to the crankshaft like the ford zetec. Also if it is a diesel, you'll need to mark the pump if driven by the timing belt.

You'll also need a decent impact wrench to undo the pulley bolt and do it up again. I use a Clarke mains one. You can get by by using a spanner on the pulley nut, wedging it and blipping the starter with the ignition disabled assuming the engine turns clockwise. The do it up in gear with someone applying the brakes.

 

[volkswagen]

Thanks absoft. Genuine Vauxhall belts come with yellow lines on them which you line up with marks on the sprockets and engine, so your idea is well proven. The crank pulley is not keyed to the shaft, however, there are four torx bolts which, along with the main bolt, fasten it to the sprocket which has a woodruff key. I've had the crank pulley off to replace it, I used a 3/4 breaker bar and a scaffold pole with someone holding the brake.

 

[AlanE]

If you think about it logically there is a reason why one of the sprockets is adjustable.

Not sure about your vehicle but on my Peugeot 406 HDi the crank one is keyed but it is a 'slack' fit.

When changing the belt on this the crankshaft is pinned as is the camshaft pulley so the timing has to be correct.

The reason for the adjustable pulley is down to tolerances. The belt drives a number of items and has to tensioned a certain amount but the tensioner is only on one side of the belt. Now without any adjustment around the belts path one side would be tensioned correctly while the other sides may not.

As soon as the locking pins are removed to equalise the tension the cam would become offset from the crank, only by a very small amount admittedly but the timing would still be out slightly.

With one pulley slightly adjustable when the belt is tensioned that tension would equalise around its circumference but, because the cam and crank are both locked in their reference positions that position, in relation to both crank and cam is still 100% perfect when the locking pins are removed.

This adjustment procedure is basically to compensate for, maybe minute, but differences between belt manufacturers.

 

[absoft]

Hi AlanE, yeah I was thinking about that and came to the conclusion you describe. Apparently the cam is not keyed on this VW. However so long as the crankshaft is, I'd be inclined to just mark up the belts and put the new one on without loosening the cam sprocket at all. There's hardly going to be any difference and if there was, it might change as the new belt stretches a little.
So far I've only ever changed belts on cars where everything is keyed in with woodruff keys so you are either a tooth out or bang on. There is no finer adjustment.

 

[AlanE]

Again don't know with other vehicles but the HDi has a cam position sensor and a crank position sensor both feeding information to the engine management system so 'slightly out' might be a bit too far out when it comes to cold starting or fuel economy, don't know.

What does need thinking about is why do the manufacturers do it if it wasn't really necessary?

I used to repair TV's years ago and a certain manufacturer, after having a new model out in the field for a short while, produced the 'cost improved' version. A few wires cut a bit shorter, components de-rated etc. may only have saves pennies on each set but a million pennies soon adds up!

Same with car manufacturers how much could they save by only having fixed pulleys? Soon mounts up so they definitely consider it necessary and to be honest when I changed my belt had no problems setting it up first time with the adjustable crank pulley.

 

[Belle427]

which engine does it have?

 

[volkswagen]

I see what you mean, Alan. With the cam pulley loosened, the belt is 'pulled' around the pulley, tensioning the entire belt.

To explain, I'm not trying to cut corners with the job, but the locking procedure is unclear. The engine fitted to my van is a variation of the old Audi R5 2.5 Tdi. My version is the BFF, the final revision before the engine was completely reworked for the Crafter. The earlier versions camshaft was locked by removing the camshaft cover and rear injection pump pulley, and inserting a locking bar into a groove machined into the end of the camshaft, centring it onto the cylinder head using feeler gauges.

The BFF and other later engines have the inlet manifold crossing from one side of the engine, over the head and back down the other side. This prevents removal of the camshaft cover without at least taking off the manifold and a few other bits. I know that the VW van centre didn't remove the head the last time it was done and Elsawin (VW dealers workshop manual) removes the locking procedure for my engine, so I'm unsure how it is done.

 

[Belle427]

I can only see a BBF 2.5tdi engine on autodata and it looks pretty complex.
Suggests the use of a dti on the injection pump some how when setting up!

 

[absoft]

Volkswagon - you can either do this by the book which will be rather complex, take you longer, and cost you more for locking tools; or just white-up everything and replace existing belt with a new one which is what I guess most garages do that offer you a cheaper quote. The belt will be tensioned fine because as you tension the belt, the cam and crank will move slightly anyway so BOTH sides of the belt WILL be tensioned if you haven't used any locking tools.

 

[volkswagen]

Sorry ch427, I meant BBF , surprisingly, came right after BBE .

The injection pump set up is one part of the job where I know what the garages do: You mark the pulleys before removing them which gives you a rough timing then use VCDS/vagcom to fine tune. If you haven't got the program, then you have to use the dti.

I know what you mean absoft, if neither the cam or crank are locked up, the pulleys will move slightly as the tension is applied. As you say, there's more room for problems if I start loosening stuff without properly locking the camshaft.