Time belt camshaft.

[Anubisxc70]

Hello.
Im thinking on doing myself both of my belts on my XC 70 d5.
I never touched any like this but i have seen the videos on youtube (Thank You Simon) and i just wonder, are the cams shaft and pulleys that easy to move and get out of their marks? Is that easy to turn them?

Im just asking just to have an idea. Are they so easy to move that we cant touch them wile we are taking and putting on the belt?

Many Thanks , sorry for my ignorance.

[canis]

They'll fight you. Although if placed in position they tend to stay put, it's not impossible for them to move given a slight nudge, because the valve springs are very strong. And the sheer effort of getting a belt on is easily enough of a nudge.

The trick is to check and check again. Turn the engine by hand with a spanner or something on the bottom pulley, ensure that the marks line up again after twice around. Do this as many times as you need to satisfy yourself they're correct. DO NOT attempt to start the engine until you've done this.

During this operation you'll feel resistance of compression. Compression feels "bouncy", and eases with effort, but mechanical interferance is not. If you feel mechanical interferance, wind backwards to the start and begin again.

[petey]

Originally Posted by canis

wind backwards to the start and begin again.

Be VERY cautious any time you ever wind an engine backwards. The tensioners on the belt are not always capable of supporting tension correctly when the engine winds backwards and they can slip.
You need to have two full turns of the CAMSHAFT (four turns of the crank) before you could ever consider thinking about perhaps maybe starting the engine. I would suggest that leaving the car in top gear and winding the right front wheel forwards is the easiest way. Put a block of wood under the left hand front wheel if you have jacked up the whole of the front. Take it out of gear before starting the engine.

If you, for whatever reason at all, wind the engine backwards, then go forwards again the full amount. Do not ever be tempted to go backwards deliberately; if you overshoot your timing marks, go round again and take more time next time.

It's a very simple process, and actually reasonably hard to get hopelessly wrong, but the consequences of doing so are VERY expensive.

[canis]

Originally Posted by petey

If you, for whatever reason at all, wind the engine backwards, then go forwards again the full amount. Do not ever be tempted to go backwards deliberately; if you overshoot your timing marks, go round again and take more time next time.

This sounds confusing.

Yes, it's true you shouldn't wind an engine backwards, but if you're experiencing mechanical resistance you don't really have any choice. You can't go on any further and MUST NOT TRY. Wind it back to the beginning, then DO NOT "attempt to go forwards the full amount", but take the belt off, re-align everything and begin again from scratch.

If you simply overshoot, yes, go round again.

[TDIvolvo]

Originally Posted by canis

If you feel mechanical interference, wind backwards to the start and begin again.

No, never ever do this, admit defeat and go round again!

EDIT: I misread this line - I just saw the wind if backwards bit standing out like a sore thumb. Never wind an engine backwards - if you balls it up like this then you should really reset it all and start again but not by winding it all the way back.

[JGTTDI]

Quite simply, if you are not 100% confident on replacing the belt just pay someone else to do it. It is not worth potentially ruining the engine by just giving it a go. That being said it isn't a very hard job to undertake yourself but if in doubt just pay someone else.

[canis]

Originally Posted by TDIvolvo

No, never ever do this, admit defeat and go round again!

And how are you gonna do that?

Oh... whatever...

[petey]

Originally Posted by canis

And how are you gonna do that?

Oh... whatever...

Obviously you can’t force a mechanical clash, but if you know enough to be changing a belt, then you should not be getting this problem. If you don’t know how to avoid the mechanical clash, pay someone because it’s easy to rack up a big bill.

For the avoidance of doubt, if you align the timing marks then disconnect the belt, winding the crank back will make sure no matter what you do the cam, you’ll still be safe. Only wind the crank back when you’re certain it’ll be correct and then fit the belt

[TDIvolvo]

Originally Posted by canis

And how are you going do that?

Oh... whatever...

No don't be flippant. I reacted so quickly when I read your comment that I didn't read it in context - for that I do apologise - my fault.

I understand now, your comment is assuming utter muppetry has been deployed and there is a mistake to the extent that there is now a mechanical clash - OK yes perhaps if this had happened moving it back a little might be the answer but to be honest if this has happened then I would not be rotating the system as a whole at all. I would be taking note of all the sprocket positions and I would be taking the belt off for a complete re-time. Little point in doing anything else because you are going to need to re-time it anyway.