Gti6 Cam Sprockets

[2052006 10]

So I removed both camshaft sprockets on my gti6 engine, in order to remove the inner cam belt cover. Obviously, it was all timed up before hand. However, when I removed the sprockets the inner part with the "key" and the timing hole came with the sprocket (this is the part that the sprocket moves around on when tensioning the belt - I don't know the correct name of it!).

 

Whilst the inlet cam didn't move when I did this, the exhaust cam did spring forward (clockwise direction) a few degrees. I don't think this should really be a problem should it, so long as I move it back and make sure it's timed up properly?

 

Am I right in saying that any valves would have moved "up", i.e. back into the head, rather than down, with this movement?

[2052006 10]

Any thoughts? Or have I not described it very well?!

[Anthony 1,003]

So long as the engine was in the timed up position before hand (so pistons halfway down the bores) it should be fine and the valves/pistons not touched - one of the cams in a GTi-6 has a habit of wanting to ping round a few degrees if you don't have a timing peg in it.

 

Just make sure that you rotate the cam back a touch so it all lines up again when fitting the belt, otherwise it likely will go horribly wrong when you turn it over...

[unariciflocos 49 1 Cars]

Just imagining this in my head with the asumpion that lobes are 90 deg apart... 2 lobes will have been fully vertical on their lifters so they slipped 45 deg either to one side or another. That means that you had 2 vales fully open and now you have 4 partially open. If by any chance the two valves that were fully open caught the other side vales in a partially open position they may have clipped them.

 

Chances are there will be no damage, just be careful when turning the cam back. Just like with Q-tips, if there's resistance, stop. If there was damage, you'll hear it when you turn the engine on.

[2052006 10]

Just imagining this in my head with the asumpion that lobes are 90 deg apart... 2 lobes will have been fully vertical on their lifters so they slipped 45 deg either to one side or another. That means that you had 2 vales fully open and now you have 4 partially open. If by any chance the two valves that were fully open caught the other side vales in a partially open position they may have clipped them.

 

Chances are there will be no damage, just be careful when turning the cam back. Just like with Q-tips, if there's resistance, stop. If there was damage, you'll hear it when you turn the engine on.

This is what I was wondering. As Anthony says, there won't have been any valve/piston contact, but was wondering if it was at all possible for the inlet/exhaust valves to clip each other under these circumstances?

[JeffR 51]

Note the position of the woodruff keys. These are the positions the cams need to be in when the belt is off (and you've correctly set the static position with the pistons half way down the bore).

 

Fit the cam gears & rotate the cams until you can lock them again, fit the belt, rotate engine 720° and make sure you can re-pin the crank & both cams.

[2052006 10]

Did this today, successfully, (I think), no apparent problems with the cams or timing.

 

However, one of the problems I had with my old belt (one which I just fitted recently), was that it was rubbing on the inside of the crank pulley (a light weight aluminium one). This meant that it was damaging the side of the belt to the "outside" - which was plainly visible. Tbh, I can't remember how far I had pushed it on to the crank sprocket that time, it may just have been my error.

 

So I fitted another one today and tried to line it up on the crank sprocket centrally. However, having run the engine up to temp a few times, I'm sure the belt is moving ever so slightly to the "outside" again. Whereas it was, for example, sitting centrally on the pulley and tensioner pulley, it's now moved a fraction towards the outside of these pulleys. It's not hitting the inside of the crank pulley (yet), but I'm concerned it will.

 

Are these cam belts meant to move a little, in this way, after fitting. Do they take a little time to "seat" as it were. Or have I got an issue here? Don't want to destroy another belt!

Edited November 1, 2014 by 2052006

[welshpug 1,657]

check the tensioner stud is not bent and the idler bolt is clamping correctly, I have come across idler bolts which bottomed out in the block before clamping the pulley fully which would cause it to sit on the piss.

 

never ran the engines as I spotted it well before assembly so not see what they would do, but its the kind of thing that would cause it, also check the water pump.

[2052006 10]

Was thinking it might be something like this. Brand new Valeo pump though, and new Dayco tensioner and idler. I will check the stud though and also idler bolt. IIRC, I had to use the old idler bolt, as the one in the kit didn't fit. Or something like that, pity I can't remember, it was months ago that I first fitted it. Bollocks, going to have to remove the belt again, argh!