2.5tdi BDH Timing belt tensioer woe

**billybob** · 08-05-2025,11:21 AM

Greetings,

So, at the weekend car cut out when I was slowing for a queue. No nasty noises etc. at the time and I restarted it to pull off the road into a layby. It drove fine under throttle but off throttle the engine died.
Popped the bonnet but not much to check visually apart from the timing belt. However I didn't need to go past that check as the belt was clearly slacker than it should be between the two camshaft sprockets (could easily be pushed out of line by a couple of cm). I got the car brought home by RAC and it's now out front on the road with it's front end off. It looks like the tensioner has failed based on the scoring on the back part of the tensioner pulley. I've seen a timing belt video from continental which shows how the tensioner pulley can wear like due to eventually rubbing against the other piece its attached to if it's been installed incorrectly.

I've actually got the various new tensioner parts in a box somewhere and have the necessary locking tools so nothing to lose by stripping the remaining front down to see if it's possible to swap it in. I guess it will depend on whether the bolt is (a) intact and (b) not cross threaded etc. as I previously read a lot of tales of the thread in the block being a weak spot and people having to mess about trying to re-tap to accommodate a bigger bolt etc. - always sounded like the solutions, if they worked, were less than ideal.

As mentioned, the slackness in the belt was actually between the two cam sprockets as there is little resistance in them so I guess the left hand one ran on a touch longer than the crankshaft after stopping and took up the slack that was caused by the tensioner slacking off. It doesn't seem like it's jumped any teeth though because there are marks on the fuel pump and cam sprockets from where the belt must have been changed the first time and if I apply the tension to the timing belt myself with my hand where the tensioner would normally do it then I can turn the engine manually and these marks all line up still. I've turned it through a couple of revolutions like this and heard a couple of slight tappy sounds from the oil filler hole when first doing this but all quiet on the second revolution.

Assuming I can fit the new tensioner I could just refit the front end somewhat and try the engine and if it seemed ok I could get a new belt on there, but having spent the evening looking through various Russian YouTube videos it feels like I should really have the valve covers off to check for broken or cracked rockers and check that the valves can still be depressed etc. Valve covers and beyond is new territory for me though. Whilst I have done things like timing belts before I have never been fully aware of quite what all the smaller combustion engine internals were and how everything definitively worked prior to last night!

I have a clearer idea now though of the various bits and bobs to check but need to know what needs to be done to get the valve covers off this 2.5 tdi. Looks like some solid fuel pipes run into them. Do these just need to be detached at both ends and removed then block the holes up with something to keep them clean? Any tips? Anything else required? or need to do anything to stop any fuel spills etc? Also, it really looks like I would need to lift the cams out to get a proper look at the rockers etc. as I read comments about how some cracks were only visible after lifting the cams off. I saw a few videos where folk were removing the camshafts but no-one seemed to mark anything so this made me wonder how to know exactly how to put them back exactly the same as you took them out (with regards to the orientation aspect of them if that makes sense?). I'm not averse to doing this if I can get a bit of guidance as I could do with fitting new valve cover gaskets anyway.

I know with these B6's being quite old now there is less activity on the B6 forum than the old days but any help appreciated

Many thanks
Jon

**billybob** · 09-05-2025,11:24 AM

I found an old thread that mentioned what's needed to get the cam covers off and that sounds doable. If I were to remove the cam covers and could not see any obvious damage would there be any reason why I could not apply my manual tension to the timing belt as previously and then turn the crankshaft manually and watch the action of the rockers and valves to at least check for any obvious issues? Would I end up with fuel being thrown about due to fuel pipes being removed?

And as an aside, when I remove the cam covers will I be able to retrieve the rubbery-ish cam cover cap from the rear of the left hand bank fully intact and reuse it? (just thinking ahead to when I need to lock everything when swapping the tensioner over - would be nice not to have to wreck this cap and get a new one as I went straight to locking without taking the cam cover off)

thanks

**Crasher** · 09-05-2025,01:32 PM

I always fit a new bung, good kits come with one. Do you have the locking pin and plates?

**billybob** · 09-05-2025,04:31 PM

Hi, Thanks for the reply Crasher.

Yes I've got pin and plates. Not genuine VAG but a cheaper ebay set. Had to customise the plates a bit with a hacksaw to get them to stay in but they manage to do the job now.
I have a new tensioner already and would buy a new belt if things looked ok under the cam covers so I guess I would look for a bung on its own rather than buy a full kit (everything apart from the tensioner only has 10k miles on it).

I know I would need to wreck the bung getting it off if just doing a straightforward timing belt change where cam covers remain in place but was just wondering if I could salvage it if the cam cover was off. If not re-usable for some reason I think I've seen them sold on their own on ebay or certain continental car parts websites etc. which might be better as I need a few other things like cam cover gaskets, front engine mount rubber bush and the like too

**Crasher** · 09-05-2025,07:06 PM

I have never reused one, just fitted new. Part number 078 103 113 E and £18.30 genuine; Febi 32255 circa £5.

**billybob** · 09-05-2025,07:16 PM

Thanks Crasher. I shall go and find one.

Can you advise if turning the engine by hand with the cam covers off (and thus fuel pipes off too) a no no?

**Crasher** · 09-05-2025,08:01 PM

You may get a little dribble from the ends but not something you should be unused to in advancing years..

**billybob** · 09-05-2025,08:43 PM

Originally Posted by Crasher

You may get a little dribble from the ends but not something you should be unused to in advancing years..

Ha ha. Great stuff, thanks. And you're not wrong about that!

**billybob** · 10-05-2025,10:38 PM

Jeez, those bungs! I know I struggled with it last time but this time is worse. Is there a 'correct' way to get the buggers off? The guidance I have seen previously is along the lines of 'pierce it with something then gradually lever it off'. I had hoped to get to the tensioner today and find out if the thread was knacked but instead I've spent a good 4 hours trying to get that flipping bung out. Managed the piercing after a bit of effort but really struggling on the levering it off part. I expect those who have done many have a good technique / tool. What kind of tool do you use because my selection of screwdrivers really isn't cutting it. I can move any one bit out a couple of mm but it goes back when I move to a different side.