Loose bolts on camshaft pulley cover, rattling engine

[T0MMY]

Hi All, just created an account on here as I've got an issue with my 2018 Leon's 1.4 ecotsi engine which seems to have been mentioned a couple of times on this forum before, e.g. here:

https://www.briskoda.net/forums/topic/517966-loose-bolts-on-camshaft-pulley-just-a-heads-up/

 

Basically, exactly as in that thread, some of the bolts holding the cover plate onto the end of the exhaust camshaft pulley came loose and one disappeared competely, scoring the inside of the belt cover before presumably falling into the belt well.  I retightened the bolts and replaced the missing one but now the engine is very tappety and almost sounds like a diesel.

 

I'm struggling to understand what's causing the engine to run badly now really as the dropped bolt doesn't appear to have fallen into any pulleys as there's no apparent damage to them or the belt and if the timing had been affected in some ways I'd expect a warning light.  The loose cover did leak a small amount of oil but not much.  Any thoughts on this?   I desperately need to sort this quickly as I can't do my job without this car!

Edited 22 May by T0MMY

[Ootohere]

Welcome.

If you had just posted in the thread you linked you might have got a reply.

 

Maybe @ApertureS  or @Crasher  will spot it here now and can help.

[T0MMY]

Apologies, I wasn't sure I should resurrect an old thread.  I did a lot more googling last night and found references to a technical bulletin for this engine suggesting if those bolts come loose (which is common) you should replace the camshaft adjuster as well as loctiting the bolts.  I'm not really clear how the camshaft adjuster works and why the bolts coming loose would cause it to fail (the loss of oil pressure??) but I wonder if that could be causing my symptoms?

[J.R.]

Speculation on my part but it seems to make sense.

 

The bolts come loose because engine oil leaks from the actuator which either softens any thread sealant if it was used or more likely reduces the frictional grip between the flange and pulley allowing it to fret backwards and forwards due to the clearance holes for the bolts, there is no drive dowel and they are not fitted bolts (possibly for timing set up), I am assuming its a clamped flange and not a cover plate, without seeing it I may be wrong.

 

Fitting new bolts does not stop the underlying problem of the oil leak which if severe will prevent the actuator from adjusting the valve timing or maybe its simply the flange having worked loose immediately.

 

It is telling that VAG say the actuator has to be replaced, oil and timing belts are not a good combination, I would remove the belt cover and look again, if there are any signs of fresh oil then replace the actuator ASAP.

[T0MMY]

Well I had another look today and have found the timing belt is slack between the camshaft pulleys, over an inch of up and down movement.  I'm going to assume that isn't meant to be the case right!?

 

My thinking is that the repeated "tug" on the belt as the loose bolt clattered into the timing belt cover on each rotation has knackered the tensioner, is that a reasonable theory?

[Warrior193]

If engine is now thought to be not running as well as previously, it is very possible that the belt has 'jumped' a notch on the pulley - the lost bolt could well have fallen between the belt and pulley when it was displaced. It also sounds as if the tensioner has failed. These issues need to be checked immediately before any further damage occurs.   

Edited 26 May by Warrior193
correction

[T0MMY]

Yes absolutely, I think I've been extremely lucky here, or at least I hope I have.  It's booked in for Thursday at the garage so I'll get the belt and tensioner etc. changed and get them to check the camshaft adjuster.  

[T0MMY]

Just to round this off in case anyone with a similar issue in the future finds this thread, it was indeed the cambelt tensioner.  New belt kit sorted it and it now runs perfectly again so all of the rattle sound was from the tensioner itself or the loose belt.  I also got the exhaust pulley changed just to be safe, although it didn't appear to be damaged.

 

Not very impressed that I came so close to a destroyed engine on a 6 year old car with only 54,000 miles that's never missed a service in its life but I guess I was unlucky (or lucky depending on how you look at it).