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[JamesV6CDX]

I changed the cambelt on one of my Omegas today.

When I removed the cambelt cover, and looked at the setup, I found this.

Can any eagle eyed OOF'ers spot what I'm talking about? (Clue, it's not a timing issue).

I wonder what the potential implications of this are.

It's corrected, now, and sporting a new kit, so good for the next 40k / 4 years

[Kevin Wood]

The orientation of the sprung idler looks a bit odd to me. Been tightened the wrong way to take the slack out?

[Shackeng]

There is something odd at 7'o'clock behind the red cam wheel.

[Migv6 le Frog Fan]

Its a while since I did one, and my memory is fickin shockin, but aren't the idler/tensioner the wrong way round. I.e. each one should be where the other one is ? 

[cam.in.head]

i take it you are referring to the earlier central top centre pulley style rather than the offset 2.6 3.2 type . or am i missing something other

[STEMO]

You left the locking tools in.

[Doctor Gollum]

Cracked rear cover next to alternator?

[Kevin Wood]

Hmm, and the shoulder on the bolt securing the bottom idler doesn't look like it's seated in the bore in the central part of the pulley.

[JamesV6CDX]

Hmm, and the shoulder on the bolt securing the bottom idler doesn't look like it's seated in the bore in the central part of the pulley.

Bingo - nail on the head

[JamesV6CDX]

So, looking closer up.

What has happened, is that one of the E14 headed bolts (for securing the tensioner backplate) has been used in the bottom idler.

The correct idler bolt (with the smaller E12 headed bolt) has been used on the backplate.

The thread, length, and pitch of these bolts are actually the same, but, due to the larger head on the E14 one, you can see below, it doesn't fit properly into the bore of the idler:



As a result, because it doesn't go into it's recess, the amount of thread protruding from the rear of the idler, is somewhat less:



Not sure what the implications of this could have been - if any

I wonder how effectively the head of the bold was securing the idler, on the basis that, not being in the bore, it doesn't actually have much area to purchase on (on the idler face)

It's an academic question, because I've corrected it all - I'm only asking 'cos I'm curious

[STEMO]

Hmm, and the shoulder on the bolt securing the bottom idler doesn't look like it's seated in the bore in the central part of the pulley.

That was well spotted, Kevin 

[Andy H]

I don't like the angle of the top tensioner - belt tension should try to turn the tensioner clockwise (which would cause the centre bolt to tighten if it ever did move). That tensioner looks as though it is ready to go the other way and loosen the centre bolt - it looks as though there is one tooth too many on the belt between cam 2 & cam 3.

If there is one tooth too many between cam 2 & cam 3 then it will be one tooth short on the run over the spring loaded tensioner - which might explain why the orientation of that idler looks odd.

[Kevin Wood]

I don't like the angle of the top tensioner - belt tension should try to turn the tensioner clockwise (which would cause the centre bolt to tighten if it ever did move). That tensioner looks as though it is ready to go the other way and loosen the centre bolt - it looks as though there is one tooth too many on the belt between cam 2 & cam 3.

If there is one tooth too many between cam 2 & cam 3 then it will be one tooth short on the run over the spring loaded tensioner - which might explain why the orientation of that idler looks odd.

Yep, that's also true.

[Kevin Wood]

So, looking closer up.

What has happened, is that one of the E14 headed bolts (for securing the tensioner backplate) has been used in the bottom idler.

The correct idler bolt (with the smaller E12 headed bolt) has been used on the backplate.

The thread, length, and pitch of these bolts are actually the same, but, due to the larger head on the E14 one, you can see below, it doesn't fit properly into the bore of the idler:



As a result, because it doesn't go into it's recess, the amount of thread protruding from the rear of the idler, is somewhat less:



Not sure what the implications of this could have been - if any

I wonder how effectively the head of the bold was securing the idler, on the basis that, not being in the bore, it doesn't actually have much area to purchase on (on the idler face)

It's an academic question, because I've corrected it all - I'm only asking 'cos I'm curious

With far less thread engaged but presumably the same torque applied (but, let's face it, on this job, probably just a couple of grunts) the bolt would have been much closer to failing. The smaller clamping area on the pulley would have done it no favours either. That could very well have ended in tears. Good job you got there first.

[JamesV6CDX]

I don't like the angle of the top tensioner - belt tension should try to turn the tensioner clockwise (which would cause the centre bolt to tighten if it ever did move). That tensioner looks as though it is ready to go the other way and loosen the centre bolt - it looks as though there is one tooth too many on the belt between cam 2 & cam 3.

If there is one tooth too many between cam 2 & cam 3 then it will be one tooth short on the run over the spring loaded tensioner - which might explain why the orientation of that idler looks odd.

That could potentially explain why, the timing marks all lined up, but the tensioner mark was below where it should be

[Doctor Gollum]

Who changed it last?

[JamesV6CDX]

Not me, thank goodness!

Without wanting to sound like a knob, I'd rather not go into that, if that's ok - which is why I didn't mention which car it was etc.

I just posted for a bit of fun, to see if anyone could spot it, and to enquire as to what the result could have been

[Viral_Jim]

On that specific point, potentially the tensioner not running true to the belt- causing wear on one side maybe? Also, given the very few threads protruding from the back of the tensioner, I wouldn’t have been amazed if it had worked itself loose and thrown the tensioner  . Maybe that’s being overly dramatic though.

I once did a timing belt on a Mk 5 escort 1.6, stripped it down and found that the fitted belt was smaller than the replacement one and that no tensioner was fitted  . Bizarre. How it run is a mystery to me.

[JamesV6CDX]

Also, given the very few threads protruding from the back of the tensioner, I wouldn’t have been amazed if it had worked itself loose and thrown the tensioner 

Now you mention it, I undid the bolt using a short ratchet, requiring next to no effort, so it certainly wasn't holding the required 40nm. Whether it's worked loose due to the incorrect bolt length, or wasn't tightened sufficiently from the outset, are of course unknowns

[Nick W]

Who changed it last?

if it's one of Tony's cars, then I did.

[Marks DTM Calib]

On that specific point, potentially the tensioner not running true to the belt- causing wear on one side maybe? Also, given the very few threads protruding from the back of the tensioner, I wouldn’t have been amazed if it had worked itself loose and thrown the tensioner  . Maybe that’s being overly dramatic though.

I once did a timing belt on a Mk 5 escort 1.6, stripped it down and found that the fitted belt was smaller than the replacement one and that no tensioner was fitted  . Bizarre. How it run is a mystery to me.

The friction to hold the idler in place is from the idler to mounting surface, the bolt should, in theory still be to the same tightness as the reaction torque which you tighten against is from the threads....there is just less of them so the force on the threads is greater.

[Nick W]

On that specific point, potentially the tensioner not running true to the belt- causing wear on one side maybe? Also, given the very few threads protruding from the back of the tensioner, I wouldn’t have been amazed if it had worked itself loose and thrown the tensioner  . Maybe that’s being overly dramatic though.

Any threads protruding from the back of a female thread are not contributing to the clamping action. So it makes no difference if there are 3 or 30. It's a similar case in a blind hole; only the first few threads near the joint are actually doing anything.


I'm more concerned about not noticing that the head didn't fit the counterbore

[JamesV6CDX]

I'm more concerned about not noticing that the head didn't fit the counterbore

Mate, I wouldn't worry, we're all human. I wasn't even going to say which car it was, I knew it would have been an honest mistake. I was 50/50 if anyone would even be able to spot it from the pics.

Makes me think back to some mistakes that I've made, in the past - there've been a few.

The one that makes me laugh the most, was doing an oil change on a VW, I fitted the filter, poured the new stuff in... checked the dipstick.... hmmm........ nothing..

Yep, I hadn't put the sump plug back in  Thank god I realised before trying to start it 

I also once took a short cut and changed a failed V6 water pump without removing the outer cover. Can be done, with the right sockets.....as has been documented on here before. Really didn't see an issue with it -  but unbeknown to me, during its failure, the old pump had deposited loads of small bearings in the cambelt setup, which threw the belt two teeth a while  later.

Never again - it always comes right apart for inspection now 

Thankfully, I was able to recover it with no damage done, but it was a bum squeaker!