Help With Timing Belt Tensioner

[Andmcit]

Hohum!

My timing tensioner has run it's bearing out and collapsed allowing the belt to unravel whilst
I was driving. In hindight I realise now a noise that had just developed was the tensioner/idler
rather than the hydraulic pump I thought it was...

Anyhow, damage limitation exercise coming into effect!! First off - does anyone know if the
valves are clear of the piston in such a scenario or is there overlap?

Next off, as GSF dont directly list any Xm tensioner, does anyone know if it's the same as
the Xantia 2.0i 8v as there is a listing?

Andrew

[dean]

Hi Andrew

I got a cam belt kit with tensioner from Unipart for £40, don't know how this compares with gsf, but the did list it as an xm engine so you are guaranteed to get a bit that will fit, Just depends if you have a branch near you.
As regards your valves i would imagine they are dead but this happened to me a few times now with old bangers. Even so i usually get the belt back on wind the engine over by hand to make sure you haven't got valve/piston soup first, then do a compression test, although very unlikely you may be ok. Depends how hard you were pushing the car when the belt dropped off.

This post has been edited by dean on July 29, 2007 12:50 pm

[bigjohnh]

My condolences,

The engine is the same across the Peugeot/ Citroen range so the bits should be easily obtainable. When I got my belt changed a few months ago the mechanic charged me for a timing belt 'kit' which included the tensioner, perhaps that is what GSF list for the XM.

The head will probably be stuffed, my advice for what it's worth is to shop around for a second hand head and change it complete as the labour charges for overhauling the head and the cost of new valves will sadly be high. Unless of course you do it yourself in which case good luck.

John

[onthecut]

Hi Andrew.

Hard luck -- a real sickener. One other thing to do is to clean and check very carefully the piston crowns, if the valves have clobbered them. I had a tensioner bearing fail on an AX I had (a brand new piece, as well !) which did for the belt and valves. Did the valves etc. and thought no more about it. Put it back together and all was apparently fine. A few thousand miles later loud bang, immediate smoke screen and oil slick on the road. Examination showed the piston had partly disintegrated; con rod through the block, engine scrapped.
I can't be absolutely certain, but my money is on the fact that when the valves originally hit the piston, they maust have started a minute crack, leading to the catastrophic failure. So, anything similar in future, it will be a very close look indeed at the site of the impact on the piston.

Mike.

[medwaycitroen]

Every now and then an XM is lucky enough to come away unharmed. We had a cam belt snap abotu two months ago, we insisted to the owner that we were definite it would mean a new head, but after much persuading we put a new belt kit on (it's best to put a new tensioner on with every belt, really), and the car got away scott free. Every now and then it happens!

[Andmcit]

Well...

I fitted a new tensioner with it all set up and timed correctly and the engine will turn over
by hand with no obvious noises or resistance etc.

BUT

I didn't see the point of assembling anything further as the shim disc that sits beneath the
cams is visibly too low on two inlet valves compared with all the others. Looks like I'm
up now for a head off and replacement valves at least on the two that aren't looking right.
As a matter of fact I was just about to undo the main head bolts and lift the head now when
rain stopped play...

On this particular engine setup is there anything special about how this shim/disc under the
cam/at the end of the valve is removed? I expect to compress the valve but am not yet
prepped to deal with this new feature I've not seen before!

Andrew

[dean]

Hi Andrew

A Haynes manual will help you greatly here, 'a picture speaks a thousand words ' and all that.
But, remove the camshaft, and the disc you refer to is the follower, and is can shaped, a sucker on the top will pull it out or tilting the head, ( they float freely within the head. Be careful under the follower are shims keep each valve with its follower shims and spring etc and their aperture.
I could continue but you are best off with the manual as it has the torque ratings, valve clearances etc that you will need to re-assemble the head.
Sorry to hear about the dead valves anyway, hope you get it sorted soon.

PS the cam belt kit was £40, i modified the post but thought i would say in case you didn't notice

Regards Dean

[Andmcit]

Hi, thanks Dean.

I'm following Haynes, Russeck and the Revue Technique, but NONE actually say/show how
the follower [or shim/disc as I incorrectly called it earlier!! ] actually comes out.

I see now the can style of the follower and they float freely on a spare good head with the
camshaft removed although I want to use my original engine's head as it's mating HG face
is better so will swap the two bent valves I've now confirmed by removing the head this
morning. they're both inlet valves - all the rest seem to seat well.

They certainly dont look like they're going to 'fall out'...

Andrew

[Andmcit]

4 BENT INLET VALVES!! Certainly some impact marks on the outer crown of the piston.
At the moment I'm forced to take my chances with them...

And what's wrong with an actual final tightening torque figure rather than faffing about
with stretch bolts and angles!?

Andrew

[dean]

Hi Andrew

Sorry to hear you lost all 4 inlet valves .
Angle tightening is used because a 90o turn of the bolt will compress the head by a known amount. If you were to use torque only there is no guarantee that all head bolts will have tightened down evenly due to varying resistance of the threads if you see what i mean.
Good luck anyway hope your back on the road soon!

[onthecut]

Hi Dean.

I'm a bit bemused myself (not that it takes much doing) about this angular tightening game. To quote your example, but take it to a hypothetical extreme, let's say there is so much resistance in the thread that the bolt hasn't even touched the head at the appointed torque. In that case, another 90deg. may produce virtually no tightening of the head. Conversely, if it's on the head and accidentally or otherwise overtorqued and then 90 deg. is applied, you may lose all elasticity in the bolt.
It's certainly my impression that any angularly tightened bolt I've done has always seemed vastly tighter than I would ever set a similar size fastener from experience. For the sake of emphasising the need to make sure threads are clean and to always use new fasteners, I have a suspicion there's somehing lazy about this angle way of doing them.

Mike.

[dean]

Hi mike

I must admit you are right, whenever they are angle tightened they always seem far too tight, And i have to admit i always follow stage 1 and 2 torque settings with allows the head to clamp down evenly then instead of using the angle gauge i tighten them till it feels right. Now although i have never had a problem doing up head bolts and never have i had the head gasket blow after doing this it would be irresponsible for me to suggest not going through the angle gauge motions. If anyone thinks I'm wrong about this angle tightening thing, please let me know, cos if I'm chancing it a bit by avoiding using this method i will obviously need to amend my ways
Don't forget to put a bit of high temperature grease on those head bolts too!

[xmexclusive]

Hi All

I have been watching this with interest. I think that the angular method is essential when new bolts are used to get the initial "permanent set" extension in the high tensile steel bolts. For the steel of the bolt to yield and stretch fractionally when in use could cause problems. When it comes to reusing bolts they can just be torqued as the bolt steel already been stretched and extended. There are no instructions about tightening reused bolts as this is not recommended. It seems though that people have done this without problems.

Regards

XMexc

[dean]

MMMMMM.......... now where did i put that angle gauge

[DerekW]

I hesitate to argue with XMExclusive, but I would have thought that any stretch induced by the initial tightening of the head bolts would be well within the elastic limit of the bolt material. So no permanent "set" would take place.

Are the bolts tightened dry or lubricated? This is always specified on aircraft as it makes a huge difference to the tightness that is achieved.

Derek