Timing Belt Failure (Update)

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Richard Gallagher
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Timing Belt Failure (Update)

Post by Richard Gallagher » 29 Jan 2005, 03:42

I've now taken a look at my latest project of the 2.0 16V Xantia with the broken timing belt.
I found that the belt has snapped, but looking carefully at the belt I noticed that there are several other points where it was also about to break, all of them on the outer edge.
The outer edge has also worn at an angle (no longer 90 degree edge) and that there is wear on the cam cover where the belt has been rubbing against it.
What are these the symptoms of?
Was the belt over/under tensioned from new, or was it a duff belt or just run over on time (over 5 years?)
I have seen pictures depicting cause/symptom but just when I need them most I cannot find them.......typical[:(]

alan s
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Timing Belt Failure (Update)

Post by alan s » 29 Jan 2005, 04:25

Richard,
When I did the cambelt on my 2.01 8 valve, I found that there was a rim inside the actual tensioner that it was possible for the internal sleeve to ride up on. There was also a burr in the moulding that allowed it to sit on a very slight angle. The result was the tensioner sat slightly cockeyed which tended to send the belt towards the front of the engine and on to the cover. It was possibly to get the tension correct by overtensioning and thereby having correct deflection at one side of the belt but a much tighter one at the other. I knew as soon as it started to run off something was wrong and kept paddling around until I found it.
Once the tensioner sleeve was fitted correctly, it has been right ever since.
I'd suggset that as being the place to start. Being a 16V it would have 2 tensioners I'd imagine, in which case there's a possibility that one is sending it off true whgilst the other is trying to correct it and this could also be adding to the overtensioning.
Alan S

Richard Gallagher
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Timing Belt Failure (Update)

Post by Richard Gallagher » 29 Jan 2005, 04:42

Interesting one that Alan, I'll take a look and report back.
Thanks for the suggestion.

oilyspanner
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Timing Belt Failure (Update)

Post by oilyspanner » 29 Jan 2005, 05:31

Yheres nothting to restrain them on the outside edge, is something getting near it?
Stewart

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AndersDK
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Timing Belt Failure (Update)

Post by AndersDK » 29 Jan 2005, 15:04

I've seen this on a BX 1.6 engine.
The cause was a worn water pump bearing causing the pump axle to tilt, and then the belt starts running in an angle, effectively trying to run off the beltwheels - chafing against the cover.
In this instance I found the problem when the belt had approx half the width left. The engine had a strange squeeking sound while running.
Talk about high time ...

alan s
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Timing Belt Failure (Update)

Post by alan s » 29 Jan 2005, 15:50

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by AndersDK</i>

I've seen this on a BX 1.6 engine.
The cause was a worn water pump bearing causing the pump axle to tilt, and then the belt starts running in an angle, effectively trying to run off the beltwheels - chafing against the cover.
In this instance I found the problem when the belt had approx half the width left. The engine had a strange squeeking sound while running.
Talk about high time ...
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Yep, I agree, anything that's not sitting true will allow the belt to both throw to the outside and also wear along that edge. As I said earlier, this basically allows the tension to be tighter at one side of the belt to the other.
Another point often missed on setting manually adustable tensioners is that the direction of rotation is often a critical factor. I have had owners tell me that they have fitted cambelts but couldn't get the tension "right" no matter how hard they pulled back on whatever tool they were using to set it. This is usually caused by the tension being set by rotating the tensioner in the wrong direction which causes the tensioner to apply pressure at a point different to that specified by the manufacturer. This often results in the person setting the tension to overtighten, notice the belt still doesn't feel correct, yet causes it to whirr as only an overtightened cambelt will, followed by the logic that "it'll bed in" which in this case doesn't happen. All ythis does is fractures the webbing and causes premature failure.
FYI, on a BX 16V it is recommended to adjust in an anti-clockwise direction. I am not 100% sure on a Xantia 16V but I think I have also read something to this effect also. I think I have also been told that the Xantia 16V had a modification to the tensioner too, but it will take someone more au fait with Xantias than me to confirm this.
Alan S

ACTIVE8
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Timing Belt Failure (Update)

Post by ACTIVE8 » 29 Jan 2005, 17:36

<u> Regarding timing belts, and their possible failure. </u>
I remember with Ford's pinto engine, something about the fact that if you had a 2.0 litre engine, and had the timing belt fail, that you would have a less expensive problem, than the owner of a car with the 1.6 litre engine.
This was because the 2.0 litre engine had a physically slighter taller cylinder head. This difference was noticable from the front where you could look at the clearance above the water pump pulley, and see about an extra inch of height.
So apparently if the timing belt failed then there would be no contact between the valves, and the pistons. While with the 1.6 litre engine having less clearance, there would be the possibility of contact, with bent valves, damaged pistons etc being the expensive result of this.
The pinto engine is an eight valve engine. I think that when you have a multi valve engine, it actually increases the possibility of contact.
How do Citroen models past, and current cope with this unfortunate incident ?
Do they contact, or do some models have clearance ?

Richard Gallagher
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Timing Belt Failure (Update)

Post by Richard Gallagher » 30 Jan 2005, 00:14

Well I removed the head this afternoon and found that the exhaust valves on cylinder no 1 had collided and been bent as a result. There is also evidence (due to carbon disturbance) that the inlet valves on no 1 + 2 cylinders have collided, albeit very gently.
What I do find interesting is that there is significant wear on the crankshaft pulley caused by the belt rubbing up against it.
The water pump has a slight leak which has been going for some time looking at the deposits but it turns relatively freely, no harsh areas in the bearing and no noticeable slack in the bearing.
However the fact that it has been leaking would appear to support Anders and Alans theory of it running out of alignment.
Both of the other tensioner pulleys appear to run OK.
Now the question, what are the chances of the conrod on no 1 cylinder being bent and are the piston rings liable to be damaged?
Do I now replace the water pump, both tensioner pulleys and crankshaft pulley and then fit the head from my other car, or do I swop engines?

PowerLee
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Timing Belt Failure (Update)

Post by PowerLee » 30 Jan 2005, 00:29

The conrod is unlikely to be bent.
The cambelt snapped on my 2 litre 16 valve 406 years ago, That bent 11 valves! ( Thanks Peugeot lack of recall! )
Turn it over & see if the engines moving freely & check the piston height between the 4 cylinders.

alan s
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Timing Belt Failure (Update)

Post by alan s » 30 Jan 2005, 03:00

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by ACTIVE8</i>

<u> Regarding timing belts, and their possible failure. </u>
I remember with Ford's pinto engine, something about the fact that if you had a 2.0 litre engine, and had the timing belt fail, that you would have a less expensive problem, than the owner of a car with the 1.6 litre engine.
This was because the 2.0 litre engine had a physically slighter taller cylinder head. This difference was noticable from the front where you could look at the clearance above the water pump pulley, and see about an extra inch of height.
So apparently if the timing belt failed then there would be no contact between the valves, and the pistons. While with the 1.6 litre engine having less clearance, there would be the possibility of contact, with bent valves, damaged pistons etc being the expensive result of this.
The pinto engine is an eight valve engine. I think that when you have a multi valve engine, it actually increases the possibility of contact.
How do Citroen models past, and current cope with this unfortunate incident ?
Do they contact, or do some models have clearance ?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
There are what is known as "Interference" and "Non Interference" engines in these more supposedly 'developed' engines that rely on a strip of rubber for their survival.[:0][:0]
The Intereference being like most Cit/Pug engines where in the case of say the BX16V there are sections cut out of the piston face to allow for the valves when seated to avoid colliding with an upcoming piston, and the Non Interference whereby the pistons would still spin merrily whilst the valve dangled around up in the combustion chambers out of harms way. Whilst the interference type engine is a cause for concern, it seems these days the trade off is increased performance against the inevitable destruction of an engine top end if the belt snaps. It would appear that in the design however, that it is more the exception than the rule that the bottom end of the engine suffers too severely as it seems to be engineered into them for things to let go at the top to allow the major part of the engine to survive. In the instance of the diesels, the camshaft often snaps in 3 places whilst on the petrols, the valve seem to bend before anything major lets go down below.
It is usually the case that the belts actually snap on gear changes, at idle or on take off; when the tension is momentarily released for any reason.
On that basis, I'd suggest that Richard will get by with a top end repair, pump and possibly tensioners but firstly, find the cause to prevent a rerun of the belt damage.
Alan S

Richard Gallagher
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Timing Belt Failure (Update)

Post by Richard Gallagher » 30 Jan 2005, 03:31

Thanks Alan, as you suggest, this belt apparently broke whilst the car was idling at traffic lights.
The section of belt which broke was actually between the two camshafts, although as I mentioned above the belt has several areas where it has started to break up, all of them on the outside edge which is worn at an angle from the teeth side.
I'm tempted to believe that the water pump is to blame but to be honest I cannot see, when looking from above, any signs of it being out of alignment.
What is clear is that the belt has been trying desperately to run off its pulleys, only being prevented from doing so by the crankshaft pulley which has worn considerably, particularly considering that its a rubber belt that caused the damage.
If I can work out how to post pictures I'll put some on here.
Interestingly I also took a look at the 'donor' cars belt today, 120k miles, no record of it ever being changed and its in good condition apart from being VERY loose.

alan s
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Timing Belt Failure (Update)

Post by alan s » 30 Jan 2005, 03:47

Richard,
When you fit the new belt, (remove the locating pins) take the LT plug off the coil and give the engine a spin by turning the key with your arm through the drivers window so you can clearly see the cambelt. If it is still out of whack, it will run almost immediately towards the outside. Mine was about 3 to 4 mm from the edge when it was running true.
It sounde as though the water pump is on the way out but in my opinion, it would need to be pretty badly worn to be on such an angle as to send the belt off the scale.
How were the tensioners? Tight, noisy or sloppy?
Have you checked to see if either were internally riding on that inside edge. This is often detected by looking at the underside of the tensioner, the part that is affixed to the block and in my case, a clear mark was visible showing it wasn't sitting flush. It's just a theory, but did you get any idea looking at the positions of the eccentrics, which direction the tensioners had been adjusted in? The position of the break suggests to me that it just may be a contributing cause, allowing a bit of flap between the cam sprockets.
Alan S

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Panjandrum
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Timing Belt Failure (Update)

Post by Panjandrum » 30 Jan 2005, 03:52

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by PowerLee</i>

The cambelt snapped on my 2 litre 16 valve 406 years ago, That bent 11 valves!<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Shocked and amazed!! How did it feel driving a 2 litre 16v way back in 1598? And how has it been running in the four centuries since?

Richard Gallagher
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Timing Belt Failure (Update)

Post by Richard Gallagher » 30 Jan 2005, 04:23

I've spun the tensioners, they are quiet and run with the usual minor 'resistance'. There are no obvious signs of wear on their running surface.
I'll get underneath tomorrow and take a look at the mounting/running of each one, but I believe they are each mounted on a post.
The cam cover does have wear/rubbing marks on it half way up the belt run, but then thats not surprising considering how the belt was running.

The belt would appear to be the original factory fitted item, I have the full service history for the car from new (Owned by Citroen UK for the first 10K miles) with all receipts from a Citroen main dealer, the last owner never had the belt replaced after having bought the car at 48K miles 4 years ago.

alan s
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Timing Belt Failure (Update)

Post by alan s » 30 Jan 2005, 04:46

Richard,
If they are the same as those on a 16V, they are held on by a single allen headed bolt. It takes a 6mm key but whatever you do, don't try to remove it by using an Allen key as such; use a key that fits a 1/2 drive socket set otherwise it will round off internally.
The will be no signs of wear on the outer surface only a mark where the belt gas run. On a 16V, it is handy to have access to an engine crane (a jack will work at a pinch) to raise and lower the motor to get access to the tensioner mounting bolts usually through the inner guard section after the road wheel is removed.
Once taken out, you'll be able to inspect the backs of them to determine if they have been incorrectly fitted or even if one may have worked a bit loose.
Alan S