Serpentine belt peeling off

[MikeT]

Those of you that read about my crank pulley issues following a cambelt change may not be surprised (do I hear "Told you so"? ) to learn my serpentine belt has failed. A thin outer length has been stripped away - a bit like one of those cheese straws - though the majority of the belt is still in place and got me to a local parts shop (new belt purchased) and then home, thankfully.

Despondent and with other work to do I haven't examined the area yet but don't know what to do whatever I find.

I'd really like to understand the reason it failed, considering the wear problems with the crank tail keyway and subsequent damper destruction.

I'm thinking there may be an alignment problem? For instance, can the crank pulley be too far back or forward - does crank end-float wear cause this?

What would you do with this car in this condition?

[MikeT]

UPDATE: On inspection I think I've found the reason for the failure. The belt is grooved (five I think) and a strip has come off the outer side of the belt so I now have a modified four groove belt.

Now, here's the odd thing. On all pulleys except the A/C the vacant groove on each wheel is nearest the engine. But on the A/C pulley, the vacant groove is the other side. It appears the A/C compressor is not aligned and too far out (towards the wing).

I'm really baffled as to how, and more importantly when, did this A/C compressor move out of alignment? It can't, AFAICT which means I've been driving it like this for thousands of miles without the belt complaining until I recently reset it's tension.

I'm really tempted to just leave it like this as it still runs (even better now I assume) and doesn't squeal anymore.

[CitroJim]

Mike,

I've had two cases of this. One was on my Activa where the belt was running a groove out on the HP Pump. That one was caused by the wrong alternator being fitted which caused its pulley to run a little too far out and pulled the belt to one side.

The other more relevant case was on a 1.9TD that shredded its belt on one side and that was caused by the spring-loaded tensioner running out of line because either its bearing had failed or because its shaft was bent. It was easy to spot when you looked as it appeared to be cocked up at an angle.

Take the belt off and "eye" all the pulleys and tensioner jockeys to see if they're all running nicely square and true. Any deviation from true alignment that will pull the belt to one side will not be difficult to see.

It is very unlikely the aircon compressor is out of line as there is no adjustment on it. The only aircon compressor related issue that could cause this is a duff bearing on the aircon compressor clutch but you'd know about that from an entirely different set of symptoms. Whist the belt is off though, it would be worth checking for play in the aircon compressor pump clutch/pulley assembly.

I am wondering if your "new" crank pulley may have a different offset. Did it come off a similar vintage Xantia? Early non-aircon ones from, say a 405, may have a diffrent offset. I seem to recall my 405s did not have quite the same pulley on them as later Xantias.

[MikeT]

With the engine running the belt looks absolutely fine alignment wise. I assume the belt has simply modified itself. The difference appears to be the A/C pulley being two grooves forward (away from the engine) compared to all the other pulleys and tensioners.

Yes, the crank pulley did come off a Pug (306 I think) and I have no idea what the set up was for that car, most parts were missing.

The thing is, though it may be the placebo effect, the car seems to drive smoother, quieter (not surprisingly!) and more responsive in pick up.

I will double check to see what is out alignment but I'm confident it is the compressor.

[MikeT]

Ok, I looked, I used a steel rule, I used a laser leveller but can I determine if anything is out of alignment? No.

I did try the A/C compressor pulley for play but it was miniscule, barely a half mm. What I did do was reset the remaining belt equally on all pullies and ran the engine to see if it would complain, which it didn't. It still drives fine.

So, I can only draw one conclusion on this. User Error.

[xantia_v6]

can I determine if anything is out of alignment? No.

So, I can only draw one conclusion on this. User Error.

Simply fixed, you need a new user

I was thinking anyway, that if you have got a servicable but narrow belt, then you don't lose much by putting it on and see what happens. It might run perfectly, or it might shed another O-ring, either would tell you something.

[1900sr]

I had this after changing my air-con pump. In my case I'm pretty certain I damaged the belt when refitting it (brute force and ignorance not always being the best way!)

I was thinking anyway, that if you have got a servicable but narrow belt, then you don't lose much by putting it on and see what happens. It might run perfectly, or it might shed another O-ring, either would tell you something.

I thought that, but stopped thinking that when the belt shredded another strip which caught up on the cambelt and caused it to jump two teeth on the fuel pump pulley. Just thankful it wasn't on the cam pulley!

[MikeT]

After the remaining belt began chirping again yesterday I took a brief look and discovered that the crankshaft pulley appears to be sitting too far towards the engine compared to the A/C compressor pulley, therefore the first ridge of the belt is actually riding on the peak of the outer pulley groove instead of in the valley. I suspect the rest of the belt isn't seating properly either and this would explain how one o-ring of the belt got shredded off so precisely.

I can only surmise that the crank keyway wear is allowing the pulley to sit too close to the engine, thus being out of kilter with the rest of the pulley's. I think I can adjust the belt position to accomodate this. Not ideal but it should work.

[CitroJim]

I can only surmise that the crank keyway wear is allowing the pulley to sit too close to the engine, thus being out of kilter with the rest of the pulley's.

No. The crank pulley inner boss is pulled tight up against the cambelt sprocket which is in turn pulled up tight against the oil pump drive sprocket boss which in turn is pulled up tight against a step in the crankshaft tail. All is held very tightly together by the clamping action of the crank pulley centre bolt. The keyway being worn can have no effect on lateral position. the only thing that can have an effect is the crank pulley inner boss offset being incorrect which I mentioned in an earlier post.

A piece of trivia. Very early XU engines did not have a keyway and woodruff key on the oil pump sprocket and thus relied on the friction created by having the crank bolt very tight to drive the oil pump. If the crank bolt came loose you lost all oil pressure! Later XU engines have a key simply to guard against this eventuality.

I think I can adjust the belt position to accomodate this. Not ideal but it should work.

How? Nothing has any lateral adjustment ability Mike. The only sure answer is to replace the crank pulley for one with the correct offset.

EDIT: It is possible all this could be caused by excessive crankshaft endfloat although this is very rare on an XUD. Worth checking though. Push and pull on the crankshaft and feel for lateral play.

[CitroJim]

Mike,

A better way to check if you have excess crankshaft endfloat is to have an assistant operate the clutch whilst you observe the crank pulley. Endfloat will then become easy to see.

[poggle]

hi i'm new on here but i've got a 2.1 and the belt started shreading on that, eventually i ended with a belt like a boot lace just got to work and called AA man he would not put new belt on, bearing on spring loaded tensioner pulley worn if you looked down the alignment it was leaning slightly forcing belt to shread on other pulleys new one from cit £104 don't think it will last it just keeps shreading

[falling-out-with-my-car]

Hold onto your seats ppl I had this problem last december, I was driving uphill when I heard a clicking from under the bonnet, the serpentine/auxillary belt had the inside edge stripped away and it had wrapped this stripped length around the back of the hydraulic pump pulley.

I managed to creep home and rplaced the belt the next day it was a tenner, it lasted exactly a month and the next time it went in the same place on the same road this time the belt completely shredded and came off the pulleys I did wonder if i had bought a crappy belt but once I opened the bonet I could see that the centre pulley was leanning towards the engine on one side, which was dragging the belt towards the corner of the engne block and tearing it apart.
I found a local mechanic who said he would replace the pulley all in for a 100 quid but my car sat outside the garage for over a week he didnt touch it once, soone week before christmas i called auto home and had it taken to citroen, it cost me 400 quid for 3 new pulleys and a new belt, its lovely now and Im glad its over but citroen were a bit expensive , mind you when you ask to see the schematic drawing of the top pulley behind the fuel pump and realise that it actually sits half inside the engine block you will wonder how the hell it fits together it looks like a nighmare to fit. so if your belt keeps shreadding itself your pulleys are telling you its time for repalcement some auto factors sell the pulleys seperately and some only sell them as a kit so if your attempting to fix it on your own check out a couple of outlets first I hear its a pig of a job to do but so is everything on an xantia. the pulleys are not cheap either at around 50 quid each.

Regards Nigel.

[davek-uk]

As Jim says it is worth checking the offset of the crank pulleys. However, in most cases it'll be a worn pulley, tensioner or roller running out of alignment. When the spindles or bearings go they'll be pulled inward at their outer edge by the tension of the belt. This has the effect of trying to realign the running of the belt as the belt tries to run up the damaged pulley wheel. I haven't had this problem with aux belts but a failing water pump spindle tried to run my cambelt off!

Dave

[falling-out-with-my-car]

dave

it was citroen that called it a auxillary drive belt probably because they are all a bit thick.

Nigel.

[MikeT]

Well whatever the problem was, it's not mine anymore