Aux belt flapping and making a deep rumbling noise

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johnny625
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Aux belt flapping and making a deep rumbling noise

Post by johnny625 »

The aux belt on my Xsara 1.9 td (XUD9 turbo) is flapping badly between the crankshaft pulley and the ac compressor. The spring damper tensioner is jumping about and making a noticeable noise. This happens at idle and near idle. Above 1300 rpm or so the belt settles down and there is no noise. There is no play in the tensioners nor in the alternator or PS pump pulley. The pulleys seem to be inline and I don't think its a misalignment issue.

Despite the tensioners being changed about 10 000 kilometers ago I got me wallet out an bought new tensioner and the associated spring damper thingy. And guess what the belt still flaps about. I even tried it with a brand new belt and brand new crankshaft pulley. Still the same. However the aux belt is 1740 mm long. This according to the sellers is the right length for an XUD with A/C and power steering. Is this right? Might 1740 mm belt be simply too long to be tensioned properly?

I tried to tension the belt several times with the eccentric tensioner however even at max tension the belt still flaps about. I can twist the belt to 90 degrees and slightly beyond between the crankshaft and the AC compressor even at max tension and I don't claim to be a strong person. :) I do want to try things out with a shorter belt. Maybe 1730 or 1735 milimeters.


Can someone tell me a belt length that works good with this XUD set up?



One mechanic I talked to says its because uneven compression in the engine cylinders which makes the torque on the crankshaft pulley to come in uneven pulses thus making the belt flap. He says the only remedy for this is to install a clutch type pulley on the alternator which will not allow for the momentum of the alternator to be transferred on the pulsing torque that is delivered on the belt. This doesn't makes sense to me. The car was fine until recently and the pulley on the alternator is an ordinary one and not a clutch one. Also the engine runs smoothly not wobbling about which would suggest uneven compression with the belt off.
elma
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Re: Aux belt flapping and making a deep rumbling noise

Post by elma »

Not sure whats up but 1740mm is what gates have listed for a 1.9td Xsara with ac
johnny625
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Re: Aux belt flapping and making a deep rumbling noise

Post by johnny625 »

I know. Even with the eccentric tensioner at full adjustment the setting hole in the automatic tensioner does not line up. If I a manually put some pressure on the belt the holes do line up so I guess I need a new belt which is shorter.
elma
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Re: Aux belt flapping and making a deep rumbling noise

Post by elma »

Surely if you have the right belt then the problem is something else.
A shorter belt may help but if it was my car I'd want to know why the correct belt wouldn't tension up correctly
Xuds can take out the cambelt if the alternator belt snaps so it's not a good place to try new things
Just crossed my mind, have you measured the belt? Unlikely I know but it could be too long.
johnny625
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Re: Aux belt flapping and making a deep rumbling noise

Post by johnny625 »

I haven't measured it. Though on the new one it said 1740 on it. I just don't know what to make out. There is one possibility that I am beginning to think about. I have been told that different types of AC compressors have slightly different pulley diameters. Maybe the compressor was changed sometimes in the past and the pulley is smaller than the one on the factory fitted one.

Also how much movement in the auto tensioner is normal to begin with when the car is running if at all? I am just afraid that the new tensioner and the damper spring will soon get busted because of the vibrations.

Also I have noticed that when I turn the AC on and the AC compressor clutch engages the flapping of the belt goes away nearly completely though the auto tensioner is still bouncing somewhat.
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Re: Aux belt flapping and making a deep rumbling noise

Post by CitroJim »

Check your tensioners again; they can have a very short life and as James says, their failure can have very catastrophic results...
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johnny625
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Re: Aux belt flapping and making a deep rumbling noise

Post by johnny625 »

I have just checked the tensioners and they are both fine. No play in any of them.

Btw, what is the approximately right tension on the aux belt? Is twisting to 90 degrees a valid check in any way? The belt doesn't squeak at all which would suggest that is loose and not tensioned enough. Yet I can't make for the holes to line on the auto tensioner. At least not by solely using the eccentric roller. Also still flaps about like crazy. It is as if the auto tensioner get in resonance at low rpm's and makes this rumble while making the belt flap about. This morning I took it for a test drive and just sounds so wrong. The rumble can be heard inside at low rpm rather well. :cry:
Last edited by johnny625 on 30 Jul 2017, 10:22, edited 1 time in total.
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Re: Aux belt flapping and making a deep rumbling noise

Post by CitroJim »

No, a twist is not a valid test... It is not tight enough...

The tension is set by moving the eccentric tensioner until the 'pinning' holes in the spring tensioner aligns and a pin can be inserted..

This means the belt is tight enough to put the correct amount of pre-load into the spring tensioner... This is critical.

If this state of affairs cannot be achieved with the eccentric tensioner set at maximum eccentricity then the belt is too long... It may have stretched.

Swap it for a shorter one until the correct tension is achieved.
Jim

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johnny625
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Re: Aux belt flapping and making a deep rumbling noise

Post by johnny625 »

I will buy a shorter belt tomorrow and certainly try to tension it until the holes line up. Will let you know how things turn out.

Thanks for your advice.
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Re: Aux belt flapping and making a deep rumbling noise

Post by furriegurrie »

Are you sure you've routed the belt correctly? There are sometimes several ways possible....
johnny625
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Re: Aux belt flapping and making a deep rumbling noise

Post by johnny625 »

Absolutely sure in correct routing. Have checked it several times. Also all of the auxiliaries work fine but the belt is flapping and the auto tensioner bounces around making noise.

Seems to be an issue with belt tension as I can't put enough tension on the belt with the eccentric tensioner for the holes to line up on the auto tensioner. My guess is that I simply need a shorter belt. The AC compressor pulley seems a bit smaller than normal which might be due to the compressor being changed in the past.

Funnily enough the numbers on the old belt are rubbed off so I can't read what was it original length. I will measure it however.
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Re: Aux belt flapping and making a deep rumbling noise

Post by KennyW »

I thought there were 2 different sizes 1735mm and 1752mm for the 2 different ac compressors.

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johnny625
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Re: Aux belt flapping and making a deep rumbling noise

Post by johnny625 »

I must have the AC compressor with the shorter belt then in my car. It seems possible that a 1740 mm belt with that much jumping around has gotten stretched to a point of being too long.

Thanks.
elma
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Re: Aux belt flapping and making a deep rumbling noise

Post by elma »

Stick up your vin and one of us can check what service citroen has listed.
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Re: Aux belt flapping and making a deep rumbling noise

Post by KennyW »

The shorter belt is for the sanders AC compressor and the longer belt is Delphi compressor.

Kenny
C5 x7 2.0 HDi 160 hp Estate exclusive, the newbie
Xantia 2.0 Hdi 90hp 1999 only 189,000 and rising!!!!!!! Moved on to a new home
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