Serpentine tensioner rubbing against timing belt cover

[alexqts]

Hooked up the new serpentine belt on my AAN today and found that the tensioner is rubbing against the timing belt cover quite badly making a huge noise (also evidence this has been going on for a long time due to a groove worn into the plastic cover). Checked the cover and it seems to be seated correctly. Even tried adding some washers in between the tensioner and mounting point, that fixes the issue but causes the belt to start jumping off the PAS pump!

Took the tensioner off and the main part almost looks distorted from a side profile - proper solid metal so not sure how it would have bent?? Maybe it's normal.

Has anyone had this issue before? I don't want to spend ££ on a new tensioner and cover on the off chance it could be something very simple!

[UrS4boy]

Serpentine Belt Info, importance, PNs and R&R procedure

Serpentine Belt Info, importance, PNs and R&R procedure

http://forums.quattroworld.com/s4s6/msgs/22579.phtml

[alexqts]

Cheers,

The part number of the tensioner is 054 903 133 A. It seems to be expensive / hard to find. I have however been able to find # 046 903 133 A.

Dimensions of the pulley are the same, everything looks exactly the same except it is listed for a C4 100 2.5tdi instead of the AAN.

I am guessing that the 046 is one model code and 054 is AAN S4 code? - so the part should be exactly the same I am hoping.

Anyone able to chine in regarding Audi P/N's and how they work?

Picture of the 046 903 133 A Gates part I have found:



Hopefully of good quality, not been able to find out where Gates manufacture the tensioners as of yet, but it seems to be the only UK option apart from going to the dealer.

[UrS4boy]

AAN Serpentine Belt Tensioner Pulley Options

I am not sure why you think you want/need a complete AAN serpentine belt tensioner. Typically the issue is the bearing on the pulley goes. This can be replaced or you can replace just the pulley with a very similar one from Volvo.

Read this (and note its hyperlinks to DIYs etc).

Further Investigations of the Volvo Serpentine Belt Tensioner Pulley and Tensioner Maintenance

http://forums.quattroworld.com/s4s6/msgs/308761.phtml

[alexqts]

I wish it was the bearing, then it should have been a fairly easy fix.

Unfortunately the actual metal housing appears to be bent inwards (area circled below) and not flush with the bolt holes. This is causing it to jam against timing belt cover.



I will check the tensioner again, but don't think it will be easy to fix.

[UrS4boy]

The part number of the (AAN) tensioner is 054 903 133 A. It seems to be expensive / hard to find. I have however been able to find # 046 903 133 A. Dimensions of the pulley are the same, everything looks exactly the same except it is listed for a C4 100 2.5tdi instead of the AAN. I am guessing that the 046 is one model code and 054 is AAN S4 code? - so the part should be exactly the same I am hoping.

*Wishing* is more like it. While there might be different PNs for the same parts used in VWs and Audis, I don't think that Audi would have the exact same part with two different prefixes, i.e. 054 and 046. No reason for that.

That said, here is the result of a little PN digging (you might (*MIGHT*) get lucky with the 046903133A afterall. MAYBE)

Okay, first of all for the C4 100 five cylinder engines including the AAT diesel, the AAR gas and AAN 20V turbo, there were three different serpentine belt tensioners:

AAT, AAS = 046903133A (shown below)
AAR = 054903133 (shown below)
AAN = 054903133A (not shown but we know this one)



Okay, so the serpentine belt tensioners mount on the same bracket that holds the Power Steering Pump and the Alternator. With a little poking, I was able to determine that the AAN bracket for this purpose is the 054145521C. Doing a cross check on this PN shows that it also the same bracket used on the AAT. This means that the 046903133A tensioner will bolt to the AAN bracket. That is the good news. The bad news (maybe) is while going through those parts diagrams, I found a reference to the bracket that stated "Use with 054903119D". Turns out 054903119D is a specific ribbed belt pulley for the alternator that is attached to that bracket. This might or might not be your issue, i.e. wrong alternator or wrong ribbed belt pulley on the alternator (sticking too far out or too far in). The 054903119D is the correct ribbed pulley for the 110 Amp AAN alternator.

[alexqts]

Thanks for looking.

I removed the tensioner today and it is definitely not straight all the way down. ~1-2mm difference pointing inwards from the top with the bolt holes to the bottom near the pulley. Hard because I don't know if it is meant to be slightly tapered inwards. Think the only way to tell is by getting a new part.

Might take my chance on the 046 903 133 A as I can get it for a very good price. If that doesn't work I will have to hold out for a good used 054!

[Monkeymagic]

Have you tried a good quality Motor factors for the complete part, say Andrew Page

[Zoig]

Even tried adding some washers in between the tensioner and mounting point, that fixes the issue but causes the belt to start jumping off the PAS pump!

Its pretty common that they bend inwards and start rubbing. I have used the shimming trick on my car with washers, ca 1mm washers on the top bolts and 1.5mm washer on the bottom, the main idea is to get the pulley running straight with the belt. It will be running a bit more towards the front edge of the belt, but it will work fine as a temporary solution.

You must have done something really wrong if the belt keeps jumping of the PAS pump.

[twoqu]

Its a guess but I suspect that the real difference in these tensioners is going to be the tension applied to the serp belt!
Tdi revs to say 5.5K, 10V 6.5K and the 20V to 7.5K. The casting for the AAN one clearly has the part number on which implies its a different casting unless any of the others also have it. So perhaps the AAN when is a beefer version taking into account the required tension. The wheel stays the same as I think they all use the 6PK belt.

[alexqts]

After taking the tensioner off last night and spending time comparing it to the photo's I have of the 046 903 133 A, it is quite different when you look closely. Although the bolts would match up it looks like the tensioner would not sit correctly at all. It may have been down to a variation in the aftermarket casting, but not prepared to take the risk.

Previously tried using a 1mm washer on the bottom bolt and that is what caused the belt to become mis-aligned with the PAS pump pulley, it must have been way too much.

So now on the lookout for some 10x16x0.3mm washer shims. Been all over but can't seem to find anyone that sells them. Guess I will have to wait for internet shipping! I'm sure I can even it out with the shims.

Just FYI for anyone who needs one in the future. Audi wanted ~£240 for the 054 903 133A part and it was also NLA . No auto factors had the part and no internet searches revealed anything other than the usual cheap Chinese stuff. I was able to find a few used ones on ebay.de so may have to get one shipped over if the shims don't work out!

[alexqts]

Its pretty common that they bend inwards and start rubbing. I have used the shimming trick on my car with washers, ca 1mm washers on the top bolts and 1.5mm washer on the bottom, the main idea is to get the pulley running straight with the belt. It will be running a bit more towards the front edge of the belt, but it will work fine as a temporary solution.

You must have done something really wrong if the belt keeps jumping of the PAS pump.

0.3mm shim was all it took! No more rubbing. On to the next problem!

[Zoig]

that is good to know. When i had the same problem on my car (the new tensioner was either way too expensive or NLA - can't remember what exactly) i just used washers i had hanging around in the garage. Worked really well for temporary solution.