Ad496

12v 2.8, Bentley lists the timing belt tensioner at 45Nm, can anyone confirm that this is not an error in the book.

It seems awfully tight for a M8 (6mm hex bolt), I've taken it to about 40Nm, and it has the bad 'Gonna strip any second now' feeling about it.

The idle roller, is a much larger diameter bolt, and only is spec'd at 25Nm!

A6Gary

<ul><li><a href="https://forums.audiworld.com/a6100/msgs/66617.phtml">Tightening Torques</a></li></ul>

nothing

Just replaced the one on my B4 yesterday, no problems cranking it down that tight.

Ad496

Thanks, as something just didn't feel right I backed the bolt out and check it. On careful inspection I noted a fracture right through the bolt, it was ready to sheer at any moment. Off to the dealer for a new bolt!

A6Gary

Great catch. It pays to know the "feel" of working on any vehicle.

Audi Lemens

Even though this is an old post, I feel that a reply may be necessary. I too felt that the torque specs for the tensioner and idler pulleys may be incorrect in the Bentley manual. Bentley manual has reversed the torques for newer A4s so that the larger bolt gets 33 Ft. Lbs. and the smaller M8 bolt gets 16 Ft. Lbs.. To be sure, I looked up the max torque recommended for a grade 8.8 M8 bolt and it turns out to be 18 Ft. Lbs. This information would explain why I've seen many failures of this M8 bolt shortly after timing belt replacements. The M8 bolt may seem to accept the 33 Ft. Lbs. of torque, only to fail shortly thereafter.

ky90025

I had the same issue. Tried to torque the tensioner M8 bolt to 33 ft-lbf and the bolt sheared. I was confused and got a new bolt and torque it to a point of about 25 ft-lbf, started to feel the bolt yield and stopped. I was using blue locktite which reduces friction and will put a slightly higher tension on the bolt. Looks like what "Audi_Lemens" said is correct Bentley made a mistake on the torque spec, unfortunately probably on one of the most important torque specs in the manual!

Like Audi Lemens stated never go higher than the maximum torque specification for a given grade of bolt. If the manual states higher its probably an error.

M6 grade 8.8 is 7 ft-lbf or grade 10.9 is 10 ft-lbf
M8 grade 8.8 is 17 ft-lbf or grade 10.9 is 25 ft-lbf
M10 grade 8.8 is 35 ft-lbf or grade 10.9 is 49 ft-lbf
M12 grade 8.8 is 60 ft-lbf or grade 10.9 is 85 ft-lbf

The chart below is from a bmw bentley manual. The torque values are in N-m. Multiply the N-m values by 0.74 to get ft-lb.

There are a lot of torque error in the bentley manual, sometimes they switch N-m and ft-lbs too. In general the bentley manual is not that good for the B5 A4, it tries to cover 3 different engines and does a poor job.

haraldpost

****...I did the camshaft sprocket seals on mine yesterday. We thought 45 nm was high on that tensioner fastener M8 bolt, but followed spec. I will head to the dealer now to get a new 10.9 bolt and tighten it to 33 nm!

Audi Lemens

33 nm is still too tight for the small hex head bolt that holds the tensioner roller. The correct torque is 16 ft. lbs. With a maximum torque of 18 ft. lbs. The original Bentley manual had these torques reversed with the larger idler bearing bolt which should be 33 ft. lbs. which I believe is around 45 nm.