s4wood

For those of you that haven't had a TBB tear...or for those of you who don't know you have a TBB tear..here are some of the symptoms I attribute to a typical TBB tear:

1)Power Loss - A TBB tear is usually accompanied by a noticable loss of power on hard acceleration. Most of the time..when you are just driving around on city streets...especially when it is cold outside (60 degrees or less)...the power loss is not that noticable...however when the car is heated up...so is the TBB...and if it is leaking boost...you will definitely feel the car feeling like it is being choked by the throat...with more throttle..you get no more acceleration...in fact, when you let off the throttle you get slightly more power..and a weird kinda thump noise. The RPM range that this seems most noticable is at about 3,500 - 6,000 rpm in 3rd gear.

2)Hissing sound during high boost - As the tear grows..you may get a hissing sound during the point when boost is supposed to be very high..like accelerating hard in 3rd gear from 55-80 mph. This sound will vary depending on where your tear is and the size of the tear...

3)Oil and Dirt residue under and around the TBB - Every time I have had a TBB tear..I have found a large amount of wet oily dirt under the TBB and in surrounding areas...near the F hose (for those of you with 2000 S4s...2001 S4s did not have F hoses any more). Just remove the plastic triangular cover...with a screw driver...and then reach under the TBB with you hand...if your fingers come back with grease and grime on them...you most likely have a TBB tear.

4) Abnormal VAG reading - although I am not sure of this...I believe you also get a strange reading from the VAG tool...maybe an overboost reading..probably right before the TBB tore. I don't have a VAG tool yet..so I cannot comment with any kind of certainty on this symptom.

You usually cannot visibly see any tears without totally removing the TBB..which takes about 30 minutes if you take your time and clean everything as it comes off. The tears are usually found UNDER the clamps..and cannot be seen unless the whole unit is removed from the car. Remember that when you change the TBB you will need a medium/small sized clamp for the boost sensor on the top of the TBB..it comes with a non-reusable clamp..and when you remove it...you need to get another clamp on there. Remember that you don't have much height to work with here..and a big wide clamp will NOT work. Also you might want to check the other vacuum hoses in that region to make sure they are secure...if need be..I would buy some 5/32" vacuum hose to have handy just in case you find out that one of your vacuum hoses is defective.

Anyway, I hope this helps people with this issue. This has been discussed many times before..especially when the S4 first came out back in Sept 99 and we were seeing the TBB tears more often. The fact remains...even though Audi has updated the part with the "T" version...it still may tear. Do not assume that because you have a 2001 car..with the "T" version...or because you changed out your "L" version in your 2000 S4...that you will now be safe from this TBB tear problem. It still happens...probably more likely than we like.

Signing off....

RocknRoll

Thks, i have noticed only once a boost loss under acceleration, but that was it!?

Deez

I think this would be made into an technical article on AW.

S4$$$pit

- 2000 Tip models don't have the F-hose either
- you can remove the TBB at just the two large clamps without taking off the nonreusable one for the boost sensor. If you do find a tear, you'll obviously then have to take off the third clamp to replace the TBB. If you don't find a tear, it could be under the third clamp, but I have had boost problems a couple times and the problem turned out to be elsewhere.

zeroS4

thanks Steve... now part of my bookmarks