B8/8.5 S4 unique problems and symptoms megathread

[Morritse]

I think it would be a good idea to address the common problems that are rather obscure and unique to our cars.

The motivation behind this thread is seeing repeated posts about the same issues over and over.
The goal is to provide an index of the most common problems, how to effectively diagnose and differentiate between them, and offer advice on how to remedy them

For now, I want to generate a list of the problems we have, and later I can elaborate on their symptoms and solutions. Please help me add to the list!

Things that are somewhat ubiquitous among all engine I don't want to include (spark plugs etc.)

FORMAT:
will be grouped by symptoms, causes will be listed below. Since causes will be repeated, causes will be listed below the list along with in depth descriptions, further diagnostics, and solutions.


Common Symptoms


clunking especially at low speeds and over bumps
Torn control arm bushings

misfires and decreased performance
Catalytic converter failure
Supercharger IC failure/leak

coolant loss
Supercharger IC failure/leak
PCV failure
Thermostat failure
Water pump failure
Crossover pipe leak
Coolant reservoir cap failure

Overheating issues
Thermostat failure
Water pump failure

B8.5 Electric Steering issues: Notchy and vague steering input/output, wandering on road
Faulty steering rack
Faulty intermediate shaft
Electronic issues


Diagnosing and repairing common problems


PCV failure

• coolant loss at an increasing rate, usually invisible and undetectable by pressure test
• coolant in oil
• excessive steam in exhaust
• milkshake under oil cap
• Suction through oil fill cap
• rough start especially after car rests for short periods after driving

PCV failure Resource https://docs.google.com/document/d/1...t?usp=drivesdk


IC failure

• coolant loss
• misfires in cylinder 3 and/or 6
• rough starts
• fouling of spark plug 3/6

IC failure resource https://docs.google.com/document/d/1...it?usp=sharing


Catalytic converter failure

• Change in exhaust tone (usually muffled and deepened)
• misfires in cylinders of one bank (corresponding to the side of failed CAT) especially under high loads
• white residue around exhaust exists
• loss in power
• possible catalytic converter codes

Catalytic converter resource: https://docs.google.com/document/d/1...t?usp=drivesdk


Thermostat failure

• engine overheating
• fans running when engine off or running excessively hard all the time

Water pump failure
Control arm bushings failure
Wheel bearing failure
Crank pulley failure

[Brother Owl]

B8.5 Electric Steering issues: Notchy and vague steering input/output, wandering on road
Fixes: Replace/recalibrate faulty steering rack, replace failed intermediate shaft, disable DSR with VAGCOM

[Morritse]

B8.5 Electric Steering issues: Notchy and vague steering input/output, wandering on road
Fixes: Replace/recalibrate faulty steering rack, replace failed intermediate shaft, disable DSR with VAGCOM

I'll add stuff like this as it's posted!

[Snowmonkey]

Will this include the rattling at cold start sort of problems?

[Morritse]

Will this include the rattling at cold start sort of problems?

Yes. The timing chain guide thing should be here. If you want to add some info feel free to and I'll add it to post

[Snowmonkey]

Yes. The timing chain guide thing should be here. If you want to add some info feel free to and I'll add it to post

Ill let someone more familiar with the problem, as Im still trying to figure it out myself

[Johnson]

Subscribed. I like threads like this. Specifically interested in cat diagnosis and fixes. I've got a feeling I'll be going down that road soon...

Sent from my SM-G920V using Tapatalk

[Morritse]

Subscribed. I like threads like this. Specifically interested in cat diagnosis and fixes. I've got a feeling I'll be going down that road soon...

Sent from my SM-G920V using Tapatalk

I added a cat resource Google docs.

Everything is living, and will be added to as I have time and get more info :)

[03redgti]

doing my thermostat this weekend ..should be fun

[wangshuo1989]

B8.5 Electric Steering issues: Notchy and vague steering input/output, wandering on road
Fixes: Replace/recalibrate faulty steering rack, replace failed intermediate shaft, disable DSR with VAGCOM

are you sure replacing the rack will fix it? I would love to have this fixed. But since the rack costs $1700 I want to know for sure before I do it.

[Brother Owl]

are you sure replacing the rack will fix it? I would love to have this fixed. But since the rack costs $1700 I want to know for sure before I do it.

In my case they replaced the failed intermediate shaft - probably a cheaper fix. You might want to start there. I have heard of other owners replacing the entire rack but that may have been due to other issues (e.g. worn/broken teeth in the steering gear)
But man I am EXTREMELY pleased it's finally fixed!

[Morritse]

In my case they replaced the failed intermediate shaft - probably a cheaper fix. You might want to start there. I have heard of other owners replacing the entire rack but that may have been due to other issues (e.g. worn/broken teeth in the steering gear)
But man I am EXTREMELY pleased it's finally fixed!

I'm not familiar with the b8.5 specific problems, for obvious reasons :p

Does someone here want to create a list in a similar fashion for the steering problems as well as a similar Google doc so I can add it to the list?

[wangshuo1989]

In my case they replaced the failed intermediate shaft - probably a cheaper fix. You might want to start there. I have heard of other owners replacing the entire rack but that may have been due to other issues (e.g. worn/broken teeth in the steering gear)
But man I am EXTREMELY pleased it's finally fixed!

Thanks for the info, I'll contact my local shop to have them look at then

[ip428]

man... thanks for the info on this. Have had a rattling cat at start up. and a semi misfire feel for a couple of days now, but no misfire codes other than the p0420. I will be replacing cat to see if that brings the idle back to normal!

[BT719]

Wow, what a great guide with great potential to grow as we determine more quirks. Any chance for a sticky?