Clutch vibration, not stable rpms, hissing noise, belt noise(?)

Hey Guys! It's one of my first posts up here since I become an owner of an Audi 8P1 from 2005 (It's my first car ever). Typically, as it's my first car purchase ever I needed to **** up a bit and miss out on noticing few issues with it, so if you would be nice enough to give me a little hand with it that'd be great. I'm keen to learn and start from simpler fixes at home, but I'm by no means a skilled DIY-er or have any previous experience with cars, so please if you can use a simple language, it would help me greatly! Here are the issues:

1. CLUTCH VIBRATION - in line with RPMs, it doesn't slip, make any noises. But lightly resting your leg on pedal makes you uncomfortable after 2000 rpms. I tried looking it up but usually clutch vibrations are associated with acceleration, in my case they are not. Also after letting go of the gas at 1st, 2nd and maybe 3rd gear while moving deceleration is not very smooth, you can feel some jerkiness - very slight but I'm not sure if this is normal.

2. RPMs and hissing noise - I suspect they are connected as from my reading it could be a vacuum leak. Some data, with warm engine at 90C:

no A/C 625-650 RPM, 20-22% LOAD - you can feel stronger vibrations every second or so, hissing is accompanied by other noise that's hard to describe - something mechanical, belt related?



with A/C 925-950 RPM, 25-27% LOAD - car vibrations are much more even, no more of the "other noise" - or it's drowned by the engine


"other noise"


RPMs and LOADS were checked with my cheap OBDII scanner, I also checked for fault codes but couldn't find any.


Picture for @RobinA3 showing engine bay. I borrowed it from internet with purpose of labelling possible hoses that might leak.


That's about it, any advice would be very warmly welcomed, thanks!

RobinA3 said:

View attachment 205143

Is the noise coming from this stub pipe? Put your finger over it to see if its an open stub pipe.

Click to expand...

I'll have look tommorow morning and report back!

Success! At least partial, I've checked the pipe that you marked up but it didn't stop hissing when I put my finger over it, so I decided to investigate more and I took the engine cover off. To my surprise I found loose pipe covered in oil that I connected to nearby stub - hissing almost gone, I will clean it off the oil and check again.

That's how it looks like:


And close up of a stub pipe that you mentioned:


I'm thinking if the garage I left it at for an oil and air filter change didn't cocked up when they were doing it, they seemed a bit incompetent - 2hours for oil and filter change...