Preamble: When I was replacing the cam tensioner/valve cover gaskets on my car, the brittle vaccum hose coming out of the bottom of the 3-way elbow that the valve cover and PCV go into (hose #9 in the ETKA diagram below) crumbled in my hands. After doing some researching, apparently I'm not the only one this has happened to and this is a common failure from a poor material selection and oil soak combined with engine heat. Of all of the posts that I found, the only solutions that people posted were a revamp of the vaccum system/elimination of some hoses, or a repair that involved having to buy a whole new plastic "T" fitting under the intake manifold (#5 in the diagram, like a $35 part from ECS IIRC). Most threads I found had people saying that the hose and T-fitting were fused, and that is why you couldn't replace just the hose. When I went to the dealer to order just the hose, I was brought out a metal hose (the original was stiff plastic and a different shape) apparently from an update/revision, which would also require that I replace the T-fitting with a different version that would connect to the metal hose. Plus, the hose itself was priced something ridiculous, like $90. Anywho, I went for a DIY route, and I'm happy to say that I found a simple solution that required less than $10 in parts and you don't have to take off the intake manifold. You literally just replace the missing hose section with heater tubing and a male-to-male coupling. Even though it's simple, I'll make a noob friendly writeup since I took the time to take pictures.
NOTES: The ETKA diagram is a generic one for the 1.8t and your motor may not look exactly like that. For example, the metal elbow coming off of my valve cover faced the rear, not the right side of the car, and the main hose in question (#9) wasn't shaped like that on mine. The intake manifold doesn't have to come off, and that's how this writeup was written, though it would definitely be easier to get the clip off of the bottom of hose #2 with the intake manifold out of the way. You choose.
- LONG flathead screwdriver
- Smaller flathead (for electrical connectors)
- Phillips screwdriver
- 5mm allen or hex key
- Approx. 1.5' of 3/4" heater hose (you could probably get away with 12", I didn't measure after I trimmed)
- 3/4" male-to-male hose coupler kit (I purchased both the hose and coupler from Autozone)
- Simple worm-style hose clamps from hardware or auto store (note: you may not need 1 or 2 of the bigger clamps that I got, because I may have lost one of the re-usable Audi clamps)
And if your coupler kit doesn't come with clamps, then you'll want 2 more 1-1/4" or 1-1/2" clamps
-Just to give an overview, the goal is to get this hose assembly out so that we can replace the yellow (circled) hose (which is cut in half in this picture.)
Yellow is #9 in ETKA, Blue is #2, Red is #24, Green is #10. From here on out I will refer to them by those colors.
-Start by taking the 3-way elbow off of the back of the head/PCV, and disconnect the small hose from the junction off of the head (red circle). I use locking vise grips for the re-usable clamps. Disconnect the sensor with the orange arrow.
- Back in that area there is a zip-tie wire fastener that clips into a tab on the yellow tube. If this tab hasn't already crumbled off, you can get the zip-tie clip out of the hole by squeezing the tabs with needle-nose pliers.
- We now take off the throttle body. Unclip the electrical connector on the bottom of the TB. Loosen off the big clamp. Get the big hose off the front (it might help to grab the hose and push and pull to flex the hose off of the lip). Undo the 4 hex bolts holding the TB on.
- Unmount the coolant reservoir. There's a single phillips screw on the front, and the back in held in place with two tabs. To get the tank out of the two tabs, you need to lift the front of the reservoir and pull up and towards you. This is a little tricky with all of the hoses connected. Disconnect the electrical connector on the bottom of the reservoir, and rest it out of the way towards the front of the car.
- Unhook the green hose, which is on the driver's side of the intake manifold. Unhook the senor with the arrow.
- Unhook this green sensor (we're trying to make as much room as possible to work with down there, which isn't much.)
- Now the hardest part of this all, remove the clip holding on the blue hard pipe so that you can pull it straight up and out. Below are pictures of the clip, the pipe and the location. Because there's no room to work with, the clip is TOUGH to get off. I started out by going at it from above, through the slot between the intake manifold runners with the LONG screwdriver. To get in behind the clip to get it started, I used a little mallet. Once the blade was in, I twisted the screwdriver to pull it out a little. I also got vice grips on it from the side, but IIRC I finally got it off with some finagling with the screwdriver from above. Putting this back on is fun too. Once the clip is off, pull straight up and the hose just slides out.
- Now that those 4 connections (yellow, red, blue and green) are off, you need to wiggle the assembly out from under there. I had to cut the yellow pipe in half (it's the one getting replaced) to get rid of some of the bends and make it easier to pull out. Leave the last bend on the yellow pipe though, because it's going to be beneficial when trying to twist the pipe to break whatever bonding may have occurred at the T fitting. It should look something like this (the same picture I posted at the beginning).
- Now, to get the old hose off. I was expecting this to be bonded like everyone was saying, and I thought I'd probably have to go pay for the Audi specific parts at this point, but to my surprise, this part was really easy. It was really cold in the garage, so that may have helped, but I just grabbed the yellow tube and twisted. It popped and broke whatever bonding may have occurred. Once the bond was broken and the pipe was spinning freely, I got a lighter and heated up the hose at the fitting. Since the hose was relatively flexible material and the T fitting was hard plastic, I wasn't too worried about melting the fitting. With a little heat, the hose pulled right off the barbed fitting!
- On with the new hose and clamp.
- Installation is the reverse of this. Once you wiggle the hose assembly back up in there, cut the hose to the right length and install the male-to-male coupler, which goes into the bottom of the 3-way elbow. Getting that hard clip back on the bottom hose under the intake mani is a pain. I got it situated with my hand, and used a screwdriver and a mallet from the side to get it seated. Also, take note of the throttle body orientation when reinstalling it (reference the pic below). Other than that, just re-install everything and pat yourself on the back for saving $150+ in Audi parts, and at least the same amount on labor!
Edit: This should probably be in the tech section, if someone wants to relocate it.