What happened?: My clutch pedal hit the floor during a shift and stuck in the depressed position. No return force on the clutch pedal, and I lost all clutch actuation. 79K miles on the car; 8.5 years in service.
What caused it?: Blown supply hose from the clutch master cylinder to slave cylinder. The rupture occurred under the car in the transmission tunnel, so I could see quite clearly how the hose had separated at the crimped union between a rubber section and the steel hard line.
What’s the repair?: Replace entire hose from the clutch master cylinder to the clutch slave cylinder (VAG part number 8K1721465G).
Procedure/steps: Replace hose starting in the engine cowl/plenum and continuing underneath the car on the transmission. Because of the routing and construction of the hard line section of the hose, a lot of stuff needs to come off in order to complete the repair. Here are the steps:
- Disconnect battery!
- Remove lower rear underbody tray. This is the extent of what you need to disassemble underneath the car (except for the hose itself)
- Remove all plenum covers between the engine/plenum bulkhead and firewall
- Remove the main weather stripping on bulkhead
- Remove washer fluid reservoir filler (one 13mm nut)
- Remove positive electrical terminal/junction from strut tower brace (10mm nut with a plastic acorn cap on it)
- Remove strut tower brace (yes, there’s one in there); four 13mm nuts on the strut towers and three 10mm bolts that secure the bulkhead to the brace itself.
- Disassemble and remove light grey E-box. The cover is held on by three Torx screws, then you remove the ECM by pushing the black plastic tabs back on both sides and pulling out. Once you have the ECM out of the way (the wiring harness is stiff, so it takes some force), remove the fuse/relay carrier from E-box. You’ll first remove two electrical connectors (red and white) that route into the firewall, as well as a red ground strap on the carrier itself. With those connectors removed, the fuse/relay carrier is removed by pushing back the retaining tabs on the gray housing itself. Peel back the ECM and relay carrier and set them on the engine (with harnesses still attached). You’ll also have to remove a second red ground strap on the body of the car itself.
- Remove wiper arms and wiper motor assembly (two 13mm nuts on wiper arms, and three 10mm bolts on wiper motor assembly)
- Remove E-box itself. Four Torx screws are easily accessed once the guts of the E-box are removed. The remaining wiring harness won’t allow you to fully remove the box, but you can maneuver it out of the way for the next steps.
- Remove steel shield on brake fluid reservoir. One Torx bolt.
- Remove brake fluid reservoir on master cylinder. Drain the reservoir as best you can, then push the retaining pin out of the hole to release the reservoir. Remove clutch master cylinder supply hose at this time as well. The reservoir pulls up and out of rubber grommets in the master cylinder.
- Remove both brake lines from master cylinder to ABS/ESP module and set aside. PLUG HOLES in the master cylinder and ABS/ESP module to minimize contamination.
- With the above parts removed, you can maneuver the bulkhead out of the way to give you a bit more space to work. The bulkhead can’t be removed without disconnecting the heater core hoses and AC lines at the firewall, and you’ll definitely want to NOT remove those if you don’t have to do so.
- Remove vacuum line from brake booster. It is just a rubber grommet that presses into the booster housing.
- Remove the brake booster by first unbolting the two long inner 12-point head bolts. Then, you’ll disconnect the brake pedal from the master cylinder rod/ball. This is a HUGE pain without the special tool (which I didn’t bother to get), so I’ve tried to annotate a picture of the mechanism so you can see how it works and how you might be able to get it apart. Essentially, there’s a rod from the brake master to the brake pedal, and it secures to the pedal with a steel ball that snaps into a white retainer clip. The wings of the white clip must be spread apart in order to remove the ball, which is extremely tricky with the limited space and zero ability to sight the clip. In the end, I removed the clip itself from the brake pedal using flathead screwdrivers and shims, and then removed the clip from the rod once I had more space to work. Once the booster is fully disconnected, it’ll pull right out of the plenum.
- Remove and reinstall clutch hose. There are two quick disconnect fittings on the hose that make it a breeze to attach at the master, and under the car at the slave cylinder.
- Reassemble the whole lot, in reverse.
- Refill brake fluid reservoir and bleed brakes. Remember, on these cars, the bleeding sequence is shortest-to-longest lines, so start with the driver front, then passenger front, driver rear, and passenger rear.
- Flush and bleed clutch system. To do this, open up the bleed screw on top of the clutch slave cylinder (underneath, on the transmission) and cycle through the pedal sweep, by hand, until the system is full of fluid and bubbles are gone. Then, just as you would with bleeding brakes, close the bleed screw and pump the pedal a few times, hold, then open the bleed screw. The whole process takes a while.
Overview of clutch hydraulic system
View of the part failure from under the car
Replacement part:
Removing connectors when disassembling E-box
Mid-disassembly
E-box with all the guts removed:
Removing brake booster
Disconnecting brake booster from brake pedal
New hose installed
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Originally Posted by jwr9152
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