Removing and installing control unit and hydraulic unit, diesel engine — VW

🧭 Before you start

Record the control unit code and radio code, disconnect the battery and clear the access from above and below. Unplug the control unit, depress the pedal at least 60 mm, drain the left-hand bleeders and close them. Mark, undo and plug every brake line, lift the unit out of its dampers, unbolt its bracket and remove it. Fit the new unit, removing each plug only as its line goes on, then bleed the brakes, code the radio and code J104.

Fits: platform codes AU1, BX5

• Opens: brake fluid

Don't miss

• Read out and note the existing control unit code before disconnecting anything.
• Do not bend the brake lines around the hydraulic unit and keep brake fluid off the contacts.
• Mark every brake line and plug lines and holes straight away with set 1H0 698 311 A.
• Remove the new unit's sealing plugs only as each line is fitted, or it may not fill and bleed.
• Do not push the rubber dampers out of the bracket when fitting.
• Bleed the brakes, code the radio and code J104 afterwards.

Written for this job from the workshop steps below · TorqFix editorial.

📋 Procedure

1. ⚠ Do not bend the brake lines in the area of the ABS hydraulic unit N55 — Read out and note the existing control unit code.
2. If vehicle has a coded radio, note radio code or, if necessary, request it.
3. Disconnect battery Electrical system27Battery; Disconnecting and reconnecting battery.
4. Remove engine cover panel 10Engine cover panel; Removing and installing engine cover panel.
5. Remove noise insulation General body repairs, exterior66Noise insulation; Assembly overview - noise insulation.

6. If driveshaft heat shield is fitted, remove it (arrows)Running gear, axles, steering40Drive shafts; Removing and installing driveshaft heat shield.
7. Remove front exhaust pipe 26Exhaust pipes and silencers; Removing and installing front exhaust pipe.
8. Unscrew both nuts (arrows) for coolant line retainers (1) from longitudinal member and from plenum chamber bulkhead.
9. Pull retainers off studs, and pull down coolant line as far as possible.
10. Remove heat shield (1) if present.
11. To do this, unclip heat shield (1) from bracket (2)(arrow).
12. In vehicles with heat shield, remove heat shield .
13. Unclip line guide.
14. Push down locking slide (arrow A).
15. Release catch in direction of (arrow B).
16. Pull off electrical connector (1).
17. Apply brake pedal depressorV.A.G 1869/2.
18. Connect hose of bleeder bottle (1) to bleeder valve of front left brake caliper.
19. Open bleeder valve.
20. Connect hose of bleeder bottle (1) to bleeder valve of rear left brake caliper.
21. Open bleeder valve.
22. Depress brake pedal at least 60 mm using brake pedal depressorV.A.G 1869/2.
23. Close front left and rear left bleeder valves.
24. Do not remove brake pedal depressorV.A.G 1869/2.
25. Place sufficiently lint-free cloths under ABS control unit J104 and ABS hydraulic unit N55. [Note: Ensure no brake fluid gets onto contacts.]
26. Pull cover off bulkhead and unclip brake lines.
27. First, mark brake lines (5) and (6).
28. Unscrew brake lines (5) and (6) from ABS hydraulic unit N55.
29. Immediately seal brake lines and threaded holes with sealing plugs from repair set Part No. 1H0 698 311 A.
30. Mark, unscrew and seal remaining brake lines (brake calipers).
31. Pull ABS hydraulic unit N55 together with ABS control unit J104 upwards out of dampers (arrow).
32. Carefully set down ABS hydraulic unit N55 together with ABS control unit J104 in engine compartment.
33. ⚠ Set down ABS hydraulic unit N55 together with ABS control unit J104 such that it cannot fall down. — Raise vehicle.
34. Unbolt bracket from ABS hydraulic unit N55 in vehicle (arrows).
35. Guide ABS hydraulic unit N55 out of vehicle. [Note: Do not remove sealing plugs from new ABS hydraulic unit N55 until respective brake line is about to be installed.If sealing plugs are removed too early from the ABS hydraulic unit N55, brake fluid can escape, and it can then no longer be guaranteed that the unit can be sufficiently filled and bled.When installing the ABS hydraulic unit N55, ensure that the rubber dampers are not pressed out of the bracket.]
36. Remove brake pedal depressorV.A.G 1869/2.
37. Bleed brake system .
38. Code radio.
39. Code ABS control unit J104 using .

Other VW procedures

• Removing engine · 41 torque figures
• Removing and installing camshaft – VW Golf Cabriolet · 47 torque figures
• Adjusting valve timing – VW Passat B5 · 83 torque figures
• Removing and installing camshafts – VW Passat B6 · 39 torque figures
• Removing and installing coolant pump · 53 torque figures
• Checking fuel pump(s) – VW PG
• Dismantling and assembling selector mechanism on vehicles without key withdrawal lock up to 06.99
• Checking Lambda probe heating before catalyst
• Pressing front wheel bearing out and in with wheel bearing housing installed, 13" running gear
• Checking signals from brake light switch and brake pedal switch