Brake Booster Check Valve - BMW 5251 Service Manual

Brakes
The brake booster is mounted to the bulkhead on driver's side
of the engine compartment, directly behind the brake master
cylinder. Intake manifold vacuum acts on a large diaphragm
in the brake booster to reduce brake pedal effort.
Brake booster check valve
The checlc valve in the bralte booster vacuum line prevents
contamination from engine backfires and other sources from
entering the bralte booster.
Location of check valve varies, depending on year and mod-
el.
4
6-cylinder models (528i):
1. Intake manifold
2 Hose clamp
3. Vacuum line
4. Upper hose bracket
5. Grommet
6. From 911998: Check valve in grommet in booster.
Remove left ventilation filter housing for access.
7. To 911 998: Check valve in vacuum hose. Remove left
ventilation filter housing, peel back trim rubber below
housing and unclip upper hose brackets to access hose
clamps and valve.
8. Lower hose bracket
9. Brake master cylinder
10. Brake booster
<
6-cylinder models (525i, 530i): Remove left ventilation filter
housing to access checlc valve.
1. Vacuum hose
2. Hose clamp
3. Hose bracket
4. Check valve in grommet in booster
5. Braite master cylinder
6. Grommet
7. Brake booster
4
V-8 models (540i) to 911998: Check valve (arrow) in vacuum
line behind left cylinder head.
-
V-8 models (540i) from 911998: Checkvalve in brake booster.
Remove left ventilation filter housing to access valve.