Vauxhall Workshop Service and Repair Manuals

Brake Proportioning Valve, Check - Both Brake Circuits

Also in these vehicles the brake circuit is split diagonally.

Depending on the engine model or the regulations of the country, the rear brake circuit on saloons is controlled by brake proportioning valves screwed into the master cylinder.

Since each brake circuit is provided with a proportioning valve, both brake circuits must be checked.

All Models 35, 36, 45 and 46 are equipped with a load dependent tandem brake proportioning valve fitted to the vehicle underbody.

The valve is connected to the rear axle by a return spring and a retaining bracket.

The brake proportioning valve is adjusted with the vehicle unladen (curb weight, luggage compartment empty, fuel tank full, 1 person weighing approx. 75 kg/165 lbs. in driver's seat).

This operation can be carried out on an inspection stand without special tools.

Models 38 and 48 are equipped with a load dependent twin brake proportioning valve which is attached to the rear right of the vehicle underbody and connected to the rear spring by a return spring and a bracket.

The brake proportioning valve is also adjusted with the vehicle unladen (curb weight, luggage compartment empty, fuel tank full, 1 person weighing approx. 75 kg/165 lbs.

in driver's seat).

This operation can be carried out on an inspection stand without special tools.

The brake proportioning valve is checked using Brake Gauge MKM-558 or a comparable tester.

When checking, ensure that hydraulic line pressure can be measured simultaneously, but diagonally, on front and rear axles.

Remove bleeder valve and mount corresponding adapter for tester connection on brake caliper.

Unscrew bleeder valve from brake cylinder diagonally opposite brake caliper already connected and mount adapter and corresponding coupling for connecting tester.

Note:

Observe manufacturer's instructions before using tester.

Illus. C 0525 shows "drum brake" model. The operation for "disc hub" model is identical.

Pressure Check on All Models Except 35, 36, 38, 45, 46 and 48

Build up pressure on pressure gauge of brake caliper by pressing firmly on brake pedal several times. Value indicated on pressure gauge for brake caliper is not regulated and represents actual brake line pressure.

Adjust pressure gauge of brake caliper to test values given and read test value from pressure gauge on rear axle. Values must agree with those in table below. Do not build up pressure on brake caliper above 10 000 kPa/100 bar, otherwise pressure gauge on rear axle will give false readings.

Engine or model up to Model  Year 86

Reference number for gradient and switching pressure on valve housing

Input pressure read on manometer at front axle in kPa (bar)

Output pressure read on manometer at rear axle in kPa (bar)

12 SC Export,

500 (5)

500 (5)

C 13 N,

3/35

6000 (60)

4250 ± 200

13 N with AT,

13 SC alle

(42.5 ±2)

10 000 (100)

5450 ± 400

(54.5 ± 4)

16 SH,

500 (5)

500 (5)

16 D, 16 DA,

18 E,

3/30

6000 (60)

3900 ± 200

(39 ± 2)

C 18 NE

10 000 (100)

5100 ± 300

(51 ± 3)

Engine type as of Model Year 88

Reference number for gradient and switching pressure on valve housing

Input pressure read on manometer  at front axle in kPa (bar)

Output pressure read on manometer at rear axle in kPa (bar)

12 SC, 12 NV,13, 13 S, A 13 S, (S) 13 ST,

E 13 GV,

C 13 N, 14 NV, C 14 NZ

C 13 N, 14 NV, C 14 NZ

all also with AT

3/45

500 (5)

6000 (60)

10 000 (100)

500 (5)

4950 ± 200

(49.5 ± 2)

6150 ± 400

(61.5 ± 4)

C 16 LZ

3/30

500 (5)

6000 (60)

10 000 (100)

500 (5)

3900 ± 200

(39 ± 2)

5100 ± 300

(51 ± 3)

15 LV, 15 DTR,

16 DA, 16 SV,

E 16 NZ,

C 16 NZ, 17 DT,

18 SE, E 18 NV,

S 18 NV,

20 SE, 20 SER,

20 SEH,

C 20 NE, 20 NE,

C 20 LZ, 17 D

3/40

500 (5)

6000 (60)

10 000 (100)

500 (5)

4600 ± 200

(46 ± 2)

5800 ñ 300

(58 ñ 3)

20 XE, C 20 XE,

4.5/20

500 (5)

6000 (60)

10 000 (100)

500 (5)

3800 ± 200

(38 ± 2)

5600 ± 300

(56 ± 3)

Reference

Input pressure

Output pressure

number for

read on mano

read on mano-

Valve

valve

meter at front

meter at rear

housing

axle in

axle in

kPa (bar)

kPa (bar)

Tandem

6000 (60)

3900 to 4200

(39 to 42)

(load

6/5

dependent

10 000 (100)

5700 to 6100

(57 to 61)

Twin

6000 (60)

3900 to 4200

(39 to 42)

(load

dependent)

8/5

10 000 (100)

5700 to 6100

(57 to 61)

The switching pressure and gradient reference number are located on the valve housing.

Illus. C 0607 shows a tandem load dependent valve.

Illus. C 2151 shows a twin load dependent brake proportioning valve.

The housing of the load dependent twin brake proportioning valve contains two identical regulating units, seated parallel and working independently of one another. They are subjected to spring pressure by a common lever.

Thus both brake circuits to the rear axle are regulated independently of one another, so that if one circuit ceases to function the other intact brake circuit continues to function normally.

Until switching pressure is reached, input and output pressure are the same in the twin regulator. When pressure increases further on the input side, the output pressure is reduced by a specific ratio in relation to the input pressure.

Remove tester from brake circuit already checked and repeat check on other brake circuit. Subsequently remove tester.

Remove pressure line from brake caliper and wheel cylinder.

Unscrew adapters and mount bleeder valves.

Bleed brake system.

See operation "Brake System, Bleed".

Check brake system for leaks.

See operation in this group.

Load Dependent Brake Proportioning Valve, Check Function or Adjust

To do this, stand vehicle either on ground or on inspection stand - not on a vehicle lift with outriggers.

Depress brake pedal firmly and release quickly. Lever on brake proportioning valve must move (2nd mechanic required).

If the lever does not move, replace brake proportioning valve.

Adjust brake proportioning valve.

If test pressure read off at rear axle is too high, ease

tension on return spring until required test pressure is reached.

If test pressure read off at rear axle is too low, tension return spring until required test pressure is reached.

Important: Do not adjust brake proportioning valve while brake system is under load.

Illus. C 0555 shows adjustment on tandem brake proportioning valve.

Illus. C 2128 shows adjustment on twin brake proportioning valve.