Line Pressure Measurement
2531 Pressure Gauge:
1. Check/top-up oil level.
2. Connect Pressure Gauge 2531 to transmission.
- Attach pressure gauge to door window.
- Remove front plug on transmission and connect nipple P/N 5074.
- Connect pressure gauge hose to nipple.
3. Start engine and allow to idle in position N. Check idle speed see below:
Engine Type: Idle Speed r/s (r/min):
D24 (Low Idle) 12,5 (750)
B21 MPG, LH 12,5 (750)
Other markets 15,0 (900)
B23E, B28F - 1980 15,8 (950)
4. Depress brake pedal. Move gear selector to position D and record line pressure.
5. Move gear selector to position R and record line pressure.
Line Pressure Too High, Probable causes:
- throttle valve clip dropped off
- throttle valve incorrectly adjusted
- primary regulator valve seized. Check as follows: Rev up engine. If pressure increases proportionally to engine speed, valve has seized.
- throttle valve seized. Check as follows: Allow engine to idle in position N. Pull out throttle valve by hand (without moving throttle). If line pressure does not increase throttle valve has seized.
- shift valves seized
- cut back valve seized
Recondition valve body assembly if shift valves have seized. If no fault is found, recondition transmission.
No Rearward Drive (No Line Pressure), Probable Causes:
- primary regulator valve defective
- 2-3 shift valve defective
- reverse gear sequence valve defective
- C2 accumulator piston defective
- center support bolts loose.
Line Pressure Too Low, Probable Causes:
- seized primary or throttle valve.
- Check according to "Line pressure too high".
If test shows values are OK, low pressure may be caused by defective bypass valve (not fitted to late type BW55 transmissions) or oil pump (noisy). Alternatively oil filter may be blocked or accumulator pistons may be defective.
Line Pressure Correct At First But Drops After A Few Seconds, Probable cause:
Defective secondary regulator valve. If early type valve is fitted replace with new type. Recondition valve body if valves are found to be defective.