Power Steering Pump: Testing and Inspection
Diagnosis by SymptomProgrammed Repairs for the 765.9 Steering Gear and Power Steering Pump Models 61-67 and 161-167:
Condition: Insufficient power assistance at left full lock, spongy.
Application: All Models
Cause: Air cushion in steering housing. This occurs in the most cases after performing repairs and incorrectly filling power steering pump/tandem pump. Service and Repair
Remedy: Drive car until oil in power steering pump/tandem pump is at normal operating temperature. Then park car at full right lock. Raise car at front axle with vehicle jack. Wait approx. 10 minutes. Run engine at idle and with the car on the ground, turn steering several times from full left to full right lock. Any remaining air cushion, detectable only when turning the steering rapidly to full left/right lock, will be slowly eliminated by the oil circulation (100-200 km).
Condition: Oil flows out at steering gear adjusting screw.
Application: Models 124 and 201
Cause: Polyamide ring on lock nut does not provide adequate seal.
Remedy: Replace lock nut, part No. 001 990 70 51
- To do this, remove steering gear on cars with gasoline engines. Remove air filter housing complete on cars with diesel engines.
- Mark position of adjusting screw with notches (arrows).
- Replace lock nut without altering position of adjusting screw.
- Tighten lock nut to 65 Nm.
NOTE: If the adjusting screw has been inadvertently turned, reset friction value of steering gear. Service and Repair
Condition Oil flows out through breather cap of power steering pump.
Application: Models 124 and 201
Cause: Reservoir incorrectly filled (too high) and/or no breather in protective tube.
Remedy: Correct the oil level and/or drill breather (arrow) according to sizes indicated in image.
Condition: Oil flows Out through radial seal ring in pitman arm shaft/bearing cover.
Application: Models 124 and 201
Cause: Faulty seals (Gotze, Pionier-Laura).
Pressure peaks in lubricating circuit (since 3/89 relief restrictor fitted).
Remedy: Install new seal (Freudenberg - color blue). Service and Repair
Condition: Oil flows out through radial seal ring in steering shaft bearing cover.
Application: Models 124 and 201
Cause: Faulty seals (Gotze, Pionier-Laura).
Pressure peaks in lubricating circuit (since 3/89 relief restrictor fitted).
Remedy: Install new seal (Freudenberg - color blue).
Up to 9/87 seal can be replaced without any problem (press seal into bearing cover from outside. Recognizable from locking ring fitted).
As of 10/87 the steering gear must be disassembled. Seal can only be replaced if complete special tool available. Tools and Equipment
Condition: Knocking noise from steering gear when driving on uneven road surfaces and steering slightly turned.
Application All Models
Cause: Excessive play in steering gear causing tooth flanks to strike against each other.
Remedy: Set steering gear friction value. Service and Repair
Condition: Steering pressure point on left or right lock.
Application: Model 140
Cause: Thrust washer on control valve sticks. This can be detected as play during brief steering movements when vehicle is stationary.
Remedy: Install new steering gear (production number above 92 73400), The production number is stamped on the flat surface of the steering housing.
Condition: Leaking power steering pump at seal of bearing flange Model or at bearing flange
Application: Models 124 and 201
Cause: Severe vibrations from belt drive and engine (particularly diesel engine.
Remedy: Install ZF power steering pump with reinforced bearing flange (production breakpoint 11/89).
Check that the power steering pump is filled correctly. Service and Repair
Check connections on oil hoses for leaks.