Steering pump adjustment

[privatecollection]

Good afternoon,

I have Mercedes 280SL Pagoda from 1969 and some weeks ago i have small oil leak in Steering Pump.
They have taked pump from car and after have changed "Power Steering pump oil seal ". They have installed steering pump and they said me that dont have any adjustment but now steering it is heavier than normal and i dont know what to do.

Do you know if steering pump have any adjustment or any special attention when we reinstall it ?
Before this, steering pump is working very good, only with small oil leak.

Thanks.

Best regards,

Vasco

[teahead]

ask them if they tested the pressure coming out of the pump.  What psi/bar?

[MikeSimon]

There is no adjustment in the p/s pump. The pumping element creates a flow/pressure against an internal spring loaded valve which controls the output. If they assembled something wrong in the pumping element (vanes upside down, e.g. or missing a vane or broken spring) the pump may not produce the flow/pressure necessary. Only way to really test it is off the vehicle on a hydraulic test stand.
The pump will provide an increasing flow up to a certain rpm at which the flow will remain constant. When the output line is closed ( steering at full turn), the pump will go into "relief" at a certain max pressure. The service manual should state these numbers.

[Tyler S]

I have found that a simple fluid change can result in heavier steering effort. Usually when replacing thin ATF that has been in the system for some time.

[Shvegel]

I believe there is a bleeding procedure involving a bleed screw on the steering rack itself.

[MikeSimon]

If there is air in the system, the fluid in the pump reservoir will show a "foamy" consistency. Usually the system in the W113 "bleeds itself" by turning the wheel from end to end a few times.

[NYC-MB280SL]

A newly rebuilt pump needs to be bled when it is installed.

A high end re builder, C&M Hydraulics, describes the procedure on their website--

http://candmhydraulics.com/bleeding090.pdf

[MikeSimon]

Don't really care what the "high-end" rebuilder's opinion is, but the pump itself does not trap air. The air is in the lines and in the steering box. The pump purges any air inside when it pumps.
If the system has "high points" where air can be trapped, special bleeding may be necessary. Otherwise, the air in the system gets pumped into the reservoir.
Some steering systems do not have "bleed screws". Don't know about our SL, but when I had the pump off the last time and had it checked in our engineering lab (I worked for Vickers) I did not bleed it after reinstallation.

[Tyler S]

There is in fact a bleed screw on the top of the steering box. Has a rubber cap. Just below the cabin firewall drain bulb. However I did not need to bleed anything when changing my power steering pump. Only when I rebuilt the steering box. Gravity bleed it while keeping the reservoir full. No need to have the car running. Crack it loose till the bubbles disappear. Some cars have a pipe connected here for the idle up actuator. This may or may not fix your issue.