ZF Steering Rack, just finished rebuinding it, now what?

[Dave A.]

I rebuilt my ZF Power steering rack by replacing all the seals. All went OK
with not too much difficulty. It was in good shape internally, no groves or
flat spots. I think I got it back together the way it was, but the proof
will be when I start the engine.

Now that it's together I am wondering if I should have filled the main tube
up to the top . I did add a lot of new power steering fluid but there must
be some air in the cylinder, and for sure the hydraulic lines. Will the air
self bleed out or do I need to perform a bleed prior to installation. Don't
see any ports or opening that would facilitate a bleed so I'm not sure how
to proceed.

I could remove the lines at the control head, place them in fluid container
and operate the rod, vacuum would pull fluid and should fill the main body
completely, one side at a time.


OR will the power steering pump charge the system and remove the air?

 

[James Sweet]

I rebuilt my ZF Power steering rack by replacing all the seals. All went OK
with not too much difficulty. It was in good shape internally, no groves or
flat spots. I think I got it back together the way it was, but the proof
will be when I start the engine.

Now that it's together I am wondering if I should have filled the main tube
up to the top . I did add a lot of new power steering fluid but there must
be some air in the cylinder, and for sure the hydraulic lines. Will the air
self bleed out or do I need to perform a bleed prior to installation. Don't
see any ports or opening that would facilitate a bleed so I'm not sure how
to proceed.

I could remove the lines at the control head, place them in fluid container
and operate the rod, vacuum would pull fluid and should fill the main body
completely, one side at a time.


OR will the power steering pump charge the system and remove the air?

The fluid circulates in a loop, it'll bleed itself. Just crank the wheel
lock to lock a few times with the engine running, ideally on soft ground to
be easy on your tires.

 

[Mike F]

I rebuilt my ZF Power steering rack by replacing all the seals. All went OK
with not too much difficulty. It was in good shape internally, no groves or
flat spots. I think I got it back together the way it was, but the proof
will be when I start the engine.

Now that it's together I am wondering if I should have filled the main tube
up to the top . I did add a lot of new power steering fluid but there must
be some air in the cylinder, and for sure the hydraulic lines. Will the air
self bleed out or do I need to perform a bleed prior to installation. Don't
see any ports or opening that would facilitate a bleed so I'm not sure how
to proceed.

I could remove the lines at the control head, place them in fluid container
and operate the rod, vacuum would pull fluid and should fill the main body
completely, one side at a time.

OR will the power steering pump charge the system and remove the air?

It's probably too late now, but with the front wheels raised you should
first turn the rack lock to lock a couple of times to get as much air
out that way before starting it. Then you should start it and repeat
the above. Obviously, make sure that the level is kept topped up as the
air comes out. It's not too big of a deal if you don't do it this way,
the air will eventually come out by itself, this way not so much air is
beaten into the fluid, so it comes out more quickly. The steering can
be noisy with aerated fluid.

 

[John B]

I rebuilt my ZF Power steering rack by replacing all the seals. All went OK
with not too much difficulty. It was in good shape internally, no groves or
flat spots. I think I got it back together the way it was, but the proof
will be when I start the engine.

Now that it's together I am wondering if I should have filled the main tube
up to the top . I did add a lot of new power steering fluid but there must
be some air in the cylinder, and for sure the hydraulic lines. Will the air
self bleed out or do I need to perform a bleed prior to installation. Don't
see any ports or opening that would facilitate a bleed so I'm not sure how
to proceed.

I could remove the lines at the control head, place them in fluid container
and operate the rod, vacuum would pull fluid and should fill the main body
completely, one side at a time.


OR will the power steering pump charge the system and remove the air?

Where did you find the parts to repair your rack?