Replacing the steering box on a W123.
 

Just replaced a steering box for my daughter 83 240D.

My thoughts and steps on the job

Get the following

Rebuilt steering box
Power steering fluid (PSF), either Mercedes or another good brand.
Loctite blue
A pitman arm separator, can be loaned form O'reillys, Autozone etc.
Normal socket set and box wrenches.
Turkey baster
Power steering pump filter
PB Blaster to loosen the bolts
Allen sockets
A good long ratchet extension
Torque wrench that goes up to at least 150Ft Lb
35MM socket for the pitman arm nut.

--Jack the car up and place it on jack stands.
--Prior to starting this job spray the pitman arm with PB Blaster a couple of days before. Also the steering shaft linkage
--Remove the PSF filter
--Drain the PSF by sucking it out of the reservoir (clean it out with rags)and opening the steering box drain, 12MM wrench. Disconnect the low pressure return line at the upper clamp and allow to drain. Rotate the steering wheel from left to right stop, to remove the fluid.
--Prepare the new steering box by removing the hydraulic lines caps and removing the centering/drain screw as show in the picture below. You should get the box with it in it's centered position. Notice the slight indent in the
internal parts in the drain hole. That indent is where the center bolt goes.
--http://www.peachparts.com/shopforum/...4&d=1155749239
--Make a bolt out of a M8 X 1.0 X 20MM and grind the tip to a 45 degree point. The bolt will hold the unit in it's centered position while connecting it to the pitman arm.
--Make sure your steering wheel is centered, and lock it.
--Unbolt both Allen head bolts on the steering linkage, consider getting 2 new ones, you may strip the old ones getting them out.
--Slide the linkage up on the steering column shaft so the box input shaft is cleared.
--Disconnect the pitman arm with your pitman arm separator, mine required a 500FT LB impact wrench. The more you PB Blast it the better. (Consider separating the pitman arm first. If you can't separate it then you might want to drive it to a shop to do it.)
--Unbolt the 3 mounting bolts in the left wheel well. An assistant will be necessary. The box is heavy.
-- Remove the box from below.
--Mount the new box using Loctite blue on the bolt threads. Torque to specifications.
--Attach the steering shaft linkage and tighten to specs.
--Attach the pitman arm and torque to specs. Make sure you align the mark on the pitman arm with the mark on the steering box output shaft. Do not put pressure on the box internal stops while torquing. You may have to hold the pitman arm while torquing.
--attach the high pressure and low pressure lines to the box.
--IF FLUSHING THE BOX, DUE THE FOLLOWING
--keep the upper connection of the low pressure line unclamped. ( you will have to loosen the line into the pump and rotate it up so fluid does not come out.
--Add clean PSF to the reservoir.
--Place the return line hose in a clear gallon container and with a 1/2 gallon or a couple of quarts ready, have an assistant start the car. Pour the PSF into the reservoir so it does not empty, it disappears quickly. When the gallon container is full, shut off the engine. Do this until the fluid is clean Or not pink anymore ( if changing from ATF to PSF)
--Reconnect the low pressure line.
--Install the new filter
--Top off the system.
--Clean up the mess of spilled fluid. You will spill some PSF

Dave

Wow. So did the steering feel pretty good afterwards? Positive changes?

As usual from Dave, an excellent write-up on a seldom done task. You make it sound too easy.

My plan for the wagon's steering is to a swipe steering box from a parts car I have that was fairly low mileage and drove pretty well. Should I do that or get a rebuilt?

Ara.
Yes a definate improvement in the steering. The car was wondering down the road. You would move down the highway and put a slight input into the wheel to correct the movement out of the center of the lane. The car would continue to move out of the lane and you would have to correct back to the other side. Then the wheel did not feel like it would center back to it's normal center position. A definate flat spot in the steering due to over tightening the box.

R Leo

If you have a parts car I would try it. It can't hurt. Flush it well with new power steering fluid. And install it. If it is bad then you can always order a rebuilt.

Dave

This sounds familiar...

36 mm, not 35mm
 

On my 84 300D the pitman arm nut is 36mm, not 35mm. Just thought I'd save someone a trip to the store.

My dd has well over 300K on it and the original equipment box is still tight after adjusting.

Same here, up to 360k on original.

Charlie