Steering Box Replacement

Article by: Johan

Article applies to: all E32 and E34 cars with a straight 6 engine. The procedure is similar for models with the v8 and v12 only there is less room to work and more stuff to remove.

Problem: After adjusting and readjusting the box you will finally end up at a point where there is no more readjusting to be done.

The only possible settings are sloppy steering or a steering wheel that won’t return to the straight ahead position on it’s own. In my case I probably messed it up myself.

I readjusted the box to the last position it would still self center to get rid of the play in my steering.

But it turned out the play was caused by a loose pinch bolt on the drop arm. Oops…another expensive lesson to be learned.

Additional information: I replaced the non-Servotronic steering box in my 735i with a Servotronic box from a 750i.

The Servotronic is a very easy retrofit as the wiring is already present in the car.

The wiring to the box was tie-wrapped under the brake bomb and the yellow control module plugs are behind the driver side foot well speaker panel.

As you can see the left (1991 750i box 190k km) box has a torque convertor for the Servotronic while the box on the right (1986 735i >300k km) doesn’t.

The servotronic control unit located in the driver’s side foot well behind the speaker:

Picture from Cor’s 750i.

The 735i doesn’t have the sensor lock module for the air conditioner.

In case you are wondering what Servotronic is: it’s a system designed by ZF that regulates the amount of power assist at various speeds.

When you park the car at low speeds the steering is fully assisted and very light.

When you are cruising on the highway at high speeds the assist is very low and the steering will be firm.

Installing a 735i box into a 750i should also be possible.

But the 750i has mounting points for the heat shield so you might have to be a bit creative to mount the heat shield.

If you are getting a replacement box make sure you get the drop arm with the box.

The diameter of the output shaft from the 1991 box was a bit larger then the one on the 1986 box. Something you don’t want to find out with the box out of the car.

Let’s get wrenching:

First jack up the car. But you probably guessed that already.

To drain the hydraulic fluid I decided to just unscrew the line from the reservoir to the hydraulic pump instead of emptying the reservoir with a syringe.

In my case the fluid was about 70% ATF 30% Pentosin.

Let’s start by undoing the cross coupling at the steering box.

Then undo the tie rod from the steering box drop arm. In my case it refused to budge. So I undid the drop arm from the box.

Then undo the short vertical bolt and the long horizontal bolt.

And the picture I “borrowed” from Sean:

Inside the hole near the Pentosin leak is the vertical mounting bolt.

Here is a view from the top with the engine removed (from my 735iL parts car).

Now to reach the nut on the horizontal bolt you must undo the engine mount and lift the engine a bit according to the Bentley manual.

I did not feel like doing that so I maneuvered in a box wrench instead. This was fidgity but a lot less work then removing the engine mount.

Now all you have to do is remove the fluid lines and maneuver the box out from under the car.

As the drop arm refused to leave the center tierod and the drop arm didn’t fit on my replacement steering box I removed it all together.

First I threatened the drop arm with a hammer. When that didn’t help I used the hammer to hit it a couple of times. That did do the trick 🙂

That’s all there is to that. Now go and put the box back on the car

As I was running contaminated ATF/Pentosin I decided to replace all the fluid I could with Pentosin.

On my car there is no label telling me which fluid to use. On the older e23 with the same hydraulic brake booster Pentosin was used.

But some e32s seem to have ATF in the system. As Pentosin is less detergent I figured it would be nice for the old seals in the hydraulic system.

Plus I recently read a posting from Rainman on the Roadfly board that BMW recommends replacing ATF with Pentosin in colder climates.

So it surely can’t hurt. Using LHM is also an option as it’s pretty much the same fluid. And while I was at it I also replaced the filter in the system.

Cars without LAD (Self-Leveling) and a hydraulic brake booster don’t have a filter in the reservoir.

First remove the clip holding the screen.

Then pull out the screen.

Remove the washer and the spring.

Now you can remove the oil-strainer that contains the filter cartridge.

The filter is located on the underside of the oil strainer.

Be careful removing the black rubber ring if you are reusing it. In my case it was rather fragile as the rubber turned hard.

All the parts nicely laid out on the work bench. (So what if someone drove over the WD40 can ;-))

You can ignore the small rings on the workbench.

I was doing an oil change at the same time and the rings belong to the engine oil filter kit.

The new filter seems a bit cleaner then the old one.

Reinstall the filter stuff and fill up the system with fresh ATF or Pentosin/LHM.

Then comes the hard part: you have to start the car and listen to the hydraulic pump that sounds like it’s dying or dead already.

This really scared me so I went to ask the kind people on the Roadfly e32 board. According to Max F. and Rainman (thanks guys!) the noises are normal.

Also the Pentosin will foam a bit while the air is being bled from the system.

To help bleed the air from the system turn the steering wheel slowly from lock to lock about four times and pump the brakes every now and them.

After most of the noise is gone take it for a short ride. I my case that removed all the noises.

Total amount of parts and cost:

The gasket rings are on the banjo bolts that connect the hydraulic hoses to the pump and the steering box.

I must admit I lied a bit. As I forgot to order them I didn’t replace the gasket rings . . . but I wanted to.

Honestly! I’m keeping my fingers crossed the old ones won’t cause leakage.

Keep in mind these parts work for my 1987 735i, but there are lots of differences in steering boxes and fluid filters.

So double check the parts before you order them.

I won’t tell you what the total costs are because no one will believe me if I tell them how little I paid for the second hand steering box. 🙂

Total amount of time: All and all it took me about 5 hours to do.

Skills needed/difficulty level: Not the easiest job especially when the tie rods are against you. But a for a skilled DIY mechanic it’ll be a piece of cake on the straight 6 E32s.

Satisfactory level after the job done: Very! The steering is now very light when parking and stiff at high speeds.

There is still a bit of play that has to be adjusted. That should be OK as the adjustment screws seems untouched.

After that I’ll have a wheel alignment done as the car pulls slightly to the right. Nothing to worry about I guess but with fairly new tires in front I’m not taking any chances.

We all know what those babies cost!