Power Steering Pump Overhaul

[finnyracer]

The power steering pump on my 745i was leaking from behind the pulley so I decided to take the pump off to replace the seal. It turned out to be a complete overhaul of the pump. It also wasn’t as complex and difficult as I thought it would be and you can quite easily do this at home if you’re already spannering on your car.

Start by cleaning the pump and preparing a clean area to work in.

Remove the pulley flange, which is tapered and located with a key. The main roller bearing will be exposed, which is held in place with a circlip. Put the nut of the pulley flange back onto the shaft.
Remove the circlip and clamp the nut of the pulley shaft in a vice. Pull the bearing and shaft assembly out of the pump housing - the bearing should come out quite freely, it’s not a press fit. The main lip seal is exposed with a needle roller bearing press fitted into place behind it.





Turn the pump over and mount it in a press, or a drill press. Press down on the back plate against the internal spring and remove the circlip that secures the back plate in place.



The back plate make remain depressed in the housing when releasing the press. In this case support the pump in a vice with the main seal up, insert an extension through the seal and roller bearing, and tap gently. Allow the back plate and internal parts to fall into your hand. Be aware that you don’t lose any of the slide plates inside the pump.



Remove the rubber ‘O’ ring seals along with the white plastic ‘O’ ring supports. The white plastic ‘O’ rings are not Teflon seals, but are there to support the rubber ‘O’ rings against the pressure generated in the pump so that they don’t pop out. Note their position with the plastic ‘O’ ring supports towards the outsides of the pump housing.



Knock out the seal and the needle roller bearing. All the bearings and seals should be able to be sourced from any good bearing and seal shop.

Remove the circlip that holds the roller bearing on the shaft and press the shaft free. Replace with a new bearing, press it into place against the flange of the shaft and replace the circlip.



Press the needle roller bearing into place and then test fit by inserting the shaft and roller bearing into place. The shaft should turn freely in its new bearings. The circlip that holds the roller bearing in the housing must be fitted as well without force otherwise the shaft may be up against the needle roller bearing. The needle roller bearing might have to be pressed a bit more to make allowance for everything to fit nicely and turn freely.
Remove the shaft and roller bearing and press the new lip seal into place. Replace the shaft and roller bearing and secure in place with the circlip.

Turn the pump assembly over and support it in a vice.

Renew the ‘O’ ring seals along with the white plastic ‘O’ rings.

Ensure that the inside of the pump housing is clean and then put a few drops of ATF on the needle roller bearing at the bottom of the pump housing. Ensure that the locating pin is in the hole at the bottom of the housing.



Fit the first plate.



Fit the second plate and slide the pump rotor onto the shaft. Fit the slide plates into the rotor.



Lubricate the sides of the final plate and the ‘O’ rings with ATF to and push it into place. It's important to gently knock this whole assembly to ensure that the plates and the pump are flush up against one another. If a gap is left between any of the plates, then the fluid will escape and no fluid pressure will be created.



Fit the spring.



Lubricate the sides of the back plate with ATF and then press into place on the press and refit the circlip

Replace the brackets and flange and refit to the car.



Hold thumbs that all works without leaking again. If not, remove and send to ZF for an exchange pump. Which you probably should have done in the first place.

[madman2]

Great work and writeup. Thanks.Any idea how much an exchange pump would have cost? Thanks.

Sent from my SM-G935F using Tapatalk

[finnyracer]

Can't say for sure, but I got an exchange pump for my Audi RS2 Avant about two months ago for about $570.

[finnyracer]

So I installed the pump but could not get any pressure. I took it out and then removed the rear cover and the first section of the three internal plates to see if I could see anything obvious, which I couldn't. I pushed the plate back in place, which needed me to hit it with the back end of a hammer to drive it home and then replaced the cover. The next day I took it to ZF, where the pump was put on test and it worked perfectly.
The only think that I had done differently was to knock the rear plate home and the technician explained that if the two outer plates are not flush up against the pump, then the pump would not create pressure due to the fluid escaping between the plates.
I don't know if this was the case, but the pump was refitted and works perfectly now....without leaks. I've amended the rebuild procedure above.

[dodd7459]

nice write up. Should have replaced my seals while i had the chance. awww, you're in africa. No wonder you found an M e23. If you see anymore... I would love to get one shipped here to the states.

[adamcox27]

So I installed the pump but could not get any pressure. I took it out and then removed the rear cover and the first section of the three internal plates to see if I could see anything obvious, which I couldn't. I pushed the plate back in place, which needed me to hit it with the back end of a hammer to drive it home and then replaced the cover. The next day I took it to ZF, where the pump was put on test and it worked perfectly.
The only think that I had done differently was to knock the rear plate home and the technician explained that if the two outer plates are not flush up against the pump, then the pump would not create pressure due to the fluid escaping between the plates.
I don't know if this was the case, but the pump was refitted and works perfectly now....without leaks. I've amended the rebuild procedure above.

Would you mind saying where I could get replacement o-rings and bearing for this ZF pump ? I have an e23 that is fitted with such and needs a rebuild. Please PM me with any links I could source parts from. Thanks!

[finnyracer]

The bearings and seals were all over the counter parts that I got from bearing and seal retail specialists.

There are a number of specialist bearing retailers in South Africa, like Bearings International, and the needle roller bearing and roller bearing were FAG parts if I remember correctly. Likewise the seals were nothing out of the ordinary.

I'm sure you must have similar retail chains in Canada?