2003 Z4 Hydraulic Power Steering Conversion

1

10Terp

Member
 Virginia, USA (DC-area)
Hello all. Haven't posted here in a while. Since my last post I've had my first kid so time has certainly been at a premium recently. I have been itching to get back to the Z4 and have been reading and researching doing a hydraulic power steering conversion upgrade. I know there are several threads on this already, so I hope this thread will add to the already collective knowledge that is out there.

A local junkyard got in a 2002 325CI earlier in the week and I decided to take a day off and go pull the power steering system out of it. Here's what I came home with:

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Interestingly, I'm pretty sure this car had a remanufactured purple tag rack. It has some markings on it that indicate it's remanufactured, and it appears another tag was riveted on. It's also very clean. Originally I was concerned it was a silver tag rack, but several things point to it being a purple tag: 3 turns lock to lock, November 2001 manufacture date, and the casting numbers on the body are the same as several ebay purple tag racks I looked up. The outer tie rod on the passenger size was busted too, so I'll need to get that off (kinda nervous of breaking something; this rack is nice). Would be curious of additional thoughts, though:

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The pump is an LF-30. I'm definitely missing some odds and ends and will assemble those as I have time. Not sure how long this project will take as free time as at a premium right now, but I will keep the updates and pics coming as I make progress!
 
Congratulations on the birth of your first child! Getting a functioning, but basic system, will take about 8 hours. I spent more time on the cooling system for the rack than on any other component. The intermediate shaft can be converted to fit at a lower cost than buying one from a Z4M. The only downside is that fuel consumption will increase by about 3mpg. Good luck and keep us updated.
 
raymond.harper said:
Congratulations on the birth of your first child! Getting a functioning, but basic system, will take about 8 hours. I spent more time on the cooling system for the rack than on any other component. The intermediate shaft can be converted to fit at a lower cost than buying one from a Z4M. The only downside is that fuel consumption will increase by about 3mpg. Good luck and keep us updated.
Click to expand...
Thank you! I’ll keep everybody updated. I’ll have to check out your thread for what you did for the cooling loop. I didn’t bother taking it from the donor car because I read the e46 cooling loop doesn’t fit the Z4. I’m sure I’m missing some other odds and ends as well. It was so damn hot yesterday that as soon as I got the big components off I decided to call it and get out of the heat.
 
Started tearing into the car today. I made a mock-up of the system which details the power steering cooler layout I'm going to use. Here's a photo and video walkthrough:





-Note: I had to get an aftermarket banjo fitting for the bottom port because I forgot to take the original bolt with me from the wrecking yard. Doh.

Took off the front bumper cover:



Here's the stock rack. I first busted the tie rod bolts loose with an 18mm impact.



Then I unbolted the steering shaft from the rack. It uses an E10 bolt on both the column-side and rack-side yokes:




Once that's finished, undo the two 15mm bolts with 17mm nuts that hold the rack on, and pull it free:



Also, I wanted to make a video that explains why you can't use the Z4 shaft with an E46 rack, and how to adapt it for cheaper than a Z4M shaft. Note: I do not take credit for this idea; I read it somewhere else on the forum. I may try buying an E46 intermediate shaft from a 325/330 since they're half the price of a Z4 intermediate shaft ($60 vs 120). I believe the steering shaft yoke is the same and would work on the Z4 shaft.

 
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Hi everybody. A few more updates. I've installed the power steering cooler, pump, and reservoir. I bought an E46 intermediate shaft on ebay for $38 for the yoke. I tried to salvage the u-joint out of it so I wouldn't have to wait on a new one from China, but all I managed to do was damage the caps, so waiting for the boat. Also waiting on front suspension refresh kit (which should come today) that has the inner and outer tie rods. Hoping to get all that installed tomorrow.

Installed location of the cooler:


Reservoir mounts to the bosses already located on the oil filter housing:


After removing the idler pulley, the LF30 pump bolts right in. If you go this way, make sure you get both the front and rear brackets:



I also toyed with using the E46 intermediate shaft, but it's not long enough. Here's a size comparison:


A few videos of my struggles:



Will be back with more updates tomorrow!
 
Okay, an actually serious update. I have the system basically completely installed now. What I have left to do is put the new belt on, reassemble everything that's attached to the column (column is bolted back in), program out the EPS light, and then fill it up with ATF and see if it works. A few step by step notes of the process follow.

I got the steering column out, but had to remove the electric power steering motor while the column was down to be able to snake it out. I think the LHD cars have an easier time with this because there's a lot more room to swing the EPS motor around on the inside of the car, which is where the EPS motor for an LHD car would be. Originally I had planned to remove the motor's shaft and put it back in, but after feeling out heavy it was I decided to ditch the entire motor and have a go at reprogramming (haven't gotten there yet). Here's a short video I shot:



My 1540 ujoint for the intermediate shaft finally came, and I was able to get the intermediate shaft ready to install on the car (sorry, forgot to take a pic of the whole shaft). I went to put it on the car and then hit another roadblock: the intermediate shaft, when fully extended, would not seat far enough on the steering rack splined shaft to clear the milled out part of the shaft where the bolt goes through. It was REALLLY close, but just not quite there. I was scratching my head on this one, but it turns on an E46 yoke is 5mm shorter than the Z4 yoke, so those who bought an extra Z4 shaft for the yoke would not have this issue. Here is the E46 yoke lined up with original Z4 yoke:



Here's a pic of the the issue with it installed. You can see there is a small bit of the upper part of the steering rack splined shaft still sitting where the bolt needs to go through. My solution was to use a carbide bit on my dremel to remove the tiniest amount of metal from the splined shaft to get the bolt through. I also ran a tap through it to make sure the bolt would go the whole way through (FYI, the bolt is M8x1.25):



So the lesson here is the E46 yoke WILL work, but you will need to remove a little bit of material from the steering rack's splined shaft. I went with the E46 because an E46 intermediate shaft was $40 vs. a Z4 at $150.

Here is a video walkthrough of where I am (filmed before u joint came):

 
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10Terp said:
Okay, an actually serious update. I have the system basically completely installed now. What I have left to do is put the new belt on, reassemble everything that's attached to the column (column is bolted back in), program out the EPS light, and then fill it up with ATF and see if it works. A few step by step notes of the process follow.

I got the steering column out, but had to remove the electric power steering motor while the column was down to be able to snake it out. I think the LHD cars have an easier time with this because there's a lot more room to swing the EPS motor around on the inside of the car, which is where the EPS motor for an LHD car would be. Originally I had planned to remove the motor's shaft and put it back in, but after feeling out heavy it was I decided to ditch the entire motor and have a go at reprogramming (haven't gotten there yet). Here's a short video I shot:



My 1540 ujoint for the intermediate shaft finally came, and I was able to get the intermediate shaft ready to install on the car (sorry, forgot to take a pic of the whole shaft). I went to put it on the car and then hit another roadblock: the intermediate shaft, when fully extended, would not seat far enough on the steering rack splined shaft to clear the milled out part of the shaft where the bolt goes through. It was REALLLY close, but just not quite there. I was scratching my head on this one, but it turns on an E46 yoke is 5mm shorter than the Z4 yoke, so those who bought an extra Z4 shaft for the yoke would not have this issue. Here is the E46 yoke lined up with original Z4 yoke:



Here's a pic of the the issue with it installed. You can see there is a small bit of the upper part of the steering rack splined shaft still sitting where the bolt needs to go through. My solution was to use a carbide bit on my dremel to remove the tiniest amount of metal from the splined shaft to get the bolt through. I also ran a tap through it to make sure the bolt would go the whole way through (FYI, the bolt is M8x1.25):



So the lesson here is the E46 yoke WILL work, but you will need to remove a little bit of material from the steering rack's splined shaft. I went with the E46 because an E46 intermediate shaft was $40 vs. a Z4 at $150.

Here is a video walkthrough of where I am (filmed before u joint came):

Click to expand...


Hi, sorry, I'm trying to get me head around the issue here and I think I've gotten myself confused.

Is the solution to fit the E46 lower yoke to the Z4 shaft? Or is it to use the E46 shaft?

It was this line that confused me "so those who bought an extra Z4 shaft for the yoke would not have this issue" followed by this line further down the page "So the lesson here is the E46 yoke WILL work,"

Many thanks
 
Actually, I think I've got my head around it.

Instead of using the lower yoke from an E46 mated to the bottom of a Z4 shaft, it's better to use the upper yoke from a Z4 shaft mated to the bottom of a Z4 shaft.

Is that correct?
 
damocell said:
Actually, I think I've got my head around it.

Instead of using the lower yoke from an E46 mated to the bottom of a Z4 shaft, it's better to use the upper yoke from a Z4 shaft mated to the bottom of a Z4 shaft.

Is that correct?
Click to expand...
Hi, I’m sorry I missed this message. Just getting back to the project after life getting in the way for a while.

You’ve got it correct. You will need another yoke from the steering column side of another z4 steering shaft to fit to the power steering rack end of the steering shaft. An e46 steering column yoke works too (which what I originally tried), but I wouldn’t recommend it as the steering shaft will be at full extension and you’ll need to trim a little bit of metal off the steering rack splined shaft to get the bolt through. I hope this helps.

Managed to figure out how to code out the EPS light today using a copy of INPA/NCS Expert I found on bimmerforums. Time to do some shakedown runs to make sure everything is working as it should.

This guide got me 95% of the way there:

NCS Expert Codieranleitung für BMW Fahrzeuge

Hier habe ich eine Anleitung erstellt mit der BMW Fahrzeuge codiert werden können. Die Codierung des BMW's erfolgt mit dem Tool NCS Expert (NCS Expertentool). Für Fragen und Hilfe bitte im unteren Bereich einen Kommentar verfassen.
www.oliverhaas.net
 
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10Terp said:
Hi, I’m sorry I missed this message. Just getting back to the project after life getting in the way for a while.

You’ve got it correct. You will need another yoke from the steering column side of another z4 steering shaft to fit to the power steering rack end of the steering shaft. An e46 steering column yoke works too (which what I originally tried), but I wouldn’t recommend it as the steering shaft will be at full extension and you’ll need to trim a little bit of metal off the steering rack splined shaft to get the bolt through. I hope this helps.

Managed to figure out how to code out the EPS light today using a copy of INPA/NCS Expert I found on bimmerforums. Time to do some shakedown runs to make sure everything is working as it should.

This guide got me 95% of the way there:

NCS Expert Codieranleitung für BMW Fahrzeuge

Hier habe ich eine Anleitung erstellt mit der BMW Fahrzeuge codiert werden können. Die Codierung des BMW's erfolgt mit dem Tool NCS Expert (NCS Expertentool). Für Fragen und Hilfe bitte im unteren Bereich einen Kommentar verfassen.
www.oliverhaas.net
Click to expand...

Thanks that helps. I’d started on creating one from two S4 shafts but then a Z4M one came up for a steal so I bought that instead.

I know have a Z4M, 1 full Z4 and one with a yoke removed 🤦🏽‍♂️
 
Took the car for a test drive finally, and something isn't right with the PS system. A few issues:
  1. The steering will not return to center after turning. It basically locks in place and you have to steer it back to center. My understanding is this is typically a caster issue, but the caster on our cars (I think) is not adjustable. I did also replace the lower control arms and outer tie rod ends and did an eyeball alignment, so I supposed it could still be alignment issue (it pulls hard to the left on driving).
  2. The steering still feels quite heavy. My first suspicion was a tight strut, so I got the front wheels off the ground and disconnected the tie rods and swaybar links on each side - both struts rotate fine and don't feel excessively tight. I did notice the struts seems to change angle slightly as you rotate them. For example, if I swatch the top part of the strut from the wheel well while rotating it, the angle changes slightly and the rubber on the upper strut mount bends a tad. Also, with the car started up turning the wheel with tie rods disconnected is still quite heavy. I believe I have a yellow tag rack which is supposed to be heavier, but it seems almost too heavy.
  3. Steering angle sensor lights. I stupidly threw away my EPS motor, which I'm kicking myself in the head for. Now I've got DSC and a yellow brake light on that won't go away. Using my Creator C310+ it shows me the lack of communication from the steering angle sensor is the culprit.
Certainly open to feedback on any of these!
 
I'm not sure about your other issues, but the HPAS in my Z4M is significantly heavier than the EPAS in my previous 3.0Si.

My E90 330i also has HPAS and that is also a fair bit heavier than the 3.0Si EPAS, but both HPAS set ups give much better feel than the EPAS did.
 
Deleted my comment as it was obviously rubbish and don’t want to misinform the OP. My apologies.
 
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Thanks, yeah it was a bone headed move of me to get rid of it. I may just code out the lights to get it through safety inspection then try to figure out a better solution.

Regarding the heavy steering, I just took the banjo bolt off with the check valve in it and yanked the check valve out. No change in steering effort. Then I shut the car off and the steering effort felt exactly the same as with the car running. Also, when I had the banjo fitting out the entire reservoir drained through the pressure hose, which means fluid is freely flowing through the pump when the car is off (not sure if this is normal?). Either way, something isn't right.
 
enuff_zed said:
Can't help much, but the Steering Angle Sensor is connected to the EPS motor ECU, so if you threw the whole thing away then there is nothing for it to connect to and feed back it's readings. As mentioned by someone else, you need to retain at least the ECU. I think I would be tempted to refit the whole motor but with the worm drive cut off.
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1. The steering angle sensor sits on the lower side if steering column, nothing to do with EPS.
2. The steering angle sensor connects it's signal through D-can and not to EPS so event if you disconnect the EPS it will still have signal. Mostly the OP have to re-calibrate the angle
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