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Hydraulic steering conversion - N52-engined Z4 models

2003 - 2009, roadster, coupe, facelift
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Hydro_Z4
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Hydraulic steering conversion - N52-engined Z4 models

Post by Hydro_Z4 » Tue Oct 29, 2019 12:32 pm

As I've used this forum as a source information for quite a while it only seemed fair to give back where I can.

Credits go to Ray Harper's excellent thread for RHD M54 cars as reference:
viewtopic.php?f=2&t=92858

This guide applies to all N52-engined Z4 models:
2.5i Roadster (facelift only)
2.5si Roadster
3.0i Roadster (facelift only)
3.0Si Roadster
3.0Si Coupe

There are some slight differences in parts required between left-hand drive (LHD) and right-hand drive (RHD). These are marked in the text below. For those who may not be familiar with the terminology... LHD applies to vehicles from Europe, North America, etc. RHD applies to vehicles from UK, Australia, Japan, New Zealand, South Africa, etc

This guide should map quite well to M54-engined cars, with adjustments to take into account LF-20 instead of LF-30 steering pump. This should be limited to high-pressure line from pump to rack (specific to LF-20 steering pump - there are LHD and RHD versions), V-belt 6PK 1538 (11287636379) and mounting screw M8x22 (07119905739). There is a M54 mounting bracket for the reservoir (32411092940) with screw (7119904524) and 2x screw (7119905529).

Note that all steps in this conversion are in principle reversible. That means the car can be reverted to original condition if required in the future.


================== Disclaimer ====================

The steps in this thread are very much to be done at your own risk.

Technically this conversion is not highly complex to execute. However as the steering system is a safety-related function it is not be undertaken lightly.

In your geographical area, the conversion may need to be declared to insurance and/or local authorities. This is something you will need to check yourself before proceeding.


================ EPS adjustment ===================

Note that hydraulic steering conversion may not be desirable or suitable for many Z4 owners.

I would very much recommend adjusting EPS before considering hydraulic steering conversion.
viewtopic.php?f=3&t=100725


================== Motivation =====================

My reasoning for this conversion. Basically, I wanted to achieve more accurate and linear steering feel.

On bumpy or uneven roads EPS made the car feel twitchy and on faster roads it tended to tramline or wander a bit. Also, as my car is occasionally used on racetracks, EPS continuously wanted to assist and adjust mid-corner making steering feel rubbery at best. As I'd taken all slack out of the car with new bushings and suspension it was quite obvious EPS was the issue that I needed to address.


=================== Parts List =====================

Intermediate Shaft
Z4M Intermediate Shaft (LHD) (32307836809)
Z4M Intermediate Shaft (RHD) (32307836811)
Almost impossible to find used. Basically consists of Z4 upper shaft paired with E46 lower shaft. For a workshop with access to the correct tools, it should be possible to inexpensively produce the intermediate shaft from used parts. That may be worth considering should BMW parts supply become exhausted in the future.
Purchased new from BMW

Steering rack
Basically a variety of BMW hydraulic steering racks could be used. However, a steering rack with a short gear ratio is preferable as it makes the vehicle feel livelier. A selection of steering racks and ratios: E46 15.4 / E46 facelift 13.7 / E46 M3 15.4 / E46 M3 CSL 14.5 / E85 Z4MR 13.7 / E86 Z4MC 12.8
For comparison - the ratio of the standard E85 / E86 steering rack should be 14.2.

By far the cheapest variant is the steering rack from the E46 facelift with a ratio of 13.7 - either a 'yellow tag' (7852974712(LHD)) or 'purple tag' (7852974678(LHD), 7852974679(RHD)). The yellow tag rack is rumoured to have been produced for US-market 330i ZHP with slightly heavier duty internals. However I found these racks advertised in salvage yards in Europe originating from a wide variety of E46 models.

Hoses (LHD)
The hoses are found on any LHD 6-cylinder petrol E46 variant - 320i, 325i or 328i. Salvage yards will often throw these parts in for free with a used steering rack. Be careful not to lose green O-ring in the high pressure line connector!
Required parts
Line from reservoir to pump (32416750155, part 1 in diagram)
High-pressure line from pump to rack (32416774215, part 3 in diagram) - specific to LF-30 steering pump
Line from rack to cooler (32416796367, part 7 in diagram)
Cooler return line (32416796390, part 11 in diagram)
Additionally source:
Cooling loop (17111436262, part 10 in diagram) (any E46)
Reservoir (32416851217, at top of diagram) (any modern BMW)
For reference diagram of parts:
Preparation1.jpg
Preparation1.jpg (68.24 KiB) Viewed 8164 times
Hoses (RHD)
The hoses are found on any RHD 6-cylinder petrol E46 variant - 320i, 325i or 328i. Salvage yards will often throw these parts in for free with a used steering rack. Be careful not to lose green O-ring in the high pressure line connector!
Required parts
Line from reservoir to pump (32411095526, part 1 in diagram)
High-pressure line from pump to rack (32416764728, part 3 in diagram) - specific to LF-30 steering pump
Line from rack to cooler (32416774214, part 4 in diagram)
Cooler return line (32416796390, part 14 in diagram)
Additionally source:
Cooling loop (17111436262, part 13 in diagram) (any E46)
Reservoir (32416851217, at top of diagram) (any modern BMW)
For reference diagram of parts:
Preparation1 - RHD.jpg
Preparation1 - RHD.jpg (66 KiB) Viewed 8038 times
Pump
The steering pump is found on N52-engined E90 variants - 323i, 325i or 330i. Ensure the pump includes pulley and rear mounting bracket.
LUK LF30 pump (32416769887)
For reference image of pump with attached bracket:
Preparation2.jpg
Preparation2.jpg (38.39 KiB) Viewed 8164 times
Miscellaneous
You'll require various parts which are cheap and easy to source new from BMW.
Reservoir mounting bracket (32416768096) - (could be sourced from any E90)
Screwset power steering pump (32420392609)
Pulley (11287535860)
V-belt 6PK 1990 (11287628650)
Blind rivet (51718219511) 6x (for remounting front bumper)


================== Preparation =====================

Prepare beforehand by spraying WD40 liberally on tierods of hydraulic steering rack.

To reduce installation time, the mounting bracket for the reservoir could be fabricated beforehand.


=================== Conversion ====================

The installation work was performed at my trusted BMW mechanic. Having a lift really helps.
Total installation time - including fabricating reservoir mounting bracket and tracking - circa 8 hours.


============== Step 1 - installing hydraulic steering rack ========

Remove under engine compartment covers as well as aluminum reinforcement plate
Disconnect tierods, disconnect intermediate shaft and mounting bolts for steering rack.
Remove steering rack. Remove intermediate shaft.

Install Z4M intermediate shaft, install hydraulic steering rack, connect tierods.


============== Step 2 - removing EPS motor ===============

Remove under-dash paneling.
Remove 2 bolts holding EPS motor and wrestle it out.
Disconnect wiring.
Re-install under-dash paneling.

For driveway mechanics... you theoretically (after wheel alignment) have a drive-able car again albeit with quite heavy steering.


============ Step 3 - installing hydraulic pump ==============

Loosen tensioner for V-belt, remove V-belt.
Unused mounting holes for the LF30 hydraulic pump are present on the engine block. Run a thread tap through the mounting holes as they are likely dirty and oxidized. Install hydraulic pump using new bolts (see set above).
Install additional pulley on alternator - pulley set comes with bolt and dust cap.
Install new V-belt and tighten tensioner.
Install high-pressure hose from pump to rack.

For reference routing of new V-belt over pump and new pulley:
Step3.jpg
Step3.jpg (34.7 KiB) Viewed 8164 times

============= Step 4 - installing cooling loop ===============

Remove front bumper. Provisionally install cooling loop, you'll need to cut away some plastic beside the radiator to route hoses.
Install hose from rack to cooling loop.
Provisionally install hose from cooling loop to reservoir.
Interestingly, the right-hand radiator support on all Z4 bodyshells stems from the E46 and already contains the mounting tab for the cooling loop, just much higher than required. Cut mounting tab loose, mount on cooling loop with ziptie and screw/glue in place in the correct location on radiator support.

Alternatively, the mounting tab could be left in the higher original location. This will require adjustments to length of hoses to cooling loop, additionally radiator hoses may be in the way.

For reference mounting tab for cooling loop:
Step4.jpg
Step4.jpg (91.66 KiB) Viewed 8164 times

============== Step 5 - installing reservoir ================

Next a place will need to be found to mount the reservoir. Ideally it's located higher than the pump however available space in the left front of the engine bay is limited. A suitable location is located on the lower schock tower, additionally at this exact point there are also 2 unused welded nuts on the shock tower itself.

Start by removing the air filter housing to obtain access. Here various N52-engined Z4 models differ. Airbox shape and intake ducting vary, also some models have sound generator and associated ducting.

(From what can be seen in the parts manual, there should be sufficient space for the reservoir if there is no sound generator.)

For our 3.0Si we chose to modify part of the sound generator, where there is a fist-sized resonator chamber sticking downwards. This was cut off and ground down leaving a round hole which was capped off. By doing this space was created next to the lower shock tower.
For reference sound generator modification:
Step5.jpg
Step5.jpg (64.3 KiB) Viewed 8164 times
(Alternatively, an option for models with sound generator may be to install aftermarket open air filter which opens up space for the reservoir further forward in the engine compartment)

A mounting bracket was fabricated to fix the reservoir to the shock tower. The reservoir was attached to the bracket using the stock E90 reservoir mount.
Step52.jpg
Step52.jpg (81.54 KiB) Viewed 8164 times
Install hose from pump to reservoir. The hose from cooling loop to reservoir is the only one that requires modification. Either use an additional spare E46 hose or cut hose and lengthen with piece of metal tubing and hose clamps.


================== Step 6 - tidying up =================

Fill hydraulic system with red hydraulic fluid as used in BMW E46 models.

Start engine. Turn steering from lock to lock to remove air bubbles. Check hose connectors for leaks. Top up reservoir if required.

Re-install air filter housing.

Re-install front bumper (you'll require new blind rivets in the wheel wells).

Re-install aluminum reinforcement plate and under engine compartment covers.


============== Step 7 - wheel alignment =================

Perform wheel alignment.


============== Step 8 - EPS warning light =================

After removing the EPS motor, the EPS warning light will be permanently illuminated on the instrument cluster.
Step8.jpg
Step8.jpg (49.03 KiB) Viewed 8164 times
There are various options to address this.
1 - open instrument cluster and cover the EPS warning light
2 - remove axle from EPS motor and reinstall on steering column
3 - recode software to ignore lack of EPS motor

With options 1 and 2, the modification is not easily reversible.
Option 3 is a proper solution.

The following webpage was quite helpful in determining what needed to be done.
http://www.oliverhaas.net/thema/ncs-exp ... zeuge.html
http://www.oliverhaas.net/bmw/bmw-steuergerat-akmb.html

To switch off the EPS warning light you'll require access to a laptop with BMW INPA software. There are numerous technicians with this software package - start by asking on this forum or your local BMW specialist. Within the INPA software package is a tool called NCS Expert for reading, troubleshooting and recoding BMW ECU's.

The EPS warning light is controlled by one of the main ECU's in the E85 Z4 - the AKMB ECU. As the AKMB ECU is universal to various Z4 variants - the presence of optional systems such as automatic gearbox, convertible roof, regional acoustic warnings and EPS can be configured.

Using NCS Expert the parameter settings of the AKMB ECU can be modified. To disable EPS warning light, the parameter 'EPS' needs to be changed from 'aktiv' to 'nicht_aktiv'.
Step82.jpg
Step82.jpg (121.3 KiB) Viewed 8164 times
For someone experienced with BMW INPA software, the above procedure will only take a few minutes. This step is straightforward and remuneration should not be more than order of magnitude of a crate of beer. After switching ignition off and on, the EPS warning light is disabled permanently. As mentioned earlier, this step is easily reversible in case EPS is reinstalled in the future.
Step84.jpg
Step84.jpg (45.56 KiB) Viewed 8164 times

============== Step 9 - Legalities ======================

In your geographical area, the conversion may need to be declared to insurance and/or local authorities.
This is something you will need to check yourself.
Last edited by Hydro_Z4 on Sun Jul 16, 2023 10:50 am, edited 8 times in total.

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DOOM
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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by DOOM » Tue Oct 29, 2019 2:27 pm

simply a m a z i n g content.
bravo.
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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by Ag51bye » Tue Oct 29, 2019 3:29 pm

I’ve been eyeing up pumps and belts that I thought may work.

Your post has taken all the guess work out - for that I thank you.

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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by QUIKSTER » Tue Oct 29, 2019 3:37 pm

As for the non-techie hands on people like myself as said before, I would be interested to know on costs if this conversion was available as drop in and out service.

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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by Capa » Tue Oct 29, 2019 6:06 pm

Roll in roll out is about 2k from Ergan Motorsport, from what I recall.

Good content, nonetheless.
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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by DaveD » Tue Oct 29, 2019 10:16 pm

Great job OP. This is one mod I’m really interested in.

Now you’ve installed it, what is your view of the improvement to the twitchy steering and vague feel that I too have on the eps rack? Has it made the car easier to pilot down bumpy roads without that wandering feel? I’m in a similar boat to you in that I’ve done all the bushes etc and it’s much better as a result, but still not as I want it ideally. Less feedback from bumps and cambers would make Cross country pace more accessible.
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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by Mr Tidy » Tue Oct 29, 2019 11:26 pm

That is a fantastic "How To" OP. :thumbsup:

I just wish I had the skills (and a suitable place) to do this - the Hydraulic PAS on my E90 3 Series is just so much better.

No wandering, no tramlining and so much more feel - I just don't know how much of that is due to the HPAS, or maybe because it's a different car?

Tempting as it is to think about getting it done £2K isn't cheap - factor in a Quaife at £1.4K and it would make more sense to look for an MC. :lol:
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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by Hydro_Z4 » Wed Oct 30, 2019 7:11 am

Mr Tidy wrote: Tue Oct 29, 2019 11:26 pm I just wish I had the skills (and a suitable place) to do this - the Hydraulic PAS on my E90 3 Series is just so much better.
We have an E90 as daily driver as well. It's excellent compared to E85 EPAS.
Mr Tidy wrote: Tue Oct 29, 2019 11:26 pm No wandering, no tramlining and so much more feel - I just don't know how much of that is due to the HPAS, or maybe because it's a different car?
That's exactly what this conversion achieved.

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Hydraulic steering conversion - LHD N52-engined Z4 models

Post by Hydro_Z4 » Wed Oct 30, 2019 7:56 am

Now added RHD specific parts as well

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Hydraulic steering conversion - N52-engined Z4 models

Post by mjennings23 » Wed Oct 30, 2019 11:23 am

Top write up, albeit not relevant to my car I'd still like to show my appreciation!

Regarding disabling the EPS in NCSExpert, I assume you still maintain operation of the 'sport' mode button? Probably much more relevant to those with an auto as it sharpens up the gear changes as well as the throttle response.

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Hydraulic steering conversion - N52-engined Z4 models

Post by Hydro_Z4 » Wed Oct 30, 2019 11:43 am

mjennings23 wrote: Wed Oct 30, 2019 11:23 am Regarding disabling the EPS in NCSExpert, I assume you still maintain operation of the 'sport' mode button? Probably much more relevant to those with an auto as it sharpens up the gear changes as well as the throttle response.
Thanks. Hope it answers most questions that were keeping people from performing the conversion - myself included.

The E85/E86 platform deserves decent steering feel - it's a fun sportscar that's been handicapped by some unfortunate technical decisions late in the development process.

Sport mode is disabled as one of the key components (EPS) is missing. Not relevant (IMHO) for manual cars, however definitely relevant consideration for auto cars. For those cars the way to go would be to remove the EPS axle and remount the EPS motor.

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Hydraulic steering conversion - N52-engined Z4 models

Post by Darkangelv2 » Wed Oct 30, 2019 3:10 pm

Superb. I will now start trying to accumulate parts! :thumbsup:

THANK YOU!
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Hydraulic steering conversion - N52-engined Z4 models

Post by xZZZZx » Sun Sep 27, 2020 1:34 am

Hydro_Z4 wrote: Wed Oct 30, 2019 11:43 am Sport mode is disabled as one of the key components (EPS) is missing. Not relevant (IMHO) for manual cars, however definitely relevant consideration for auto cars. For those cars the way to go would be to remove the EPS axle and remount the EPS motor.
Great post hydro! I'm now starting to source parts.

But can you give any further details on how to remount the EPS motor? I can't quite get my head around it.

Nice one :thumbsup:

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Hydraulic steering conversion - N52-engined Z4 models

Post by rosskins » Sun Sep 27, 2020 10:09 pm

Just wow. I loved the feeling and drive of my e46 325ti, just wonder how this will translate into my 3.0si? Brilliant guide! :thumbsup:
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Before: ZR3.0si, 525d, 325ti, 120d, A3-2.0DSG, 323T4x4, MX3-V6, 2CV, MetroVP, Mini850
Zed was fitted with: None run flats, Stubby, Cruise, Intravee, DrilledFogs, WiredCam & 326s

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Hydraulic steering conversion - N52-engined Z4 models

Post by Mr Tidy » Sun Sep 27, 2020 10:32 pm

I'm also a former E46 325ti owner too and I loved how that drove, although the steering always felt pretty heavy to me.

But now I've got an E90 330i with HPAS and it's steering feels even better than the E46 did, and would probably be much like this conversion as it uses mainly E90 parts.
Coupes because stunning!
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Gone - Montego Blue
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