I think that you've demonstrated that the servotronic valve is OK.

Power assistance occurs when the torque rods that connect the input shaft to the pinion flex under the load when trying to turn the pinion to the point where an oilway opens allowing pressurised oil to be sent to the ram in the rack. As the rack starts to move in the direction of turn, the torque rods start to return to their unloaded shape thus closing-off the oilway to the ram, reducing/removing power assistance. The more the wheel has to be turned before assistance starts, the heavier the steering will be because more of the effort to move the rack will be provided by the wheel/driver.

I don't know if the pinion/rack preload adjuster, which is accessible with the rack in-situ, also impacts assistance.

Okay so we're saying it's probably not the pipes, the pumps new, the resevoir is new, the cooler no longer leaks and the servotronic valve checks out OK. (We think)

That really only leaves mechanical binding somewhere as mentioned earlier strut top bearings, ball joints or UJ.

Outside of that it's the rack itself but given the age and value of the car it's not worth it to spend the money without a guarantee it will fix the issue.

That's before we even get stuck into the laggy engine/gearbox or the bouncy suspension.

I agree with GraemeS, you've eliminated the Servotronic valve.
The only extra test I did was to apply a direct 12V to it to bypass the BCM effects and confirm that it gave permanent full assistance - regardless of engine & vehicle speed.
However, I think you've done the equivalent via your use of SDD.

I think you're only left with mechanical effects - which I don't remember you investigating via any of the comments I've read.
I think you need to jack the car up & test the steering without the engine running to see if there is some form of mechanical resistance influencing the steering effort.

As a PS I think you've eliminated the PAS pump via changing it, but have you tried the "test" where you start the engine, apply some minor steering lock & then while holding the steering wheel still, increase the engine revs. Its quick and simple.
If the PAS pump and hydraulic system is working OK, you shouldn't feel anything via the steering wheel as PAS pressure should already be at maximum with the engine at idle.
If the steering wheel tries to rotate further or the effort to hold it reduces - indicating that the PAS assistance has increased due to the increased engine speed (ie pressure has increased), it indicates a problem with the pump output a idle. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Afternoon Pawl,

Glad we agree re servotronic, I haven't done the direct 12v test no but I did use SDD as you say to force the valve to max assistance mode and not much difference was noted.

Something I find interesting though is when viewing the signal/voltage to the valve in SDD or using the Autel it reads 0v as if nothing is being sent?

I will try turning the steering with the wheels off the ground and engine off to see if I can notice any binding.

I have tried the test you describe in taking up the slack in the steering then bringing up the engine RPM (about 3k rpm) but the wheel does not move as you describe so that would suggest that the new pump is already giving its best and can't produce any more pressure correct?

Graeme, I just read your post via search regards your steering becoming heavy post input seal replacement.

Did you manage to figure it out?

Yes, grit had found its way into the pump and caused the valve piston to stick open thus providing almost no pressure. Once freed, power assist was working again.

Excellent result Graeme, well done that man

I'm going to try and get this car of mine in the air today to see what the steering is like lock to lock wheels off the ground.

Thank you to both you and Pawl for putting up with my moaning and continuing to try and help me.

Hopefully one day I'll get it all figured out and have an RR that drives as it should!

Okay, so I've had it up in the air today to check for binding.

Turning the wheel lock to lock with the engine off, there is resistance like how Graeme described, the resistance increases as the steering approaches its extremity at the end of the racks travel. (I.e the lock)

Turning the wheel lock to lock with the engine running is nice and easy.

Here's a video showing that: ?si=VGfcY_3tax7GyLBM

And a video showing the fluid in the reservoir with the engine running:
https://youtube.com/shorts/FXKRT8JF7gg?si=PYJToK4dI4USaRVx

I have a little bit more to add.

Thought I'd have another play in SDD to show you what I meant regards voltage output to the servotronic valve.

Here's what is shown when selecting the servotronic related data pids(?) Underneath the 'suspension' heading:



And the same again but under the 'body system' heading:



As you can see in the first it says 0 volts and in the second it just gives an error.

This is also what the Autel says. 0v.

I though this may be an error in my copy of SDD but it shows the steering angle sensor value just fine and this changes as I turn the wheel.

I then thought I'd try forcing the valve to max via the data logger function again, steering did not get lighter.

So I then had the idea to force it to minimum expecting the steering to get heavier but it did not, it remained the same weight in both tests!

I figured maybe the functions aren't actually working so found a PID for central locking and one for the drivers window and nope they don't work either.

Basically what I am trying to communicate is my earlier test in this thread of forcing the valve to maximum (I.e lightest steering possible) wasn't actually going anything.

I think the "error" might be because the BCM outputs a PWM (Pulse Width Modulation) signal - effectively pulses of voltage to drive the Servotronic valve. The gaps between the pulses reduces as the vehicle speed reduces, so that the valve opens more. 12v is being applied - but not continuously.

I tried measuring it with a digital voltmeter while driving and it would only show as a low voltage of about 5V max.
When I found out a bit more about PWM signals I was told you need very fast (ie expensive) data logging equipment to see what's happening - eg an oscilloscope - as most voltmeters don't sample the signal at a high enough frequency to see the full signal.
I can't imagine the SDD has got a really fast sampling rate.

I did a very simple test of connecting a positive and negative battery feed directly to the Servotronic connector pins to get max opening / assistance.
The effect (steering effort) was exactly the same as the BCM output at low vehicle speed. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

I completely understand what your saying Pawl regards measuring PWM (continous on/off pulse) signals but it seems a bit redundant for LR to include this data PID in the software if its unable to read anything.

I'm also sure I've viewed this before on previous L322s.

Anywho I definitely need to try the direct 12v test as I think I've proven my copy of SDD isn't able to control the output to the valve (although again I'm sure I've done this on previous L322s but I do have the software on a different laptop now)

I'll try to rig up a connector so as to avoid having to chop the one on the car off the loom and solder back in.

With the connector unplugged from the valve and with the engine running but the vehicle not moving, is the steering quite a lot heavier than with the connector fitted? However, I think that you've already tried this and found the steering ligher when connected.

Well today has been a very strange day indeed...

Whilst I was out messing around in SDD last night it was snowing outside and around 0 degrees.

Woke up this morning to a small smattering of snow on the houses, cars and greenery but nothing on the road.

Decided to take the Range Rover for my commute just in case and strangely the steering was considerably lighter but also the engine felt great, full power and no lag/hesitation, no revs dropping to idle whilst coasting off accelerator etc.

Then the strangest one (bearing in mind this car doesn't have adaptive suspension) the ride was better and more compliant.

It's still bouncy but it was soft and bouncy.

I really enjoyed today's commute, felt like a totally different car!

I left work expecting it to have fluked like my previous RRs but no it drove exactly as it did this morning!

I was able to 'palm' the wheel whilst maneuvering around our cul-de-sac.

Very dark video below:
https://youtube.com/shorts/oshA8K6E7UI?si=WKGQXBtYvYG96jYk

I have no idea what it is I did last night but today the L322 has almost felt 'right'

amazing RR 2005 4.4 petrol
Any spelling mistakes are the fault of spellchecker
Previous MG J2, CITROEN light 15 x 2 gone unfortunately
Present MERC 180e, RANGE ROVER L322, JAGUAR XJS, MERC 280SE, MG F, JAGUAR S-Type 6v 2003, jaguar s-type 8v 2004, Ford Cougar

Still driving okay today