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Theres quite a lot on here regarding the Power steering
1. Servotronic valve going kaputt.
2. BCU
3. PAS pump
from https://www.fullfatrr.com/forum/topic46079...r+steering
causes of heavy steering :
The heavy steering evolved after 6 months or so of non-action from an intermittent problem into a permanent problem.
Steering effort when stationary or at low speed was really heavy - to the point I gave up manoeuvring in car parks occasionally & left the car across 2 parking places. The only way to gain steering assistance at slow speed was to try & use the throttle to "blip" the engine speed.
After using a digital voltmeter on the electrical connections in between the BCU & steering rack Servotronic valve, I confirmed that the valve & the BCU were working OK - also wasted £100 replacing a fully functional Servotronic valve & £60 on a secondhand (temporary) replacement for our original BCU.
For info BCU voltage output to the Servotronic varies from around 7.5 volts stationary down to 2.5 volts at speed.
PAS fluid was changed together with a reservoir clean out with no effect on the heavy steering.
Hoses were all checked over for damage, swelling or any other defects - again with nothing found.
As a temporary minor improvement, I by-passed the BCU output & applied 12v direct to the servotronic valve - however, the improvement was only while moving at low - medium speed (ie when the effect of the servotronic valve would normally reduce).
Eventually - wary of a probable MOT failure - I decided to "bite the bullet" & create some pressure test equipment to check the pump performance by connecting between the PAS pump HP output & the HP pipe banjo.
LR specify test kit in the Workshop Manual, but I couldn't find anywhere selling anything similar, so ended up creating a kit by buying the individual parts (gauge, fittings, a couple of hoses & a HP shut off valve). I also bought a cheap S/H OE PAS pump to check the pipe connections before working on the car.
Use of the kit requires removal of the airbox, draining the PAS reservoir to permit removal of the PAS pump HP banjo connection & installation of the test kit connections.
Results of the test were significant !
The Pump should deliver more than 100bar at idle when the steering wheel is turned. I was only getting 20~ 30 bar - totally explaining the heavy steering / lack of assistance !
The pump output only climbed to 90bar at nearly 3000 rpm - also explaining why blipping the throttle / holding higher engine rpm would generate some assistance.
The pressure kit was then removed while I considered whether PAS pump replacement was an acceptable DIY job on the drive.
After more forum searching & discussion with j_rov, a local friend & forum member who'd had the unfortunate "pleasure" of changing his complete 3.6 TDV8 engine due to it digesting a broken EGR valve, the decision was that it was doable, but probably painful due to the rear pump retaining bolt not being easily accessible.
Forum comments also suggested that my second hand pump was probably OK - unless I was very unlucky - as internal failure was not very common across the many different vehicle applications using the same base ZF pump (Land Rover, VW Audi, Porsche, BMW etc).
Last week, with a good weather forecast, I tackled the pump removal & replacement (documented elsewhere as a new "How to "). I took much longer than the 3 hours suggested by 1 of the few people online I'd seen who'd tackled it as a DIY job Total time was 7 hours, but I was working very slowly due to the excess heat & excess tea breaks !
However, the result was great - I'd re-gained assistance at idle / stationary & the steering felt as the few good vehicles I'd driven (I'd bought the car with a known partial problem).
As side bonus', the engine appears slightly quieter / more refined - which I think maybe due to a few exhaust shield mounting studs I found without retaining nuts & sorted while doing the job.
Problem solved !
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2nd Apr 2020 5:15pm
