Harsh Vibration full lock

[jpliddy]

hi
please read my threads on this problem i changed rack .power steering pump. second hand of course .still the same problem I'm almost certain it was a air in system . it just clears up one day a few weeks after i had work done . . i changed power steering oil . think that helped to cure it . it was a while ago but bad vibration on lock turning right . keep us informed

[lynns hubby]

Thanks for the replies chaps, It still does it but it is not so bad. You can still feel it but the noise has gone. trouble is it does not Always do it. Just when you think that it was air in the system and its bled itself it does it again!!!!!!

[jpliddy]

hi
on whats been said . I'm still thinking air is in the system . the high pressure hose on mine has had oil mist around the bottom of pipe since i had the car . i used to wipe it now and again . so if a bit of mist /oil getting out air can get in .thats my thoughts only had the problem once but it took time to settle down .coming up to 20 years of ownership on this car now if it pass the next M.O.T in April .

[lynns hubby]

Well its been behaving itself lately, I have not heard it or felt it for the last few weeks so hopefully it was air and it has now finally bled itself.

[bluebrickrick]

Given the wind has had a chance to warm up on its way through Yarmouth and its been B cold here at Bogside, praps the vibration is just the poor old dear shivering as you headed her into the icy blast...................

[lynns hubby]

Well I spoke too soon, its still doing it if you are a bit over zealous with the steering. Manoeuvring in car parks etc if you are quick with the wheel. I changed the pump out for a known good one and it made no difference.
Looking more and more like the rack.

[lynns hubby]

Well in desperation I bought a new rack and changed it. Its still made no difference. It is really pronounced now, as I back out of our drive on full left lock it feels like it is just dragging the front wheels and skipping. Its just passed its MOT with no advisories. I explained the issue to the tester but he said he could find nothing wrong. There is no indication of unusual tyre wear. I have made an appointment to get the tracking checked (after fitting the new rack) and have sought a performance centre that does Laser alignment so will get the castor and camber checked as well.

[tofufi]

I've a similar problem with my 740 - I've not taken a look at it yet as it's only started a day or two ago. Please keep us updated with how you get on

[jpliddy]

this problem is not uncommon i had a similar problem see my posts . i had some serious vibration on a few occasions after my m.o.t.s now thats strange always thought the testers were doing things the old car did not like but after a short while it all settled down . i had my rack replaced too got one from a breakers the steering still vibrated on lock but again its been vibration free for a number of years now . im putting my problem down to air in the system . try and get as much of the old oil out and new oil in . !

[Laird Scooby]

Something to check for before you get the wheel alignment/tracking done is that the rack is centralised so with the steering wheel in the straight ahead position, the rack is dead centre.

It should be 1 3/4 (1.75) turns from the central position of the steering wheel to each lock. If it isn't, you'll have to remove the steering wheel and reposition it so that when the steering wheel is in the straight ahead position, the rack is in the centre of its travel.

The reason for this is that in the central position, the spool valves in the rack (that pass hydraulic fluid from the pump to the rack to give the assistance) are closed. If the rack isn't properly centred, one or other of these valves will be open while driving in the straight ahead position. This can cause the PAS fluid to overheat due to the fact it is being worked that much harder by the rack not being in the "dead" central position.
If it overheats, it can draw air in and cause cavitation in the pump, resulting in aerated fluid. In extreme cases, especially on pumps with an integral reservoir, it can cause the fluid to overflow resulting in low fluid. This exacerbates the problem.

If this is part of your problem, you'll find the steering wheel is probably not in the straight ahead position while driving straight ahead after you've centralised the rack so be careful until you get the tracking adjusted - it's human nature to pull the wheel to the straight ahead position while driving straight.
You'll also notice the self-centring effect is more obvious after getting the tracking done if this is part of the problem.

Finally, if that has been part of your problem, change the fluid afterwards using this method :

With a large syringe (200ml or thereabouts) suck all the fluid out of the reservoir. Top up with fresh, start the engine and bleed the system by slowly turning from lock to lock several times until no more bubbles appear in the fluid. Top up to the correct level.
Repeat this procedure weekly until the fluid is clean and clear - this usually takes 3-4 weeks to fully change the fluid and is kinder to the rack seals than a flushing change and removes more dirt/contamination.

Hope you get to the bottom of the problem one way or another!