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[feeutfo]

Only other thing I noticed driving TB's was mine has a much more pronounced squish noise when releasing full locking.

Very little noise on his.

[Kevin Wood]

Oh sorry. Remove the st relay altogether.

No. Good shout Kev. I could try that today.

Yep, doesn't matter if the ECU is set to max or min. assist, it's still varying the output to the valve with speed. If you can eliminate that, you are back to steering box, pump and mechanical linkages, etc.

However, TIS states that steering boxes are coded to indicate what level of assistance they should be set to, implying that they do vary, and this is compensated for by the assistance setting.. or that's the way I read it, anyway.

Full lock is where the pressure relief valve operates, of course. Maybe there's a clue in the noise you have?

[feeutfo]

I didnt know the relief valve operates at full lock. I thought it just strained the pump until the lock was released.

So it will presumably have a max pressure relief via a spring loaded valve, as well as servo operation?

I wonder if holding/repeatedly bouncing it off full lock might help aggravate the valve. Or just force it open further if it's sticking.

As you can tell I haven't got my simple brain around this yet.

[Kevin Wood]

There will be a relief valve in the PAS pump. Normally, fluid pressure only builds a little when the steering box is working into a load (i.e. forces from the tyres) but when it hits the end stop, obviously, there's an immovable object the box is trying to overcome so the pressure must be limited somewhere. This will indeed be a spring loaded valve in the pump.

On some systems you can connect a gauge and check the pressures are in spec. Not sure on this one. Might have to do a TIS.

[2woody]

This should help you get your head around it.....

there's a valve in the system, a rotary one. One side is connected to the wheels and the other side connected to the steering wheel. They're joined with a flexible shaft.

If you're going straight ahead, the two halves of the valve are both aligned and the valve is effectively closed. The pump produces a nominal pressure which is quite low and most of it is short-circuited past the steer valve.

If you steer either way, your steering input twists the flexible shaft, allowing the two halves of the steer valve to move relative to each other and this opens the valve. The nominal pressure from the pump is fed to the steering box and the pressure assists your steering input.

Now here's the important bit. As soon as you stop moving the steering wheel, the wheels will become aligned to where you want and the two halves of the steer valve catch up to each other. The assistance drops to near nothing, but of course the car is now going round in a circle. You need to reverse the process to get back to a straight line.

It's actually easy to think about it as "steer input" or "no steer input". A steer input is when you're actually moving the steering wheel and the valve is open. Merely holding the steering wheel to one side isn't an input as nothing is happening inside either the box or the pump.

The steering pump is sized to provide the greatest pressure when the valve is fully open, which is either when the steering wheel is being moved fast enough to open the steer valve fully or when you've reached full lock. The pump has a "trick" pressure-setting valve in it, providing the nominal pressure at all times irrespective of the flow rate, only being overloaded at full output ( i.e. full lock ). There is also a master pressure relief valve, preventing the pump stalling out. The normal tests for a power-assisted steering system are for the nominal pressure ( as a guess 5 bar ) and for the master pressure relief ( as a guess 125bar ). It's quite a big pump.

The servotronic valve is a bit of a fudge in that it allows some of the nominal pressure to bleed back to the reservoir without going near the steer valve. It opens and shuts regularly, at a rate controlled by the "relay". More "open", less "closed" = harder to turn steering = more steer "feel".

Removing the relay or disconnecting the solenoid is a good way to diagnose the system as for safety's sake it reverts to a non-servotronic mode whenever there's a fault.

[feeutfo]

Removed both s t relays from very similar spec cars I have here and drove them both with no assistance. Mine bring 3.2 elite. Other being 3.2mv6.

Not as bad as I thought it would be. Initially I thought mine was still stiffer. But after jumping between both cars at least a dozen times. I can't really say I can tell them apart.

Both gave my dodgy shoulders arm ache to the same level.

Re fitted the relays to the opposite cars. So they are swapped. No different. Mine still stiff. Tother normal. So no change.

[feeutfo]

So guessing that means we have a difference in hydrolics on mine.

Suggests swap relief valve. ...?

[Entwood]

Was there ANY difference in yours with either ST relay to without a relay .... I'm wondering if something is up with yours and you are effectively driving with no assistance all the time   ie ... no electronics/electrics

If this is the case (and its nowt but a guess) .. then going by 2Woody's script ....

The servotronic valve is a bit of a fudge in that it allows some of the nominal pressure to bleed back to the reservoir without going near the steer valve. It opens and shuts regularly, at a rate controlled by the "relay". More "open", less "closed" = harder to turn steering = more steer "feel".

perhaps your servotronic valve itself is stuck .. or not "bleeding back" ... because it has no power ??

(or its plain FUBAR ??)

[feeutfo]

Replacing str brought back some assistance. Back to where it was. But with the mv6 str fitted.

[Entwood]

mmm so some assistance seems to imply the valve is moving .. but is "open" more than it should be .. going by 2woody's script again ....  or perhaps the valve is leaking internally and bypassing when it shouldn't ....   

[feeutfo]

mmm so some assistance seems to imply the valve is moving .. but is "open" more than it should be .. going by 2woody's script again ....  or perhaps the valve is leaking internally and bypassing when it shouldn't ....   

Yes it does seem to point to that valve. If changed and resolved, I would then expect the pas to be massively over assisted as its currently set to max assist. But it is stiffer than minimum assist/lighter than no assistance at all.

[feeutfo]

Why would they do this? Btw.

[RobG]

All depends who clipped the relay carriers in as to their arrangement, as it`s only 3 relays guess the orientation isn`t that important

[Spireite]

Same boat as I am in.

TIS2000 explains, remove plastic engine tray, remove heatsheild from steering box, unplug solenoid, remove 4 screws, and remove filter aswell, replace solenoid with cleaned filter, tighten screws to 2.5 Nm and refit heatsheild.

No mention of fluid loss, unless you'd expect it anyway?

Thinking of swapping mine out myself, as didn't feel any difference after purchasing and fitting new ZF servotronic relay from vauxhall at the weekend.

Will follow your post with interest!!!

If you replace the solenoid, let me know if it can be done in situ as TIS explains.

Cheers

Dean

[RobG]

Same boat as I am in.

TIS2000 explains, remove plastic engine tray, remove heatsheild from steering box, unplug solenoid, remove 4 screws, and remove filter aswell, replace solenoid with cleaned filter, tighten screws to 2.5 Nm and refit heatsheild.

No mention of fluid loss, unless you'd expect it anyway?

Thinking of swapping mine out myself, as didn't feel any difference after purchasing and fitting new ZF servotronic relay from vauxhall at the weekend.

Will follow your post with interest!!!

If you replace the solenoid, let me know if it can be done in situ as TIS explains.

Cheers

Dean

and the cost