Refreshing Power Steering fluid

[Welly]

During all of the cars I've had with PAS I've never changed any of their PAS fluid.

The Volvo still has the same fluid the factory put in 15 years ago so going by its black-not-green colour I've just ordered 2 ltrs of fluid and a Syringe-with-hose for extracting the old.....refill.....turn steering.....extract....refill etc until I can change 'most' of the old stuff for new.

Has anyone noticed any difference after changing the fluid in any car?

Picked up a great tip also where you park the front wheels directly over a folded black bin bag and this way you can wang the steering left-right as much as you want without putting the tyres/rack under strain

[Doggy]

Don't.

The biggest enemy of hydraulic system is dirt. It's virtually impossible to ensure the clinical cleanliness necessary to avoid all contamination.

If it ain't broke.....

[steve_earwig]

...fix it until it is

I'm sure the 15 year old mud is fine You have the fluid, just be careful. I have a feeling it's one of those jobs that you will only feel a difference in your wallet (and maybe your soul )

Interesting about the black bin bags, did you try it yet or is it still in the theoretical stage?

[Welly]

Don't.

I know I know but the little reservoir is clean, its nice and high up and feeds a 'bath' of fluid lower down hidden in the wheel arch liner. The engine bay is clean too, think I'll sheet everywhere off like an operating table

I have a feeling it's one of those jobs that you will only feel a difference in your wallet (and maybe your soul )

Interesting about the black bin bags, did you try it yet or is it still in the theoretical stage?

£42.00 difference, that'd pay for 2 x Chinese takeaways...oh wait.

Not tried any of this yet but have bin bags at the ready

Be interesting to see how much PAS fluid I can get in my eyes/over the paintwork etc - a bit like last weekend on the DV6 when trying to liberate the oil filter cartridge from its housing and it suddenly let go sending a 'shower' of blackened diesel oil all over the recently-cleaned block paving.

Anyway everyone over on the Volvo Forum is changing their PAS fluid which feeds a very expensive electro-hydro pump coded to the car so WCPGW?

[steve_earwig]

Can I post pictures of the Amoco Cadiz on both of your current threads?

[trufflehunt]

Has anyone noticed any difference after changing the fluid in any car?

Changed the PAS fluid on my 238,000 mile ( lunar module ) Golf last summer.
Used the same method as you.
Yes, it did seem to improve the feel of the steering.

[Wul]

Has anyone noticed any difference after changing the fluid in any car?

Last year there's a few leak in the low pressure hose and steering rack seal, so naturally after the repair it has to use new fluid. I noticed that steering is a bit lighter to turn when driving. It's also particularly very noticeable when parking.

In the future would I refresh the fluid if there's no leak? Probably not, as I don't think it justifies the price

[Welly]

Well this job was 'one of those' jobs but I got it done:

Schematic of the system:


It was only possible to extract the header bottle's contents and 'some' of the outlet hose to below, this was only about 0.2ltrs so useless as a 'fluid change' because the real action and fluid circulation happens at the pump unit below.

Time to get the wheel arch liner out, the hydro/electric PAS pump is fed by a little header bottle above, the pump then has its own reservoir of fluid in that cream-coloured plastic tank/pump combo:


Get that top hose off and wait to get soaked in fluid:




Syringed the old stuff out:


The old fluid (supposed to be green):


Reconnect everything and refill with new fluid:


Lower car onto wheels, start engine, work steering left/right, remove wheel again, syringe mixed new/old fluid out and refill (again) Bin Bags under the tyres:


*repeat 3 times*

New fluid after final top up:


So, has it made a difference?

Yes! the fluid was 15 years old, the steering actually feels 'firmer' to me and more planted, like 'newer' I guess. I thought it would feel lighter but no it has a nicer more stable feel to it.

[Doggy]

Thorough job there, I is impressed.

Electric PAS pumps still seem unusual to out-of-touch yours truly, but I guess it makes sense to drive the pump at constant speed and not spec it to deliver maximum assistance at tickover which must be the norm with engine driven units.

I just hope yours doesn't expire due to brushwear etc, (if they have brushes), after all your hard work.

[steve_earwig]

Err, you seem to have gone from "don't do it, it'll all go wrong" to "ah, it's done, now something else will go wrong" - right cheerful aint ya

Nicely done Welters, glad you're feeling some benefit from it too

I guess it makes sense to drive the pump at constant speed and not spec it to deliver maximum assistance at tickover which must be the norm with engine driven units.

Engine load too apparently, helps with consumption (I suspect minimally tho)

[Welly]

Pfft "consumption" - what's that?

The pump runs constantly at low-ish speed and when you steer it ramps up a bit....then settles back. I guess it's one less thing to drive off the engine although it don't half pull a strong current when you steer....in winter it dims the headlights for a brief moment until the electrics catch up

If you look closely you'll be reassured* by the FoMoCo etched into the plastic, to be fair even the 16 year old models don't report any issues with these pumps; even if neglected

I've tried selling the idea over on the Forum but typically its fallen on deaf ears so far.

Imaging asking a garage to do this for you! there's no way they'd spend the time doing it like I did (and for so many times) bet they'd be happy to charge enough though.

[Doggy]

So it is a variable speed pump, (which is sensible - traditional hydraulic pumps rely on mechanical relief or offloading valves to wastefully regulate pressure). A variable speed drive is a much 'smarter' alternative. Also a fair chance it's a brushless motor despite the FOrever MOre COst logo.

Normal practice would be to measure/control the delivery pressure, likely using info from steering angle sensor etc. This would imply some ability to compensate for variation in fluid characteristics....

Imaging asking a garage to do this for you! there's no way they'd spend the time doing it like I did (and for so many times) bet they'd be happy to charge enough though.

Tell me about it. I recently suffered the MOT brake fluid check / £60 to change extortion.
Sloppily executed powah steering fluid renewal is bound to be on the list of 'added value services' we'll soon be 'encouraged' to partake in.

Maybe leccy power steering isn't so bad after all?

[Welly]

Maybe leccy power steering isn't so bad after all?

I guess so, so much so I don't need to know much about it....apart from just now............

Volvo Publication:

EHPAS (Electro Hydraulic Power Assisted Steering)
The system has a hydraulic pump driven by an electric motor. The electric motor is controlled by the
control module. The control module adapts the servo power based on the speed of the car and how fast
the steering wheel is being turned.

Control module, electric motor, hydraulic pump and fluid reservoir are all in one unit-which is also a
replacement part.
The unit is positioned under the right-hand front wing.
Some advantages of this type of system are:
• Using software, servo power can be easily adapted to different car variants.
• Takes up very little space and easy to position in the car.
• No drive belt is required.
• Energy consumption is lowered, which leads to reduced fuel consumption.

The pump is the gear type.
Maximum assist pressure is 120 bar.
There is a bypass valve (1) and a check valve (2)
integrated in the pump.

The bypass valve (1) opens when the pressure is
too high and the oil is returned via the check valve
(2) to the pump

The pump motor is a brushless direct current (DC)
motor with four rotor windings.
The speed of the motor is controlled by the control
module using PWM. A hall sensor in the motor
informs the control module of the actual speed and
indirectly the relevant hydraulic pressure.
The speed can vary between approximately 1300
and 4500 rpm as required.

EPS controls the speed of the pump motor and
power consumption via internal power stages -
power transistors.
The power consumption can vary between 6 and
80 A depending on the conditions. A diagnostic
trouble code (DTC) is stored if consumption is
greater than 96 A.

80 AMPS!!

[Doggy]

80 AMPS!!

Not such a big deal, your alternator will be rated at 150A or more.

I was meaning pure electric, (i.e. no hydraulics), power steering:


I've heard the leccy version doesn't give you the 'feel' you get with your layout, but it's going to be cheaper so it will have many 'advantages', like FWD, cataclysmic converters et al

[Welly]

Oh I see, yes, the Renner Twingo has full electric steering and does indeed feel a bit odd.

I don't even know what the Shitroen uses.....daren't look