C70: How to flush power steering fluid?

[StatusRed]

Did this yesterday using method 2, but taking the return pipe off the reservoir instead of doing it at the rack end.. Ear clamp was a right pain to get off but I'm going to replace it with a jubilee clip.

2 litres of CHF IIS fluid used to flush and fill, magnet left in reservoir overnight to collect any metal fragments.

[ASt85]

Originally Posted by StatusRed

Did this yesterday using method 2, but taking the return pipe off the reservoir instead of doing it at the rack end.. Ear clamp was a right pain to get off but I'm going to replace it with a jubilee clip.

2 litres of CHF IIS fluid used to flush and fill, magnet left in reservoir overnight to collect any metal fragments.

If you are doing a powered flush with the engine running make sure the restrictor which sits in the return tube doesn't end up in the collecting bottle as it is not fixed in the tube - it will be forced out under pressure and if not restored to its position causes lower fluid pressure and excess foaming in the reservoir which in turn causes the steering to get heavier.

It needs to be put back into the return hose before you the tube.

[StatusRed]

Originally Posted by ASt85

If you are doing a powered flush with the engine running make sure the restrictor which sits in the return tube doesn't end up in the collecting bottle as it is not fixed in the tube - it will be forced out under pressure and if not restored to its position causes lower fluid pressure and excess foaming in the reservoir which in turn causes the steering to get heavier.

It needs to be put back into the return hose before you the tube.

It was only powered for about 0.5 seconds before I realised it was a very very risky idea as the fluid came out way too fast. I didn't notice anything come out of the return hose. From then on I just did it by turning the wheel without the engine on.

[ASt85]

The reason behind my post above was that in the process of doing a powered flush there was a loud bang as the hose joint to my vented catch bottle blew the hose off the pipe joint to the bung.

As I cleaned up the resulting puddle, luckily most of the fluid had been collected by a plastic tarpaulin, I happened to notice a 4cm long bright metal tube, chamfered at both ends nestling between the reservoir and the coolant tank.

I identified it from a Vida diagram as a "restrictor", a subsequent phone call to FRF further identified it as as a part that sits in the return pipe of the C70 which, when the system is pressurised is forced up against the power steering fluid reservoir return inlet and reduces the rate of fluid return to the reservoir which acts to maintain the correct pressure in the system and by reducing the rate of return also reduces the foaming of the fluid.

The restrictor just sits in the return pipe to the reservoir in some C70s.

FOR FURTHER INFORMATION READ MY POST WITH PHOTOS AT
https://www.volvoforums.org.uk/showthread.php?t=268568

It is bright and shiny it isn't actually brass but a plated steel look alike and looks like a brass ring or washer within the plastic inlet when seated within the inlet tube once the inlet tube has expanded (due to action of fluid on plastic) - if memory serves it's about 1.5inches long i.e around 3 to 4cm in length - it literally narrows the inlet to approx 10 % of the orifice diameter and should be visible in the plastic inlet tube of the reservoir if you take off the upper rubber tube inlet, ie the high pressure return from the steering rack - it maintains the fluid pressure throughout the system prior to the low pressure return/dump to the reservoir for re-circulation via the pump to be re-pressurised to drive the powered rack.

[StatusRed]

Originally Posted by ASt85

The reason behind my post above was that in the process of doing a powered flush there was a loud bang as the hose joint to my vented catch bottle blew the hose off the pipe joint to the bung.

As I cleaned up the resulting puddle, luckily most of the fluid had been collected by a plastic tarpaulin, I happened to notice a 4cm long bright metal tube, chamfered at both ends nestling between the reservoir and the coolant tank.

I identified it from a Vida diagram as a "restrictor", a subsequent phone call to FRF further identified it as as a part that sits in the return pipe of the C70 which, when the system is pressurised is forced up against the power steering fluid reservoir return inlet and reduces the rate of fluid return to the reservoir which acts to maintain the correct pressure in the system and by reducing the rate of return also reduces the foaming of the fluid.

The restrictor just sits in the return pipe to the reservoir in some C70s.

FOR FURTHER INFORMATION READ MY POST WITH PHOTOS AT
https://www.volvoforums.org.uk/showthread.php?t=268568

It is bright and shiny it isn't actually brass but a plated steel look alike and looks like a brass ring or washer within the plastic inlet when seated within the inlet tube once the inlet tube has expanded (due to action of fluid on plastic) - if memory serves it's about 1.5inches long i.e around 3 to 4cm in length - it literally narrows the inlet to approx 10 % of the orifice diameter and should be visible in the plastic inlet tube of the reservoir if you take off the upper rubber tube inlet, ie the high pressure return from the steering rack - it maintains the fluid pressure throughout the system prior to the low pressure return/dump to the reservoir for re-circulation via the pump to be re-pressurised to drive the powered rack.

Cheers I'll take a look when I fit the new jubilee clip over the pipe on Sunday, if it's missing I'll get a new one!

[ASt85]

I'm told that in some reservoirs it actually sits completely in the inlet tube so looks like a brass washer or ring level with the end of the plastic reservoir inlet.

I suspect the restrictor moves into the inlet as the older plastic reservoirs expand - the primary cause of the leak in the sealed joint between the top and bottom of the reservoir.

The restrictor isn't fitted in the later C70s nor any of the P2 range.

[C70Noob]

Originally Posted by MikeS100

All done. Start to finish including getting everything ready and tidying up at the end took 35-40 minutes I spoke to the technician at my local volvo dealer and he said when they do a flush they just disconnect the return hose off the reservoir and then keep topping up the reservoir while someone turns the steering so this is what I did and it worked perfectly. I used 2.5 litres of CHF just to make sure but may have got away with less. It was running out a nice green colour at the end. I jacked the front up as well so the wheels could turn easily without having to run the engine or wear out my tyres. All in all I'm pleased with a job well done

I know this is a super old post, but did you use the Halfords stuff in the end or the Volvo CHF? I need to do mine and wondering if I can get away with being a cheapskate

[ASt85]

Originally Posted by C70Noob

I know this is a super old post, but did you use the Halfords stuff in the end or the Volvo CHF? I need to do mine and wondering if I can get away with being a cheapskate

I always use the Comma MVCHF, which varies in price but is usually around £10 to £11 per litre, it is currently (11 January 2020) £10.99 at Halfords but is the same price from Amazon Prime delivered.

Our local Halfords is a 10 mile round trip so Amazon works out way cheaper over the year with all the other shopping on-line !

[Paffel]

Pm sent

[MikeS100]

Originally Posted by C70Noob

I know this is a super old post, but did you use the Halfords stuff in the end or the Volvo CHF? I need to do mine and wondering if I can get away with being a cheapskate

I used Volvo CHF. It might be all the same, but for a few litres the difference in price is quite small really and then you know it's got good fluid in it. I always order from FRF Volvo in Swansea with the C3 discount code for forum members, brings the price down quite a bit