Power steering circuit - air ingress

4.2 V8 40v biturbo - 450 bhp
4.2 V8 40v biturbo - 480 bhp (plus)
Lander91
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Power steering circuit - air ingress

Post by Lander91 » Fri May 14, 2021 9:20 am

Hi all
I've got the PS pump supercharger whine, so I thought I would start a thread that relates the journey towards shutting the f*cken thing up.

Some background:
I have a good used pump on its way.
I have a new res to install, all the relevant crush washers and hose clamps for if/when the new to me pump goes on.
There are no dripping leaks from anywhere in the PS circuit
I will take a video and pics of the current pump in operation showing the state of the fluid as I'm not sure what constitutes 'bubbles' in the fluid - its not foaming or dropping in level.

I'm looking for opinions on where air may be getting into the system, e.g. areas to focus on during new pump installation. I don't want to miss anything and end up with the whine still once everything is buttoned up.

As mentioned, I don't have any dripping leaks, but there is evidence of seepage in certain areas. From my own reckoning I can see the only places for air to be getting IN is in the attached pic - where the pump is sucking fluid. To me if its leaking anywhere but the rack seals I cant figure how air gets in if fluid would be squirting out at any level, and as mentioned there are no dripping leaks.

Anyway I'll be replacing the crush washers on the pump, the res and the 2 hose clamps on the res.

Thanks in advance.
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Re: Power steering circuit - air ingress

Post by Mɐʇʇ » Fri May 14, 2021 11:53 am

Just for reference, the TRW part number of a new one is JPR725.

Not quite what you're asking, but when filling, I find it takes a little patience to get the air out since the difference between level being too high and foaming over the top while you're filling, vs too low and it sucking air back in, is quite small. I usualy stuff some rags round it because I inevitably overfill a bit so when it foams up it overflows a little:
1. First fill
2. start up briefly
3. Stop & Top off
4. Start up & turn wheels L to R, lock to lock (have car on stands)
5. Stop & Top off
6. Start up & turn wheels L to R, lock to lock
7. Stop & Go for a cup of coffee to let the air in the reservoir settle out.
Repeat 5,6,7 until there's no bubbles left.

I have found that if I keep running it while "foamy", the foam doesn't seem to disappate.
Once purged, you can see the flow of fluid through the reservoir with the lid off and it should have no bubbles in at all - mine definately doesn't

Pipes (5) & (10 )are low pressure lines (well, one small pressure, one small vac)

I also always find unions (9), even with fresh clips done up nice and tight, still always ends up with the odd drop over time.
Probably needs a pair of clips on it.

In my case, a new pump solved the power steering shenigans.
Last edited by Mɐʇʇ on Fri May 14, 2021 5:12 pm, edited 4 times in total.
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Shoppinit
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Re: Power steering circuit - air ingress

Post by Shoppinit » Fri May 14, 2021 1:46 pm

^Good advice.

DON'T turn the wheels on the ground.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
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Lander91
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Re: Power steering circuit - air ingress

Post by Lander91 » Sat May 15, 2021 4:31 am

That is Matt & Shop, I'll keep the car on stands till I've bled the system.

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Re: Power steering circuit - air ingress

Post by Mɐʇʇ » Sat May 15, 2021 9:02 am

This was the DIY I wrote some months back.
viewtopic.php?f=2&t=135392&p=941344

There’s really only 1 tricky to access bolt, the rest are all OK.
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Lander91
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Re: Power steering circuit - air ingress

Post by Lander91 » Sat May 15, 2021 9:21 am

Perfect thanks Matt

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Re: Power steering circuit - air ingress

Post by Lander91 » Thu Sep 23, 2021 4:32 am

Quick update. I've installed the 2nd hand 'good' pump, and despite promising results from the beginning, the whine still develops. I followed not only the bleed steps here as per thee advice from Matt and Shop, but the 1st initial step as per ELSA which is to cycle the steering with the engine off, then run for 10sec then switch of and check levels etc.

Anyway, initially the steering eventually cycled left and right with no whine, and no whine sitting at idle, no obvious bubbles or foaming. Not one to trust these cars, I pulled the car out to do some 5 point turns in the area in front of the garage. Eventually the whine and a sound like when the steering is hitting the pressure limit in the pump, only much louder started to emanate.

The car is back in the garage up on stands and I've done 3 bleed cycles of lock to lock 10 times. No whine, again. However as per the attached pic, I'm wondering if I still need to continue with the bleed process some more.

The question is, should there be absolutely zero evidence of bubbles or is what's in this pic 'normal'.

I'm buggered if I know where air could be getting into the system. To me the only points where air can be introduced is at the suction pipe junction on the res, the suction pipe banjo bolt on the pump, or gaskets/seals inside the pump. Anyone hazard a guess as to where else air could be getting in?

FYI there are no hydraulic fluid leaks and AFAIK the rack experiences high pressure in almost all areas exposed to the fluid, so if there were any leaks that could introduce air there would be subsequent leaks in the same locations.
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Re: Power steering circuit - air ingress

Post by Mɐʇʇ » Thu Sep 23, 2021 9:02 am

I'm 99.999% sure there's no aeration at all on mine. I'll be out in it at the weekend so will check.
That doesn't look overfull though - and if it's low, it's easy to pull some air in the way the fluid cycles through - maybe you just need to top it up a bit more?
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Lander91
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Re: Power steering circuit - air ingress

Post by Lander91 » Thu Sep 23, 2021 10:12 am

Thanks Matt, level is bang on the top mark after running and the bleeding process, which I'm still doing, up to 5 now.

I've had a real close look at my old pump to figure out the possible ingress points. From what I reckon there are 2, the shaft front seal and the main oring that seals the 2 halves together. I've a gasket set due here soon, will send the pump to a specialist to fit them and see how I get on.

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Re: Power steering circuit - air ingress

Post by Mɐʇʇ » Thu Sep 23, 2021 12:37 pm

Overfill it a bit.
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Riggs
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Re: Power steering circuit - air ingress

Post by Riggs » Thu Sep 23, 2021 9:30 pm

Hi Mate
When I had my engine out I did all my P.A.S pipes and fitted a new pump and had the exact same problem that you have now. I run my own garage and have had this on numerous other vehicles and it’s always ended up being just a noisy pump. I fitted a new TRW pump, bled the system and job done. The pump from what I remember wasn’t loads of money. I still have my old one and the only reason I changed it was it made the scream/pressure noise on full lock. The first one I fitted was complete crap and was worse than my original.

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Re: Power steering circuit - air ingress

Post by Lander91 » Fri Sep 24, 2021 4:34 am

Cheers mate, I feel as though you are on to something. There's, what I think, evidence of cavitation inside the pump and who knows just how sensitive these things are to clearances etc. Imagine some bits of swarf from wear in the fluid, there's some pretty small orifices the fluid goes through. Id go as far as saying that these would be points were wear occurs.
I've the seal kit now, there's a YouTube vid of a guy rebuilding a Porsche 944 pump that's more or less the same as the ones in the 6. It's pretty simple to replace all the seals which I'll do, then see if the 10 'bleeds' has helped. If not I'll fit the re-sealed pump, then bite the bullet and buy a new one if that fails.
I f*cken hate the noise!

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Re: Power steering circuit - air ingress

Post by Mɐʇʇ » Fri Sep 24, 2021 9:32 am

Yeah, but cavitation isn't the same as ventilation/aeration. Cavitation inside a pump is bad - because the little vacuum bubbles collapse quite violently and can erode the machined surfaces inside the pump. I'm being absolutely serious when I suggest, just temporarily, overfilling the reservoir by 10mm. I really think the design of the reservoir is both quite clever, but quite marginal - and there is opportunity for the res to draw more air into the circuit, especially when it's still got a little air in. Nothing to lose, even if I'm (as I probably am) wrong...?
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Shoppinit
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Re: Power steering circuit - air ingress

Post by Shoppinit » Fri Sep 24, 2021 9:38 am

Also, a leak in a high pressure environment can act like a one-way valve: sealed under pressure but open under vacuum.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

Lander91
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Posts: 369
Joined: Sat Oct 03, 2020 8:12 am

Re: Power steering circuit - air ingress

Post by Lander91 » Fri Sep 24, 2021 9:42 am

I've put the level to 10mm over the top line. Lost count of the bleeds I've done this afternoon, probably due to the fumes of all the cold starts. :drink:

Made a video of the res and bubbles as of now.

https://youtube.com/shorts/Qvb5NKCef9g?feature=share

Pump with new seals goes in tomorrow if the noise is still there when I take it off the stands. Failing this, new pump. Then if that's no good then the rack? :bash:

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