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Bleeding the 164 Q4 power steering system

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Bleeding the 164 Q4 power steering system

Postby AlfaWhiz » Fri Apr 20, 2018 9:48 pm

I have a problem with a noisy power steering pump after the recent steering rack rebuild. The rack has been refurbished, all power steering hoses are renewed, Viscomatic has been successfully bled via the F/L Tester, system was bled by turning the steering wheel side to side, fluid level is correct and the auxiliary belt is tensioned properly.

Despite all this, there still is a noticeable, quite loud whine when turning the wheels left or right, or after increasing the revs when the pump loads up.

The pump itself was working perfectly fine and quiet just before the steering rack has been taken out of the car and the car has not been driven with an empty reservoir in the meantime.

Do you have any ideas what should I check or what could cause this annoying noise?
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Re: Bleeding the 164 Q4 power steering system

Postby alfa164superwebmaster » Sat Apr 21, 2018 7:08 am

Sounds like incorrect oil, you need the special green hydraulic fluid. Not regular ATF oil.
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Re: Bleeding the 164 Q4 power steering system

Postby AlfaWhiz » Sun Apr 22, 2018 7:52 pm

It's the correct green oil, same I've also used before without any issues so it's not the oil itself. Has to be something else.

Current plan is to do some careful test driving and try to bleed the air out once more, then I'll look at the belt tension again or air leaks on the pump inlet side, all hoses coming to/from the power steering rack have been replaced, there may be something wrong there.
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Re: Bleeding the 164 Q4 power steering system

Postby AlfaWhiz » Tue Apr 24, 2018 5:38 pm

After some test drives and repeated bleeding of the pump and Viscomatic, I come to believe there is now no air in the system. The source of the annoying noise is elsewhere.

One additional thing came up when test driving which I have now investigated very carefully. There is a loud ticking, clicking or buzzing noise coming out of the Viscomatic group in the rear. Characteristic of this noise:

a) it increases (pitch, loudness) together with engine revs and not car speed
b) it is present only when the Viscomatic accumulator recharge valve is NOT recharging, i.e. is recirculating the fluid back to the reservoir
c) it fully disappears for a brief second when the recharge valve is charging the accumulator
d) additional noise from power steering pump, whining under load, when turning, changing with engine revs
e) additionally I can hear a pop and feel a jerk on the steering wheel when I just finish turning the wheel, i.e. you turn the wheel slightly and when you stop and the power assist stops working, there is a slight jerk on the wheel and slight noise

There is no warning light.

After having the car up on a lift, it turns out that the source of this annoying noise is the high pressure inlet steel pipe coming from the power steering to the Viscomatic group in the back, the pipe is resonating and vibrating loudly.

The steering rack has been refurbished and all flexible hoses replaced. I've checked all hoses, there is no visible flow obstruction, hoses are not crimped, etc.

I believe there is something wrong going on with the pressure in the system causing some pressure fluctuation or flow obstruction which causes the vibration. It sounds like the pump does not get enough flow and is starving under load, but what can cause this and the vibration on the high pressure line to the Viscomatic?

Maybe one of you with more insight into hydraulics will be able to help. Any ideas what could be the cause of this weird problem?
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Re: Bleeding the 164 Q4 power steering system

Postby Alfan » Tue Apr 24, 2018 7:29 pm

I assume that you have checked the level again? :wink:

If you believe that the system has no more air in it, my guess is that something is obstructing the flow - if you haven't done anything to the steering pipe mentioned, maybe that needs to be flushed...?
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 85.000km
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Re: Bleeding the 164 Q4 power steering system

Postby AlfaWhiz » Sat Apr 28, 2018 6:55 am

The suspicion at the moment is that the line feeding high pressure to the VIscomatic, coming directly from the pump, has been reproduced wrongly. This line has a piece of flexible tubing which contains two choke elements, reducing the flow in the system before reduction of the hose diameter, the pipe is covered in protective wrapping. I strongly suspect that the chokes have been removed and replaced with a piece of hose when the shop refurbished the hoses... I cannot see or feel the chokes on this hose any more.

This would cause excessive flow in the system resulting in the vibration observed (remember, vibration and noise disappears for a second when the pressure is relieved when recharging the accumulator), additionally now leakage has appeared at the Viscomatic unit where the pipes connect, further showing results of excessive flow and pressure.

Does any of you have the part number 60605589 in stock, used, and could have a look at what type of chokes / flow reductors are used there?

It's part number 1 from this ePER picture, flow reductors I believe are located within and what is visible as the thick part of the line is actually the outer protective sleeve:

Image

The mistake on my part was not double-checking afterwards and not doing photos of everything as I usually do. :cry:

Now I need to have a look at an original hose for comparison.

Many thanks in advance.
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Re: Bleeding the 164 Q4 power steering system

Postby AlfaWhiz » Sat May 05, 2018 2:20 pm

Anyone who could help with used 60605589?
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Re: Bleeding the 164 Q4 power steering system

Postby AlfaWhiz » Sun Sep 02, 2018 6:26 pm

So just to recap for anyone who may run into a similar issue.

What fixed it in the end was getting a brand new high pressure Viscomatic supply hose (the one after the pump) 60605589. Expensive, but worth every cent.

Most probably the replacement I had made had insufficient flow reduction and caused excessive flow and pressure, thus resulting in vibrations of the Viscomatic lines in the rear part of the underbody (metal lines were vibrating and resonating through the chassis quite loudly).

Installed brand new part ordered from Alfa (luckily still available), works like a charm now. Those hydraulic circuits can be tricky at times, the flow is balanced and apparently a very minor difference (we could not work out what exactly we did differently on the replacement part) can make a massive difference. :idea:

Maybe this is what actually caused my stuck piston issue I have now (excessive flow or pressure), as this problem appeared right at the same time the replacement line was installed. Now the line is fixed, will be looking at fixing the piston movement issue with a PWM controller as discussed in the separate thread. :)
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Re: Bleeding the 164 Q4 power steering system

Postby alfa east » Thu Sep 13, 2018 12:19 pm

Sometimes it's amazing how original parts make a massive difference. Seems you're well on your way to solve a couple of persistent problems you had!
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