Power Steering Pump whining loudly

[vw_man99]

Hi All, My son's B7 S4 has been on the road for couple of months after engine refresh and recently the power steering started making really loud humming on turns. Found the hose clamps going to the front cooler were little lose and one hose was cracked near the end. Trimmed hoses and replaced clamps and no more leaks last couple days but humming still there. It probably ran dry and pump is ruined. I do see foaming in the reservoir but no leaks. After watching all the videos and threads we could find, plan is to swap in a used pump this weekend. Couple questions:
- With the foaming and no leaks, its most likely the pump?
- Does the order of connections to the front cooler matter? I don't think so since its a loop
- I could not find a pump rebuild kit, has anyone taken it apart to compare the seals to the A4 pumps?

I did check with 'power steering seals . com' and they have most the other Audi seal rebuild kits but nothing specific for the B7 S4. I may take it to a local steering rebuild specialist to see what they say.

Thanks in advance

[Audibot]

Foaming indicates an air leak is somewhere in the system. It could only be sucking in. Mine did this--wasn't leaking for a while until it was.

Did you bleed the rack (lot of full lock-to-locks)?

Have you checked the front seal? I fixed my line leaks and now the front shaft seal is leaking.

I have heard folks trying the Liqui Moly power steering seal to help theirs.

[vw_man99]

We did lock-to-lock and used Pentosin fluid. Will try it again today.
Have bottle of LiquiMoly fluid (not seal) coming today also.
Is that the shaft front seal available separately?

[Audibot]

Idk if it's sold separately. I got a set for my RS's pump. What part # do you have for the pump?

[vw_man99]

Sticker on the used pump is rubbed out.
From FCP the part number should be ZF 4Z7145156E

Just found a supplier with the Liquimoly stop leak. Will try that first.

Update
Yesterday fluid was empty again. Noticed both hoses going to the front oil cooler were soaked towards the lower front and mid-way but cannot see any leaks due to the jacketed hoses. The bottle does not seem to be leaking. Replaced screw clamps with the oem spring clamps. Don't see any fluid around the pump area. Should I just cut the hose jackets to look for hose leaks? These hoses are expensive so can't just replace. Picking up the stop leak today. Will get some help bleeding while looking under for leaks

[vw_man99]

Pulled off the wheel/liner/cover to check for leaks at the rack and it was dry. Fluid was dripping and sucking air at the connections to the cooler. Rubber hoses are old and not squeezing down. Replaced the generic screw clamps with oem spring type which reduced leak but still dripped so ended up using both on each connection for now. The cheapo screw clamp tab/ridges dig into the old tube so wrapped duct tape under the screw clamp :-)

Have ordered better collar screw clamps (Glarks on amz) that don't have the ridges. No foam in the bottle and no crazy whining.
Next I will try to find replacement hoses that go to the cooler.

2nd helper made the difference. Thanks for the help!