B6 S4 Power Steering Pump Issues

[MORO_B6]

Hello,

I am running into a strange problem with my power steering. (B6 S4)

About 9 months ago my power steering failed. It was the small sleeve shaft that goes from the pump to the timing gear. The splines inside were stripped, I assume due to my pump seizing. I replaced only the sleeve and everything was okay.

A few weeks ago my power steering went out again. After taking it all apart, it was the same issue. Splines stripped out in the shaft sleeve. This time I replaced both the pump (with a Bosch reman one I got from a local audi mechanic) and the pump shaft sleeve.

I got it all in fine, but now I am running into issues bleeding.

When I bleed it with the car off, it seems to act how it should. Bubbles get pushed out, fluid level goes down, it gets easier to turn. However, when I turn on the car, it will not bleed. The first time I try to bleed it with the car on, when the bubbles subside, somehow the level of fluid is always higher than it was with me bleeding it when the car is off. I've tried for hours to bleed the system.

It seems as if the system is pulling in air, but only when the car is on. Is that a possibility? Or, could the pump I bought be bad?

When the car is running it seems there is a lot of vibration on the hard feed line where it leads into the top of the pump through the banjo bolt. It almost seems like the pump is starving for fluid in this spot, or somehow there is aeration here. But no fluid leaks out of the where the banjo bolt meets the pump.

Any help, suggestions would be much appreciated. I'm about out of ideas.

I don't think it's the rack as it worked fine before and theres no leaks near the tie rods. I don't think it's a leak in the lines as I can't find a leak and there was no leak before. I don't think it's the screen in the reservoir as it bleeds properly with the car off, when you'd think it would be harder for the system to push fluid through the screen. But I could be wrong on any of those.

[Dondbg]

R u sure the replacement pump you installed is correct part and / or it is not faulty what you describe sounds like a bad pump to me.

When car is off you are turning the steering lock to lock in this case the rack is doing the job.

[MORO_B6]

@Dondbg, firstly thank you for your reply.

No, I am not at all sure that the replacement part I got is not faulty, as I got it from a shop that had it already. I am pretty sure it is the correct part as it looks the same, and bolts up correctly. I don't know the history of where they got it from.

One thing I did notice that I forgot to mention in my original post. When turning the splines on the pump, this new pump had more resistance than my old one (when I had them completely removed just spinning by hand). The splines where the shaft sleeve goes.

What you said about the rack. If I'm understanding correctly, when the car is off that is what is doing all the pushing of fluid around. Is that correct? I just can't think of any possibilities besides a bad pump.

[Dondbg]

What kind of resistance ? It is just harder to spin all the way or it catch and release while spinning ?

Last time I filled and bled my S4 while was almost empty I raised the front of the car and turned wheel lock to lock after I filled the reservoir where I do see fluid being sucked in, then top up, start / run the car for 3 seconds no more and then shut, turn lock to lock then, top up and repeat till it stops taking fluid.

Reading your original post - What you are describing (vibration) it tells me like the fluid flow is blocked and vibration starts from pressure being built up - just a theory here but none of the hoses / pipes are blocked ?
Why I have a feeling whoever rebuilt this pump didn’t assemble it correctly.

[All_Black_A4]

What kind of resistance ? It is just harder to spin all the way or it catch and release while spinning ?

Last time I filled and bled my S4 while was almost empty I raised the front of the car and turned wheel lock to lock after I filled the reservoir where I do see fluid being sucked in, then top up, start / run the car for 3 seconds no more and then shut, turn lock to lock then, top up and repeat till it stops taking fluid.

Reading your original post - What you are describing (vibration) it tells me like the fluid flow is blocked and vibration starts from pressure being built up - just a theory here but none of the hoses / pipes are blocked ?
Why I have a feeling whoever rebuilt this pump didn’t assemble it correctly.

I think it's 10 turns of the wheel from lock to lock then start the car for 2 seconds then repeat til no more air is present....topping up fluid if/when needed as well.

I think air is only drawn in when the car is running as the pump will be running obviously.

I had a hard time bleeding my power steering system after I did my timing job this summer. Tracked it down to the lines going into the power steering cooler as well as the line running under the car weren't tight enough and air was being drawn in.
Soon as they were tightened down and they didn't need much, I was golden. Went from a growly pump to a quite pump and has been fine ever since.
Not saying that's your problem but since you've had things apart doesn't hurt to check connections etc

[MORO_B6]

What kind of resistance ? It is just harder to spin all the way or it catch and release while spinning ?

Last time I filled and bled my S4 while was almost empty I raised the front of the car and turned wheel lock to lock after I filled the reservoir where I do see fluid being sucked in, then top up, start / run the car for 3 seconds no more and then shut, turn lock to lock then, top up and repeat till it stops taking fluid.

Reading your original post - What you are describing (vibration) it tells me like the fluid flow is blocked and vibration starts from pressure being built up - just a theory here but none of the hoses / pipes are blocked ?
Why I have a feeling whoever rebuilt this pump didn’t assemble it correctly.

It did not catch at all while spinning it, was just harder to spin in general.

When I had wheels off the ground bleeding it, it sucked down fluid and seemed to bleed properly. After allowing the bubbles to leave I then filled to the max line on the cap. Then I turned on the car (front tires still off the ground) and tried to bleed it. When I took off the cap and let the bubbles subside, it was above the max line.

None of the hoses are blocked. I had the banjo bolt pulled out of the end of the hard line and it was just fine. My previous pump had 0 issues until it suddenly seized (I assume) and sheared through the splines.

[MORO_B6]

I will be sure to check these connections over the weekend when I do have time to look at the car. But I'm almost certain that's not the problem this time as it was operating properly with the old pump.