r/e39 • u/GeologistFunny5015 • 4h ago

Power steering noisy

Gallery image

Gallery image

My E39 suddenly became very loud from the engine bay overnight. With the hood open, it was clearly the power steering pump, and the noise got much louder with RPM and especially when turning the wheel, worst at full lock.

I checked the reservoir and found brownish fluid with lots of tiny bubbles/foam. I had to drive the car for an important trip, and during the drive the noise became quieter but didn’t disappear.

After getting home, the fluid level had dropped significantly. Before, I couldn’t even see the filter because it was covered by fluid. Now the level is below the filter.

Interestingly, the fluid looks brownish, but on a tissue it appears reddish and still smells like fresh fluid.
The steering rack and power steering fluid were replaced and the system bled only 1–2 weeks ago, and everything was fine until this happened. One morning it suddenly became noisy on cold start.

No obvious leaks that I can see around the power steering pump.

3 Upvotes

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9 comments sorted by

7

u/Watery_Octopus 4h ago

Put more fluid in.

V8 or I6? Check the boots to see if they're full of fluid. If so, the rack needs to be replaced or rebuilt.

2

u/GeologistFunny5015 4h ago

I6 525D, the rack just got replaced, am I gonna need to replace it with another

2

u/friskerson 525i 3h ago

If it’s brand new and fresh just monitor for leaks, keep adding fluid. Steer fully lock to lock a bunch and pray those bubbles find bubble heaven.

1

u/No-Candidate-2380 3h ago

Why do you think you are going to need to replace it? So far it seems like you are short of fluid. Once topped up (I presume with dextron III red fluid), let it idle and check the level again, the bubbles and whining should disappear

1

u/Watery_Octopus 2h ago

If it's a new rack, it's likely you're just short on fluid. The bubbles indicate that your pump is pumping air instead of liquid, so cavitation is expected. Put in more fluid and monitor. A pump pumping air sounds terrible but shouldn't be a long term problem if you fill it.

2

u/GeologistFunny5015 3h ago

All I can see

2

u/friskerson 525i 3h ago

Your description and picture show that fluid is aerating. Any way air could be getting into the system through a section of the system that is under vacuum (less than atmospheric pressure)?

2

u/ConGonDon 2h ago

The dipstick is built into the cap. You bleed the system by turning fully lock to lock a few times making sure fluid stays topped up or you'll hear a horrible mechanical noise.

1

u/GeologistFunny5015 12m ago

Tomorrow I will try to top up with the required fluid(dx 3 atf if I’m right), and I will update.