E34 540i power steering Qs

[Nic_s]

I've recently discovered that if I switch off the engine and open the power steering fluid's reservoir and wait a while.... the fluid would start to push back into the reservoir and after and hour or so (Depending on how much fluid is in the system) it would over flow. I haven't left it long enough to try and see if it eventually stops. I always thought I had a very slow leaking pipe that was messing fluid everywhere, but now I think the fluid is pushing out the reservoir if the car stands long enough. For now I just made sure the lid is nice and tight, but this doesn't seem right to me. :thinking:

I tried google, but I keep ending up on pages about the rear self leveling system for either the M5 or touring E34's. Anyone know more about the fluid pushing itself back like this???

If you want to see if your E34 does this, it's pretty easy to test. Start the engine and turn the wheel a few times. Switch it off and open the bonnet. Then open the the reservoir and keep an eye on the level. You should see it rise VERY slowly... or at least mine does. Don't open the the reservoir first thing in the morning or you could end up with loads of fluid going everywhere if your car does this.


Another thing my car does is it would sometimes give a little tug at the steering wheel while I'm standing still at the lights or stop sign, but I've never noticed it while driving. This is definitely the power steering. It's like it tries and turns the wheel, but then gives up after half a second. Does this make sens???

Any info would be appreciated. Thanks

 

[Fordkoppie]

:thinking:

 

[Nic_s]

:thinking:

I know right??? Why would the fluid push back like this?? Makes no sens.

Maybe I'll try and take a video over the weekend and then increase the speed so you all can see what I mean.

 

[Raybimmer]

Nic I will check mine and let you know , I have never had any steering wheel movement though .

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My level was 60 mm from the container edge to the fluid . After starting and idling her for 5 minutes ( reserve light comes on so about 15 min idle to empty lol ) with about 10 complete steering movements and then switch off and measure after 5 minutes the level was 75 mm . will check in 30 minutes .

---

30 minutes later the level is still 75 mm .
Nic this shows that fluid is used and may drain back over a time , was your level filled when the car was hot , when cooled down it overflowed due to the excess fluid being pushed back . Will check in an hour .

 

[Raybimmer]

Just checked earlier and level at about 72/73 mm .

 

[abmi0000]

I know for fluid to fluctuate whilst the steering wheel is being turned and that's why the level is always maxed below the top of the reservoir.

Do you think that the pump is draining is some way?

 

[Nic_s]

Once I start the engine the level drops maybe 8cm and stays there while you turn the wheel. Next morning the fluid is pressing against the top. This can't be right which either means something us wrong or I'm missing something. Only thing I can think is air trying to come out, but from what I understand, to get air out you start up the engine and turn the wheel?

I didn't have time to test it yet

 

[Nic_s]

I drove the car on Saturday and the fluid was maybe about 8cm from the top as I stopped at home. Sunday morning came and as I was slowly opening the reservoir fluid started to run past the lid. So it was pushing up against the lid again. Started the engine, level goes down, turn off engine, level starts to creep back up after about 10min. :shakehead:

 

[rick540]

This is 100% normal and how it's supposed to work.

Go look up the BMW H31 braking system your car has.

The fluid is stored under pressure in a hydrogen pressure accumulator on start up and when the engine is running. This is like a hydraulic version of the vaccum brake booster which your car does not have.

When you turn the car off and leave it the 1100psi pressure gradually leaks and pushes the pressure stored fluid back out into the system till the next start.

The accumulator or "bomb" can store about half a liter

 

[Nic_s]

Thanks Rick. So I guess one should check the level while it's running and then fill it up to about 25mm from the top?? I think it was you that said 25mm.

What about:

Another thing my car does is it would sometimes give a little tug at the steering wheel while I'm standing still at the lights or stop sign, but I've never noticed it while driving. This is definitely the power steering. It's like it tries and turns the wheel, but then gives up after half a second. Does this make sens???

Any info would be appreciated. Thanks

 

[Fordkoppie]

Thanks Rick. So I guess one should check the level while it's running and then fill it up to about 25mm from the top??

:nonono::nono:
It should be on that 25mm level from top when it is OFF

 

[Nic_s]

Thanks Rick. So I guess one should check the level while it's running and then fill it up to about 25mm from the top??

:nonono::nono:
It should be on that 25mm level from top when it is OFF

So I should make sure it's right first thing in the morning before starting it??

 

[Fordkoppie]

Yes - Otherwise it would just spill everything once you kill the engine if you filled it while running

 

[rick540]

Yes - Otherwise it would just spill everything once you kill the engine if you filled it while running

The procedure to check the fluid with the engine and car hot after a long drive. This applies to all the E32/E34 V8 cars and the older E23/28 cars with the H31 braking system. it does NOT apply to any other E32/34 besides the V8 cars. It also has nothing to do with Self levelling suspension as some websites may imply.

1) Turn engine off
2) Pump the brake pedal 10 -20 times till it becomes firm and hard to press
3) Check the fluid level it should just be visible on the metal seive in the tank (25mm from the top).

If it's cold, you can check it the same way but make the level about 40 mm from the top to allow for fluid expansion when hot.

Jandre can explain to you nicely what happens if you top it off when the car is running like they did with his.

 

[Nic_s]

Thanks guys. Will make sure the level is correct and then drive it for a while and check.

Hopefully that will cure the slight tug it gives the steering wheel from time to time. It did it just now when I went home for lunch. Almost sounds like the aircon pump going on and then off, but the aircon is off and I can feel the tug in the steering wheel. :thinking:

 

[zaleonardz]

If your E34 power steering is not pissing out oil all over the place, it means its not working :biglol:

+1 on the H31 return from the booster, I concur with Rick fully...

 

[rick540]

Thanks guys. Will make sure the level is correct and then drive it for a while and check.

Hopefully that will cure the slight tug it gives the steering wheel from time to time. It did it just now when I went home for lunch. Almost sounds like the aircon pump going on and then off, but the aircon is off and I can feel the tug in the steering wheel. :thinking:

The tug is a slipping belt, maybe check your spring tensioner is sill good.

 

[gnativecs]

Hi all, need some assistance with a power steering pump if anyone can direct me where to get one. This is for E34 540i V8. Thanks you