E39 power steering whine solved in detail - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 08-05-2011, 10:09 PM
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E39 power steering whine solved in detail

Right, after a lot of online looking at what this noise could be, everything pointed to a fluid flush, or air in the system.

A little history on the problem first.

I have owned the car two months now, it is an 02 E39 525i Msport 155k miles.

From the day I picked it up it had that horrid whirring noise coming from the belt area.
Because the Idlers and belts where due a service, I changed them out with the new revised hydro tensioner, and the additional idler which bolts to the alternator bracket. It was then about 5% quieter, and still driving me mad.

For anyone wondering what it was that was driving me insane, it was a whirring noise coming from the belt/power steering pump area. This noise was constant, even with the wheels straight ahead, and the pump by-passing. It got far louder while you were turning wheel in any direction.

On inspecting the fluid it was pretty bad, so I changed it out for some uber fluid. Flushing the entire system at the time made no difference either.

For days I thought there was still air in there, so I opened all connections EVERYWHERE to see if I could get it out. No luck, it all seemed ok.

Off with the belt to try and see could I feel the pump rough by turning it with my hand, no noticeable roughness, how strange....

For fun, I called to the dealers to ask the parts guy if pumps where a common wear item. I got the usual ''They never go'' ......but, he did say a new one was around 700euro or something. No thanks, Id rather make one myself. He then said that a place near me reconditioned PS pumps....interesting I thought....what exactly could go in them....not much in there.

I then decided to pull off the pump, and tear it down, I had nothing to loose really.
For anyone not into tech stuff, or not into engineering, then search ''Sliding vane pump'' its the type of pump used in many PS systems. For anyone that is an Engineer, then you will know all about them. I say that, because I know a LOT of Engineers with E39s - Best car in the world right!

Given that I have the car just two months, I didnt really know its history. But, It does have a full service history, each service bill in the region of 800euro - this woman minded her car and replaced anything it needed before time. The power steering pipes to tank were damp as they do sometimes be, and the clips and hose had been replaced with proper clips, and the hoses cut back. So, basically what Im getting at, is that I dont think it ever ran low on fluid, at least not low enough to starve pump dry. This bit is important for my diagnosis later.
By the way, Incase you dont know by now, I tend to keep looking at stuff until Im happy with why it failed. I cant really accept that It did, and carry on.

So, onto the pump teardown, Its easy remove as you know, 3 13mm bolts, a 10mm bolt holding a pipe clip, and of course the pipes and belt need removing. Its a 15min job to have it out in your hand.


Im going to assume for the next bit that you may or may not want to open your pump for fear of messing it up. Thats fine - but, that doesn't phase me one bit, Im used of this kinda stuff, seeing how it was built/designing similar things/and so on.

The pump below, with the metal brackets removed,



Rear removed(4 torx bolts)



And here lies the fault, the internal wall where the vanes run is damaged heavily as you can see, this should be very smooth, with no steps or ridges, and symmetrically oval shaped for want of a better word/calling,



A few close-ups of damage,









Not pretty is it.....you can now see how a shocking clicking/whirring noise can originate from the pump given that the vanes are passing over these ridges at high speed,






Conclusion:

On inspecting all this closely, I knew right away that it had all the signs of the classic vane pump cavitation.

Cavitation in this case is caused by a partial vacuum forming on the intake side of pump.
You can read up on cavitation in depth if you wish, Im not going into too much detail here, as I feel there is no point, its a vast subject which would require a post all of its own.
But, having said that, I need to explain it a small bit so you'll understand why it happened in this case.

First off, this pump was not worn by it ever running dry.
It was something different that caused the wear.

If you know about vane pumps, you know how they work, if not, get reading.

The problem in this case is pretty simple. If there is a partial vacuum on the intake side then the vanes cannot slide out of rotor to conform to the internal wall. Once this vacuum is relieved behind the vanes(slot pockets) they shoot out and hammer into the wall at high speed. The areas where the most wear took place indicates even more that this is the case.

Now....the vacuum on the intake side, what caused that I hear you ask....simple.....the filter in the PS fluid tank.
One thing I hate in all systems, is any type of filter that is contained within the holding tank. Simply because it means that it is either forgotten about, not even known about, or not replaceable at all in my case.

And guess what....my filter was rotten dirty. As you may know, it is screwed down with a small torx screw. I removed this, and also removed tank from car. With the filter free inside the tank(its too big to come out) You can then fill the tank with some Jizer or whatever, and give it a good shake. Repeat a few times until solvent runs clear.
Keep in mind that the oil will also be thicker in lower temperatures, which in turn will make it even harder for it to pass through a blocked filter.

The cavitation was so bad in my case, that it was actually aerating the fluid on re-entering the tank. These small bubbles could clearly be seen after a run. But, I did think at the time I just had some trapped air in there that was being constantly recirculated.

The filter is now minty fresh, and screwed back in. I have to admit, I did think about cutting holes in it for peace of mind. Its simply too fine a mesh from the factory. I hear you say, that thats madness, but, you have to ask yourself whats better, a blocked filter that causes cavitation that kills the pump. Or, some slight contaminants in the oil that also may kill pump. Given that the pump is fairly robust, and could handle small particles, you have to ask yourself which is the better route? In this case, it seems that they should have gone with a bigger mesh filter Im afraid.

As for the black sludge in the filter.....where is that from....again, easy, but not too obvious at first, its from the interior bores of all the rubber pipes.
Perhaps the rubber was of poor quality, or the fluid not 100% compatible with that particular rubber.

Amazing all the stuff you need to add up to conclude a failure for said part down the line.

You could say that maintenance may have prevented this. Maybe, maybe not...
A fluid change would have done damn all for the filter.
A filter change is not possible without renewing tank.
A filter clean to my knowledge is not wrote down by BMW as part of any service.
Hoses should last forever if they are matched with whats flowing through them.

So....it brings us back to the fine-ness of the mesh in the filter, or if they should have just run without - the pump is dead now anyway with it as mentioned above.

Now.....enough of that.....conclusion has been found, I now had a car with no PS pump!! A new one may as well be a million Euro, and my recon guys were on holidays for three weeks. Actually, a quick word on a recon, I suspect they refit the worn ring with a new one, and perhaps new vanes and bearing. I really, really doubt they are re gringing the internal wall. Its just too complex a geometry I feel to bother with, but, maybe they do...I wouldn't, you gone way into the ideal case hardening at that point.

!!**********The next bit is for the fabrication die-hards that hate spending money, proceed with caution*************!!

So, a quick look around the 'spares' bin, and guess what..... A mk3 Golf PS pump is more or less IDENTICAL to the BMW Item!!!!!!!!!!!!
The chassis of the pump is the same bar one bolt hole with does not exist on the Vw pump. There is still 5 m8 bolts holding it on to the metal main bracket, so Im more than happy with that and I would also be happy if it was to do with an aeroplane I was sitting in. Take my word on this, its perfectly fine to run on there.
So, this now means that you have a ton more scrap yard pumps to choose from as the Mk3 Golf PS pump is very plentiful, and I suspect, about half the price.
Fittings are also the same and nothing needs to be changed.

There is one small catch though and that is the pulley offset.
This is a simple thing to get around though depending what you do, or who you know, or where you work. It involves 15min on a lathe and 2 euros of aluminium. Cheap, compared to a new pump...or a second hand one you may not be able to find!

The Vw pump pulley flange face sits 14mm farther out than the Bmw one. The Vw shaft is 14mm longer if you like. The pump casing is the very same bar one bolt hole as I said above. Also, the Vw pumps are cast iron bodied, the Bmw item is Lm25 aluminium alloy.

Ideally if I had it(Billet, or time to cast), I would have made a complete billet, or cast Alloy pulley. But what I did instead was fine too, and you could do the same if you wish.

Below is a rough drawing of where you re-gain the 14mm offset. All other measurements are not important, just fill them in as you go/measure vw pump flange diameter.



And a few bad pictures of starting to make it, and of it fitted, didnt have time to take some along the way,







I plan on casting a one piece all alloy pulley for it next month, hopefully... Its fine as is, but the plastic pulleys can be bad at the best of times.

So, thats it really, the last bit may never be carried out by anyone, but, its an option, and an easy one if your near a lathe, considering how plentiful Vw pumps are, and the fact they bolt right up.


To conclude everything.....

The Filter is the main problem I feel. Its just too fine to let the lesser threatening crud through. The crud comes from the interior bores of the rubber hoses. They may be to just poor quality hoses, or, Incorrect/incompatible fluid being used at sometime.

I know a lot of places say to replace the hose. This is no good on its own, since filter needs cleaning too.
And...If your pump is whining, its too late at that point as you can see above.
As for the Vw pump, its running just ace, I can now hear just the injectors opening as you should on the I6 engines. All whirring is gone. Steering feels way better, and the pump internal volumes are very near the same also.

All fluid aeration is gone.

I probably wont change any of the hoses to be honest. Theres new and correct fluid in there now that I can be sure of. I may or may not bin the filter at a later date though....at my own risk of course

Hope this might help or enlighten even one person at least, if it does then even at that, it was worth typing. The Vw pump bit may save a few pound too, and something to show to the techs in Bmw perhaps the next time your in!

Take care,

Brian Garvey.
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#2 (permalink) Old 08-05-2011, 10:20 PM
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Very nice; thanks for sharing!

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#3 (permalink) Old 08-06-2011, 09:20 AM
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Excellent "How To" guide, fella ;-)


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#4 (permalink) Old 08-06-2011, 02:36 PM
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There will be loads more Im sure.

Must throw up a few pictures in the intro section too,

Talk soon,

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#5 (permalink) Old 08-08-2011, 05:45 PM
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Nice Writeup. Thanks.

My steering is a little jerky. The mechanic says he does not know what is wrong, but I'm going to go in your direction. Just change the reservoir, new lines and flush.
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#6 (permalink) Old 08-09-2011, 06:38 AM
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What a great write up.

One question though, how if the filter put into the tank in the first place?


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#7 (permalink) Old 08-12-2011, 11:53 AM
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Quote:
Originally Posted by brettski View Post
What a great write up.

One question though, how if the filter put into the tank in the first place?
The tank is made in two sections, its either bonded, or ultrasonically welded together once the filter is placed inside.
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