850 power steering

[bsifford]

I've been adding Pentosin to my '92 850 as needed when I hear some squealing, but want to address the leak.

To confirm something I think I already know...there is booster shared by the brakes and power steering where there is an O ring that deteriorates over time? This is a common source of the leaks? I've had two 850s where I know this was rebuilt with my first 850, but need to check my maintenance file for the current 850.

When checking the power steering reservoir...need to get it up to specific temperature? There is a screen I pour the Pentosin thru, but how do I know not to overfill?

Feeling very ignorant right now and I've tried searching for the answer, but I'd rather ask than run my car doing damage when I am sure for other more experienced 8 owners this is a no brainer question.

Thanks

[Larkin660]

Mine basically does the same, add fluid as needed.

The booster you're referring to is called the "brake bomb" you can look up various threads about it on here.

I've been putting off doing mine for a few months now

[Larkin660]

Also to check it, pump the brakes about 20 times until they get hard with the car turned off, this depressurizes the system, then just check the fluid as you normally would.

If the brakes get hard after 5 or so pumps the bomb is bad

[Wuffer]

Sorry, I disagree with the "20 times" recommendation to check fluid level. To check Pentosin (Hydraulic fluid) correctly, you must depressurize the system fully by pumping the brakes, ignition off, Pentosin reservoir cap off, until the fluid stops rising then fill to approx 1/4 - 1/2" from the top of the reservoir. With the hood open, and appropriate positioning you can watch the reservoir while pumping the brake pedal. Brake pedal will go thru a couple of levels of hardness while pumping but to check for correct fluid level, pump til fluid stops rising. If overfilled, remove some with a turkey baster (dont tell your wife) and keep pumping/removing til fluid stops rising. My (not so) humble opinion....

[legoman67]

you havent owned an 8 until you have had a fountain of pentosin out of your reservoir... i made a mess the first time i did mine... lol

[Fatandre]

Would you say its normal that the power steering pump fails?

[Craig540i]

These cars are now between 15 and 25 years old. Realistically it's quite normal for anything to have worn out / failed by now. Having said that they are lot better built than most current models, which I doubt will last 10 years....

[henryc]

I agree with Wuffer- this is the way to check fluid level.

[sleepy81]

After dismantling mine I would say the power steering pump is quite a simple construction and robust . The main area of weakness if there is one would be the bypass jamming open bit I've not heard of that happening.

[shogun]

I have re-sealed now about 10 power steering pumps, that are the double vane pumps for the 750 E32 with LAD. Pretty simple to do that. I usually use the repair kit from pskits.com or rennbay, they are universal kits and fit all ps pumps from ZF with a 19mm shaft, various BMW as well as Volvo, Porsche etc. use them. 2 profile rings, O-rings of various sizes and shaft seal, that is basically all.
The pumps do not fail in function, they start leaking. If they run dry or with air inside, there could be metal/metal touching, but even with some marks on it with a new seal kit they will work. Seal kit looks like this, same is used on the Porsche.
944 Power Steering Pump Seal Kit Install https://www.youtube.com/watch?v=bMwACwt4tH8

[TxGR8White]

Would you say its normal that the power steering pump fails?

Nope, the power steering pump NEVER fails... and whoever says so doesn't believe in the Easter Bunny either!

[Fatandre]

I can see where you are going with this, but what I meant was if failure was something we should expect after a certain amount of miles or them failing would be something unusial on the m70 engine.

[Craig540i]

One thing that will definitely extend the life of the pump seals though is replacing the fluid regularly. I think this has something to do with good clean oil helping keep the seals soft, whereas old burn oil tending to harden them.