Power Steering leaking like a sieve

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Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Power Steering leaking like a sieve

Post by Germz »

I've been trying to track the leak that has been progressively getting worse. Yesterday I had someone turn the wheel with the car running while I looked in the engine bay. It appears to be leaking right around the brake booster? Not sure if I'm seeing things correctly. I've been doing some reading and seeing that I could replace the o-ring between the master cylinder and the booster? Is this just as simple as removing the MC, replacing an o-ring, then buttoning everything back up?
Mike W.
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Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: Power Steering leaking like a sieve

Post by Mike W. »

Germz wrote: May 13, 2021 1:12 PM I've been trying to track the leak that has been progressively getting worse. Yesterday I had someone turn the wheel with the car running while I looked in the engine bay. It appears to be leaking right around the brake booster? Not sure if I'm seeing things correctly. I've been doing some reading and seeing that I could replace the o-ring between the master cylinder and the booster? Is this just as simple as removing the MC, replacing an o-ring, then buttoning everything back up?
Yes it sounds like the booster. The O ring in question is inside the booster so you have to remove the master, remove the booster, remove a little screw holding it together making absolutely certain you have it contained somehow, because it is under significant spring pressure which will catch you by surprise and send things flying, change the O ring and reassemble. There are an assortment of other seals in there, but nearly always the big one is the only problem.

I can't stress this part enough, making absolutely certain you have it contained somehow, because it is under significant spring pressure which will catch you by surprise and send things flying.
Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Re: Power Steering leaking like a sieve

Post by Germz »

Mike W. wrote: May 13, 2021 3:50 PM
Germz wrote: May 13, 2021 1:12 PM I've been trying to track the leak that has been progressively getting worse. Yesterday I had someone turn the wheel with the car running while I looked in the engine bay. It appears to be leaking right around the brake booster? Not sure if I'm seeing things correctly. I've been doing some reading and seeing that I could replace the o-ring between the master cylinder and the booster? Is this just as simple as removing the MC, replacing an o-ring, then buttoning everything back up?
Yes it sounds like the booster. The O ring in question is inside the booster so you have to remove the master, remove the booster, remove a little screw holding it together making absolutely certain you have it contained somehow, because it is under significant spring pressure which will catch you by surprise and send things flying, change the O ring and reassemble. There are an assortment of other seals in there, but nearly always the big one is the only problem.

I can't stress this part enough, making absolutely certain you have it contained somehow, because it is under significant spring pressure which will catch you by surprise and send things flying.
Okay thanks for confirming what I had expected. Is this procedure spelled out in the Bentley? I haven't taken a look yet. Also, I'm assuming this can't be done while on the car?
Mike W.
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Joined: Feb 12, 2006 12:00 PM
Location: California Whine Country

Re: Power Steering leaking like a sieve

Post by Mike W. »

Germz wrote: May 14, 2021 11:35 AM

Okay thanks for confirming what I had expected. Is this procedure spelled out in the Bentley?
I doubt it, but I've never used the Bentley.
I haven't taken a look yet. Also, I'm assuming this can't be done while on the car?
Correct, it has to be removed. It might be possible to do it with the M/C still on, I did and then crossthreaded the bolts going into the booster. Fortunately I had a spare I then rebuilt and installed after I removed the M/C.
Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Re: Power Steering leaking like a sieve

Post by Germz »

Mike W. wrote: May 14, 2021 12:54 PM
Germz wrote: May 14, 2021 11:35 AM

Okay thanks for confirming what I had expected. Is this procedure spelled out in the Bentley?
I doubt it, but I've never used the Bentley.
I haven't taken a look yet. Also, I'm assuming this can't be done while on the car?
Correct, it has to be removed. It might be possible to do it with the M/C still on, I did and then crossthreaded the bolts going into the booster. Fortunately I had a spare I then rebuilt and installed after I removed the M/C.
Okay thanks! I did see through some other threads that I'm looking for the 3x38 o-ring. I'm guessing that this should be pretty obvious once I get everything taken apart. I'll be attempting this weekend!
tn535i
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Location: Middle Tennessee

Re: Power Steering leaking like a sieve

Post by tn535i »

Make sure you read up on some of the watch outs, like polishing the internal bore where the grub screw penetrates before putting it back together, or it may ruin your new o-ring.

I think I still have some of those O-rings and would not mind sending you a couple as you can put them in a small envelope and do that for the price of a stamp. Just PM your address to me and I don't mind, if you don't mind waiting for US Mail.
Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Re: Power Steering leaking like a sieve

Post by Germz »

tn535i wrote: May 14, 2021 2:29 PM Make sure you read up on some of the watch outs, like polishing the internal bore where the grub screw penetrates before putting it back together, or it may ruin your new o-ring.

I think I still have some of those O-rings and would not mind sending you a couple as you can put them in a small envelope and do that for the price of a stamp. Just PM your address to me and I don't mind, if you don't mind waiting for US Mail.
Honestly that would be great, I will PM you shortly!
Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Re: Power Steering leaking like a sieve

Post by Germz »

Thank you very much to tn535i for the o rings! After a lot of frustration and a couple kinked PS lines, i got the o ring replaced. Everything went back together smoothly.

Until today. I noticed some fluid on the floor so i had a buddy get in the car with it running and turn the wheel full lock to full lock. I could see a little spray coming from somewhere every time it got close to full lock. So i stuck my hand in there and it appears to be coming from the under side of the master cylinder.

I’m assuming i messed something up since PS fluid shouldn’t be up there. Should i try replacing the o ring again?
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Power Steering leaking like a sieve

Post by tn535i »

Not sure what to suggest except start by cleaning everything really well and be certain where it's leaking. You say it is spraying? I wouldn't think the booster low pressure return chamber would in any way spray fluid, just dribble out. Normally you get a good seal with a new o-ring IF it was in no way damaged on install and the parts it mates to were also cleaned, solving the booster leaking. But pressure switches and maybe hoses/connections are also know to leak and it's possibly something else.

If it is the booster I would guess (because I know it's been discussed) the grub screw on the bottom that penetrates the bore inside the booster, left some rough edges and the new o-ring slide across that and was damaged.

I do not know for sure if you can safely remove the grub screw once the master is re-attached or if something inside the booster will move? If that is safe removing the grub screw would verify if the leak is only from that space between the master cylinder and booster.

At least if you have to get back into it you have some experience now. If there is a high pressure leak on the booster overwhelming the return chamber seal or something like that I thought there was someone here (if still around) that rebuilt the whole booster.
Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Re: Power Steering leaking like a sieve

Post by Germz »

I could try doing it again like you said.

Do you think that the fact that it comes out more at full lock that that has any indication of anything? Basically I’m wondering if the booster itself is bad, like you mentioned.
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Power Steering leaking like a sieve

Post by tn535i »

Are you saying it leaks all the time and just more at full lock? Not sure ?

At full lock (which you should avoid) the spool valve is basically sending full pump pressure to 'help' turn the wheel. It is useless to apply 'more' steering input unless your goal is to break your steering gearbox mount. Hint: I think this driver behavior (past or present) is what breaks the mount on e28's not a relatively weak design. Sure it is 'weaker' than some other R&P designs but not fragile.

So... What I believe happens in the system at full lock is less or at least vey little recirculation of fluid from the steering box since the spool valve is trying to send all flow to move the wheels (which can't) it is dead headed (more or less). This results in the system pressure trying to go up and now relief valves inside the pump and on the regulator need to open. Normally ATF just passes through the spool valve and recirculates back to the reservoir and the systems is at enough pressure that it keeps the booster happy. Maybe at full lock the relief valve in the regulator also has to open wide and go to work. There are hoses that return fluid to the reservoir from both the brake booster and the regulator and perhaps one of those is leaking when the return flow jumps up, the one from the regulator is pretty small I think and that is the one I would look at. Maybe it is spraying on the booster ?

It does not make much sense to me the booster starts leaking worse when the pressure goes up at full lock, unless there is more of an issue than just a leaking fluid return chamber (the o-ring you replaced). That chamber is at low pressure as it is basically 'vented' to the reservoir.
Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Re: Power Steering leaking like a sieve

Post by Germz »

I’m not positive if it leaks all the time, i don’t think so. I believe it just leaks while turning, more the further i turn the wheels the more it leaks. And when i turn the wheels it’s like a visible leak, it’s slightly better than before i did the o ring but not fixed. I’m just now trying to decide if i want to try the o ring fix again, or just get another booster all together.
demetk
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Location: CT, USA

Re: Power Steering leaking like a sieve

Post by demetk »

Germz wrote: Jun 11, 2021 2:53 PM or just get another booster all together.
Or go the vacuum booster route.
Germz
Posts: 309
Joined: Jan 22, 2014 3:01 PM
Location: San Diego

Re: Power Steering leaking like a sieve

Post by Germz »

Just wanted to post an update. First off, thanks again to tn535i for sending out those O-rings for the booster.

After I fixed the booster, I spotted another leak and I couldn't find where it was coming from. Finally I was able to get a hand from someone and spot where it was coming from. The high pressure line from the steering box to the regulator (?) had a little pin hole that you couldn't see or feel when the car was off. I replaced that line, and a few of the low pressure lines while the system was drained, and now no more leaks!
tn535i
Posts: 5585
Joined: Jul 14, 2006 1:30 PM
Location: Middle Tennessee

Re: Power Steering leaking like a sieve

Post by tn535i »

Glad you found the problem. I've never had to replace any of the high pressure hoses, yet, but...

Now you've cursed us by reporting another potential issue. I'm sure my 535 will develop that same leak any day now :roll:
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