91 750il Steering Box leak

[Jormotors]

I recently purchased a 91 750il with 70,000 miles. It has a pretty large power steering leak in which seems to be coming from the steering box itself. All the lines above are very clean and i cant seem to find any leaks except from the bottom of the box.Is there a fix for this? Can these units be resealed or rebuilt?

I tried tightening up anything i could but as seen in the photos there is a steady drip from bottom seem onto the electronic connector, Top of the steering box is 100% clean so do not think there is any hose leak.

Thanks for any info.

45931450381_337a949ff1_k by kamotors@y, on Flickr


45931450781_1748567ac0_k by kamotors@y, on Flickr

[shogun]

Usually the leak comes from the power steering lines and the banjo bolts, check these first, difficult to see from top. you have to remove the heat protection shield above the steering gear box on left side and then you see the hoses with the banjo bolts. Then it runs down outside on the steering box and drops down. The hoses usually leak at the crimped ends. Here we made pics long time ago http://www.bimmerboard.com/forums/posts/124919
http://www.realoem.com/bmw/enUS/show...diagId=32_0271
hydraulic hoses you can buy online or find a shop which replaces the rubber hoses and crimps the parts new.

For the steering gear itself I have some sets on stock, here pics from our repair http://www.bimmerboard.com/forums/posts/841421/


In case that leak comes really from the power steering, then you have the wrong power steering fluid. 750 iL 1991 needs Pentosin CHF 11S and that is green, that looks like ATF red fluid

Clean everything and then find the point where it starts, my bet is the 2 hoses to/from steering gear on top, banjo bolts, seal under banjo bolts. I also have seenn cracked banjo blots when people tighten the banjo bolts too much.
see last pic http://www.bimmerboard.com/forums/posts/124919

[Jormotors]

Usually the leak comes from the power steering lines and the banjo bolts, check these first, difficult to see from top. you have to remove the heat protection shield above the steering gear box on left side and then you see the hoses with the banjo bolts. Then it runs down outside on the steering box and drops down. The hoses usually leak at the crimped ends. Here we made pics long time ago http://www.bimmerboard.com/forums/posts/124919
http://www.realoem.com/bmw/enUS/show...diagId=32_0271
hydraulic hoses you can buy online or find a shop which replaces the rubber hoses and crimps the parts new.

For the steering gear itself I have some sets on stock, here pics from our repair http://www.bimmerboard.com/forums/posts/841421/


In case that leak comes really from the power steering, then you have the wrong power steering fluid. 750 iL 1991 needs Pentosin CHF 11S and that is green, that looks like ATF red fluid

Clean everything and then find the point where it starts, my bet is the 2 hoses to/from steering gear on top, banjo bolts, seal under banjo bolts. I also have seenn cracked banjo blots when people tighten the banjo bolts too much.
see last pic http://www.bimmerboard.com/forums/posts/124919

Thanks so much, i saw the heat shield and didn’t know if there was anything to check under it, I’ll check those first. As for the red ATF, the previous owner switched it over. Will ATF really cause damage even unmixed? If so I’ll definitley drain and switch it back.

[shogun]

The owners manual specifies Pentosin for the 750iL with self levelling shocks. It is said that other fluid will/might damage the seals of the SLS shocks and they start to leak. Instead of Pentosin you could also use the equivalent green power steering fluid from Febi Bilstein, they have mineral based fluid for Pentosin CHF 7.1 and synthetic for Pentosin CHF 11S. Also never mix Pentosin 7.1 and 11S, as mentioned on all the Pentosin cans, could in worst cade cause clogging.

In case the shocks look at the bottom, here is the fix http://www.bimmerboard.com/forums/posts/779720/ http://www.bimmerboard.com/forums/posts/831490/

Here is a post where someone fixed the leaks with AW32 and put in Lucas Booster Stop Leak about 20% ratio http://www.bimmerboard.com/forums/posts/694831

[Jormotors]

I got the heat shield out of the way and the banjo bolts/hoses are good. I can run my finger all around them and get no residu back. I made sure they were snug. Looks like it’s the o-ring actually inside the box. I’ll try stop leak first and see how that goes.

[shogun]

We had such a problem some years ago on a 750 steering gear box. The housing was leaking. Used a seal kit and disassembled/assembled to gear with the new seal kit. Installed it, again leaking. Pulled it out again, resealed it, checked the surfaces of the contacting parts, installed it again, still leaking.
Third time same procedure, then we used besides the o-ring on the contact surfaces of the housing a thin film of liquid seal, that works now since some years without leak.

[Jormotors]

Good to know thanks. Is there any write ups on best way to remove steering box? Doesn’t look like there is much room to work with

[shogun]

on the website of my wrenching buddy, our special technic with twisting and turning the gear box, without removing the cross member: how-to-take out steering-gearbox http://e32b12.blogspot.com/2012/09/h...g-gearbox.html
It is tight. but doable.

cpl. thread http://www.bimmerboard.com/forums/posts/1118050