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Old 02-08-2011, 05:50 AM   #1
bcaway
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Default 993 steering rack DIY rebuild tutorial

After taking my 1995 993 for a 300km drive the other day nearing home I had to stop due to the power steering pump whining. The reservoir was low on oil, I bought some ATF and topped it up which fixed the noise. When I returned I discovered fluid leaking from both ends of the rack out of the rubber boots, they were full of red atf!

After finding out the cost of a rebuild in New Zealand ($1500+) and the price of a new one is just plain stupid. I decided to rebuild it myself. Which was a 100% success. with a total cost of just over $100 and a few hours of my time.

I thought I would document this for future DIY'ers.

PLEASE NOTE: This is a right hand drive rack however the procedure will be almost identical for a LHD rack.

This was relativity simple and straightforward with no special tools required:
I welcome any feedback and corrections and thanks to jon928se for his initial advise on dis-assembly techniques.

First I sourced the 993 Rack Seal Kit from http://www.klaindustries.net/ $69 + shipping
Click the image to open in full size.

It turns out the US kit (LHD) is slightly different to my RHD rack. They were very helpful and promptly sent me 4 square ring seals that were about 10mm bigger diameter to fit my input shaft at no extra cost! (nice guys!)

I have broken these DIY instructions into steps (each with its own large image that I am linking to to save huge images in this thread):

STEP 1 REMOVAL http://www.webbnet.com/911/images/99...rack_STEP1.jpg

STEP 2 DIS-ASSEMBLY http://www.webbnet.com/911/images/99...rack_STEP2.jpg

STEP 3 DIS-ASSEMBLY CONTINUED http://www.webbnet.com/911/images/99...rack_STEP3.jpg

STEP 4 SEAL REPLACEMENT http://www.webbnet.com/911/images/99...rack_STEP4.jpg

STEP 5 SEAL REPLACEMENT CONTINUED http://www.webbnet.com/911/images/99...rack_STEP5.jpg

STEP 6 SEAL REPLACEMENT FINAL STEP http://www.webbnet.com/911/images/99...rack_STEP6.jpg

STEP 7 RE-ASSEMBLY http://www.webbnet.com/911/images/99...rack_STEP7.jpg

STEP 8 INSTALLATION (coming soon later this week)


Cheers
Brian
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Old 02-08-2011, 05:53 PM   #2
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Great pictures,

In stage 3, the diagram that you show removing the C-clip, have you put a dent in the inner edge (at around 5 O'clock) as a result of inserting screwdrivers into the groove to remove the C-clip? If you have, for someone-else trying this in the future perhaps making a hollow c shaped cylinder (ie an incomplete cylinder if you get what I mean) formed from a steel sheet and rotating it once the end of the clip is lifted into the cylinder may avoid nicking that part of the rack?
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Old 02-08-2011, 06:14 PM   #3
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Hi RS man,
RE: c-clip removal, the u shape is part of the factory rack housing and is there to enable you to get the screwdriver behind the clip initially also this part of the rack has no seal surface and is external to the unit only covered by the rubber boot, so scratching is not a concern.

Yes we also thought of making a sheetmetal (1/2 circle) to slide down behind the screwdrivers as we worked our way around, this would have minimized our frustration when slipping and the clip pinging back into the groove - but with a few tries we got it out just fine.

Another question was what oil did I use. I read somewhere (and will locate it before my final assembly post) that certain types of ATF are fine. Since proper Porsche oils are not available in my town, I used Valvoline DX-3 ATF. I will include the proper refilling procedure too - at the end.
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Old 02-08-2011, 07:53 PM   #4
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Step 4,5 and 6 added today, I don't have an exploded view so I have made up names for some of the parts
If anyone has or can get an exploded view that would be a helpful addition to this DIY

STEP 4 SEAL REPLACEMENT http://www.webbnet.com/911/images/99...rack_STEP4.jpg
STEP 5 SEAL REPLACEMENT CONTINUED http://www.webbnet.com/911/images/99...rack_STEP5.jpg
STEP 6 SEAL REPLACEMENT FINAL STEP http://www.webbnet.com/911/images/99...rack_STEP6.jpg

final assembly con installation coming soon\~
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Old 02-09-2011, 05:11 PM   #5
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Rack assembly posted:

STEP 7 RE-ASSEMBLY http://www.webbnet.com/911/images/99...rack_STEP7.jpg

installation coming soon.
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Old 06-07-2011, 05:27 AM   #6
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Hey Brian,

Greetings from Malaysia! Great great post, and at an opportune time too! My rack developed a leak and your write up gave me a reason and the roadmap to do it myself. One little tip, that great big C -clip that's in the rack retaining the collar? I just used an allen key (2.0mm) , levered the clip with a screwdriver away from it's notch then used the allen key to hook it out. I got the clip out in one go and by myself with out another pair of hands

I've run into a small problem though and have pm'd you. Would appreciate your insight if possible!

cheers,
Kris
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Old 08-23-2011, 06:50 PM   #7
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Great writing !!!!!

For LHD it needs some adptation as you mentionned, for example for input shaft (this one gave me some hard time !! ).

Now I'm in step 7 and so hope everything will be fine when I'll crank the engine.

One thing I'm still wondering, and this makes me quite confused as I'm mechanical engineer, is how this whole stupid unit is working ????
I can't see on the input shaft some radius hole postions that could affect the fluid flow...
I'm used to understand things once I get them appart, but I've found this exception

Any suggestions ?
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Old 08-23-2011, 09:58 PM   #8
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I didn't even try to figure out how the thing worked But thanks to Brian with his detailed write up and walk through the rebuild via mail I fixed my leaking and am happy to report she's not only leak free now but the steering is a just a tad lighter and with a bit more feel . I did run into some probs as follows :-

1. At step 3 I used a small allen key to 'hook' that big circlip out whilst maneuvering it out of it's slot with a thin blade screw driver.

2. At steps 4 and 5 where we are to try and drift the oil seals out from the steel retainer and rack respectively, my seals were stuck solid no matter how hard I tried. I ended up using a drift with a C-Clamp and by tightening the Clamp down, pushed the seals out. It was dead easy that way.

Thanks again for the write up and walk through Brian!

cheers,
Kris
'97 993 TT
'05 645 Ci
'02 X5 - Dog mobile
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Old 08-24-2011, 06:22 PM   #9
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Hi Elonash,
Sorry cant help with the fluid dynamics, It was challenging enough to keep everything in order, replace the exact same seals and reassemble. I didn't even think about how it worked. I'll leave that up to the german engineers, after all im just a simple DIY'r.

Cheers
Brian

P.s. sorry I have lagged on the final assembly. Anyone need help with that I'll get the photos up, or PM me.
My only installation quick tip is to hang the rack (loosely) and hook up the lines, then start the engine very briefly several times while topping up the reservoir and DONT steer initially, check for leaks too. Once the fluid level remains the same in the res, then steer a little (BE careful not to hit the stops as the rack is not hooked up). If no leaks install completely. Road test and top up fluid as required.
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Old 08-24-2011, 11:25 PM   #10
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One important note for anyone with RHD cars who wish to tackle this. The RHD drive cars have a different set of seals for the worm gear assembly area. Apparently that part on the RHD cars are a 928 part (I can't confirm this only repeating what I was told). The important bit is the LHD seals don't fit here. I had my rack stripped down in my garage with the wrong seals in my hands. It took another 10 days for the right seals to arrive. If you don't want to go through what I went through make it VERY VERY clear to the guys at KLA industries that you have a RHD car and that you know that RHD cars have a different set of seals. They know of this, and they make a great quality kit BUT as they deal with predominantly North American LHD drive cars they ship these out on autopilot....

cheers,
Kris
'97 993 TT
'05 645 Ci
'02 X5 - Dog mobile
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Old 08-25-2011, 09:01 AM   #11
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Thanks Brian for your tip !!

Actually my point now before re assembly of the input shaft casing is: is there any relation between the linear position of the main shaft and the radius position of the input shaft ?
I would answer no to that question but thus how this thing works....?
I feel that I should just install the input shaft without considering the linear position of the main shaft (indeed this is what I've done yesterday).
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Old 09-29-2011, 03:26 PM   #12
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OK, so...
As I finished the rebuild of my rack, I realize it was hardly movable by hand (I remember when I got the rack out of the car it was easy to turn it by hand) but I figured it was the quantity of news seals that make the movement no more possible without the help of the pump...
I was wrong
The pump is not more able to move it than me...
The rack only move because I apply a real torque on the steering wheel... to draw you the picture the steering weel doesn't come back to neutral after a corner!!!!!
So the car is not driveable...I need to take it appart again but I have no clue what I did wrong...

Any ideas ?
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Old 09-29-2011, 09:53 PM   #13
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Elon, if you look at the step 2 page in Brians posted pics there is a threaded cap which has to be removed and a piston pulled out with needle nosed pliers. After which out comes a 'white plastic part'. That's a slipper that preloads the rack to reduce backlash on the rack/worm gear. The preload has to be set just right such that you have 'slop' but not too tight that the rack is now pushed hard into the worm gear. Brian had advocated marking the 'exact' depth and location of the threaded cap prior to removal to ensure that at the very least you will have a preload identical prior to dismantling. It is possible you've cranked this cap on too tight and need to back it off. Get the car up safely, back it off, test the steering wheel. You should get it to the point where with the wheels of the ground the steering wheel turns light and easy and just before the point you notice some slack. Drive her, then tighten or back as the case maybe. Sorry I cant be specific with values but the factory manual has no numbers here as they never intended for the rack to be rebuilt. If someone can jump in with some numbers it would be a big help!

cheers,
Kris
'97 993 TT
'05 645 Ci
'02 X5 - Dog mobile
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Old 09-30-2011, 05:42 AM   #14
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Krish,

Thanks for this suggestion. I remember that I (tried to) respected carefully to screw it back at the same position (I have punch holes all around plus color marks and I also check the depth with the thread surface.
Even if I replaced it well what I noticed is it was a hell to screw it enough. Actually so hard that I damaged the hex shape of the threaded cap when screwing and I needed to put the cap in the freezer to make it possible.
Did I add one turn more ????? arghh...I can't believe this, but it would be a nice explanation...
Will keep you updated !!!
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Old 09-30-2011, 11:01 PM   #15
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Could be you just turned it just that one turn extra . At least lets hope so or you're looking at taking the rack apart to check. It was a b*tch for me to open as well, that threaded cap. That edge 'punch' that locks it in place being the culprit if I recall.

If backing it off doesn't work, you might want to take that cap off first before dismantling the rack to check and confirm that pre load spring is properly seated in it's recesses.

Did you grease the rack and pinion gears before re assembly?

cheers,
Kris
'97 993 TT
'05 645 Ci
'02 X5 - Dog mobile
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Old 09-30-2011, 11:01 PM
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