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944 Steering Rack Reseal
944 Steering Rack Reseal
Rack Resealing
If you're considering what it takes to
fix your Porsche power steering then this is a good
place to start. Its a very good idea that you do some
research because this little job is easily and often underestimated. I know this because I've made every mistake
possible and am therefore somewhat qualified to warn you of
the many pitfalls. The information on this page is NOT
complete - I do not have re-assembly instructions. Those
would require many more hours of work than I have to offer.
Still, you can get a good idea of what is involved by reading
through the disassembly areas that I have here.
At the outset, I should tell you that resealing a rack will be
somewhere between moderately difficult and
I'm-so-pissed-at-this-I'll-just-get-rid-of-the-car. I'm
tempted to tell you it is sooo easy and that all you need is
a little determination but I'm afraid this casual confidence
will get a few of you in over your head and if that happens
you'll be looking to lure me into a dark alley. Please
review these "Ten Things to Know ... "
before you begin stalking me.
=== Ten Things
to Know before Attempting to Reseal Your Steering Rack ===
1) It is moderately difficult to get the rack out of the car
and this provides potential for a fair amount of
exasperation (and it's even worse on the turbos). Even if things go very well, it will take over
an hour just for removal. Another hour (plus) to get the
rack re-installed. Expect to double this time if you
haven't done it before.
2) Unless you have a hydraulic test stand, you'll have to
re-install the rack in order to test for leaks and to
make sure the rack works. If problems arise, you may have to
remove it a second time to correct. This sucketh greatly.
3) Its possible that once you get the rack dis-assembled, you will
find that you need parts, not all parts are included in the
reseal kits. In fact, the one part that is most easily broken
(during dis-assembly) is not included in the kit at all.
ZF, (a German company with a long name)
makes the rack and pump for our cars. They do not make the reseal kits.
The kits are made by a company in Indiana. Their catalog is available on the
internet, see www.transtec.com but to order, you will need to call them. Its
best to order from them directly as re-sellers often re-package the kits to
conveniently hide the fact that kits contain orings that are well past their
shelf life. Kits packaged by Transtec are dated.
ZF will not deal with anyone other than Porsche dealers for mini-parts. This
means that your source for parts is very limited.
4) The new seals are delicate and can be easily damaged
during installation, ordering replacements will
postpone re-assembly.
5) Some tools are needed, a clean place to work, a way to
clean up the rack and parts, some sort of vice, and a
variety of sockets, extensions and tools to replace the
seals.
6) Some machine work is needed to polish the main shaft. If
the main shaft is not defect free, your reseal will probably
last about a month.
7) It is easy to make mistakes in inspecting/reassembling
the rack. Mistakes cost time and money.
8) There is a chance that you will need to have the steering
re-aligned after reinstalling the rack. There is a
very good chance that your steering wheel will not be
centered and will require an additional adjustment.
9) With so many law suits over the past few years, it is
difficult to find people willing to refit hydraulic
hoses. Any parts purchased from the dealer will be very
expensive.
10) Steering racks are a relatively simple mechanism but one
which relies on hydraulic pressure. Many
"reseals" fail because problems with particulate
contamination are not corrected. This is one reason
that even most professionally rebuilt racks are warranted for only 12 months.
Late Note: One exception: Autozone now sells a rebuilt unit that is warranted for life.
=====================================================
This (above) is likely to be what you first see
when you begin looking for the source of your hydraulic
fluid leak. The fluid will probably be coming from one or
both of the boots and may also be coming from the small hole
in the picture. The hole should have a
rubber or plastic dust plug in it (the plug is only intended to keep dust out, not to
keep fluid in). Normally, there should not be fluid in this
cavity.
This hole is here so that when an alignment of the steering
is done, the mechanic can visually confirm that the rack is
centered. In the hole you can see a small dimple (almost
hidden by shadow), the dimple
indicates the rack center point (wheels should be straight
ahead).
Some un-official
nomenclatures.
Introductory Notes:
At the very minimum, the rack and all of
its' components should be completely disassembled,
cleaned and inspected prior to re-assembly. It is likely that the inspection will reveal smaller
problems that contributed to the seal failure. These
should be dealt with.
Other Symptoms:
Aside from leaks, there are other ways
the rack can fail. The most likely is a groaning that occurs
when you first begin to turn the steering wheel. Groaning
can also be caused in two ways; one, by air in the system
(which is usually associated with a leak in the lines
leading to the rack) or a bad seal in
the control tower casting.
Rack Removal
Place the car on jack stands (front only) or ramps.
Disconnect the battery.
Mark the outer tie rod ends (a touch of spray paint).
Pull back the rack boots from the rack (careful, they may be
full of fluid).
Inspect the exposed portion of the main shaft - this will
give you a first indication of a worn or damaged shaft.
Disconnect the outer tie rod ends (use 2 wrenches to loosen
jam nut and then turn the inner tie rod until the rod separates).
Be careful to leave the jam nuts as undisturbed as possible
so to help with minimize mis-adustments to toe-in.
Remove the alternator (OK to leave wiring attached, but get
it clear of its normal location ).
Remove steering shaft coupler bolt. (Use a chisel to
slightly open up the coupler - careful, the racks control
valve is absorbing the blows).
Mark the splined rack shaft (so that the steering wheel can
be correctly re-oriented during installation).
Disconnect the pressure line from the pump & drain.
Loosen the 4 rack mounting bolts (one cannot be completely
separated due to interference from the pressure line).
Separate the steering shaft coupler from the splined rack
shaft.
Disconnect the return line
from its rack fitting.
Lift the rack clear of the suspension cross-member and other
obstructions and begin long-rack dis-assembly.
Long-Rack Dis-assembly
-
Remove the equalizing line (black plastic tubing and
fittings - careful, fittings are brittle and do not usually
come with "kits."
-
Remove the mounting brackets and grommets.
-
Remove the rubber pressure line and the other hard lines.
Drain these. A pipe wrench is a crude tool but will
remove the fitting bolts. Use it only as a last resort.
-
Place the rack in vice, (keep the jaws of the vice on the control
tower casting and away from the pressure
lines) and remove (2) the tie-rods (note:
these are usually very tight; they have right-hand
threads. There is a flange that may have been peened (hammered in
such a way to prevent loosening). Filing or grinding of the
flange may be needed to loosen the tie-rod.
-
Set the boots aside and drain (if needed) and begin Rack
Dis-assembly.
- Mark the tie rods (driver's side and
passenger's side so you will know which goes to which side
of the rack during re-assembly).
Rack Dis-assembly
-
With the rack still in the vice, loosen the collar nut ( right hand
threads). If you're using a hammer
and a drift, take care not to damage the cylinder.
-
Remove the rack from the vice.
-
Separate the rack cylinder.
-
Using a small pick, gently remove the guide ring from the
end of the cylinder. If you forget to remove the guide ring
at this time, the ring will be damaged when the seal is
driven out of the rack cylinder. Your ring will then
look like the one above. Note, the photo shows a damaged guide
ring and the guide pad - both have a lot of dirt embedded
and should be replaced. (These are NOT included in the "reseal kit." Reassembling
the rack without the guide ring WILL cause premature failure
of the seal.
-
 
-
Mark the orientation of the splined shaft to the tower,
getting it back in this orientation is critical to having a
centered steering wheel.
-
Remove the three 10 mm bolts from the top of the control
tower and set it aside.
-
Remove the control tower cover and
seal.
 
-
Grasp the splined end of the control valve and pull gently
(while turning CCW) to remove the control valve & pinion assembly from
the tower. Photo shows the original orientation of bearings
and shims.
-
Remove the (2) 10mm bolts from the bottom of the control tower
casting.
-
Remove the small cover and hidden spring.
-
Extract the guide pad piston, a special tool may be needed.
-
Carefully remove the guide pad from the piston.
-
Separate the main rack from the control tower.
 
Control Tower Dis-assembly
   
-
Place the tower casting in a vice and observe the
installation depth of the roller bearing cap. Gently drive the
pinion bearing and cap out through the bottom of the tower.
Set the bearing aside for cleaning/inspection.
-
Turn the casting over in the vice and access the lower
control valve seal via the pinion bearing hole. Drive
the seal out through the top of the casting.
-
Remove the small rubber plug from the centering pin hole.
Shuttle Dis-assembly
-
Remove the o-ring, nylon ring, & snap ring from the
shuttle cylinder.
-
Drive or press the seal out of the shuttle cylinder. The
seal will be "backed" by a bronze or nylon
guide ring. Observe it's orientation, as one side is rounded
and one side squared.
Main-shaft Dis-assembly
-
Carefully, remove the snap rings, seal ring & o-rings.
These pieces should be removed from the end away from
the rack's teeth. Note how there is an o-ring under the blue
seal ring (this is typical of all seal rings - they must be
supported by an o-ring). Be careful when removing the snap
rings - it cannot be allowed to scratch the shaft.
Inspecting and Polishing The Main-shaft
-
The main-shaft is the most expensive part of the rack. Its'
surface is critical to long seal life. In almost all
cases the shaft should be polished to return it to a
scratch-free condition. Normally, pits cannot be polished
out and will quickly destroy a seal. A skilled
machinist can weld a pitted shaft andthen machine it back to original tolerances.
  
-
Polishing is not something I would attempt by hand. Here, I have
set up a drill press to rotate the shaft. I then simply
use a wet or dry paper (1000 or 1500 grit) to wet-sand small
scratches out of the shaft's surface, finish with
either 2000 grit or buffing compound. A well equipped machinist can do
a much better job for
about $25. The above picture is taken from a flood damaged
car - beware, this sort of thing is frequently sold on EBay.
Cleaning
-
All metallic parts should be cleaned in a mild
solvent (white gas or lacquer thinner). Plastic
(nylon) parts should be cleaned with dish soap,
(stronger solvents will make them brittle).
Other cautions: Many of the fasteners
and parts of the Porsche are cadmium covered as a form of
corrosion control. We tend to want to clean everything
perfectly and many of us have found that a wire wheel
(mounted on a bench grinder) works well for this. For
cadmium covered parts, this is an extremely bad idea.
Cadmium is carcinogenic - it causes cancer. Beware, cadmium
is a life altering substance and can EASILY get into your
bloodstream where it will then damage your kidneys. Kidneys
are extremely difficult to change.
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