docmirror

Splitter valve = "spool valve" in the 928. The pump provides the pressure to this valve, and the valve directs the fluid left of right, depending on the need. Anyway, this is what's going bad. It could be the torque sense rod that Jim mentioned, but this is a low failure item on most cars. The valve, however is a fairly common repair, it should be part of the rack rebuild.

If your car tends to 'pull' gently to the left or right, this is a common cause. That valve needs to stay very centered and provide equal pressure to either side of the rack(ram) when not turning. When it wears, there is slighty more pressure on one side than the other, neccesitating a constant correction by holding the wheel to oppose the slight pressure.

Mark87AT

Well it is seeming more and more to point to a steering rack rebuild (the steering wheel is fine, no play) the problem is somewhat inconsistent. I noticed yesterday for a few minutes the steering to the left was almost normal, then back to muscle building at a stop or low speed. My biggest problem right now is no garage, so any work is going to have to wait until the rain stops...

Mark87AT

So, is replacing the steering rack difficult and perhaps the more pertainant question is: Can I do it with the car on 4 Jack stands? or is this a job that requires a lift? Mark

Nicole

Bill and I have done it twice on my car. Not a fun job without a lift! It is doable, though.

Initially I got a rebult ZF rack, but the teeth for the steering column connector were off by a half tooth, and my steering wheel was no longer straight. I hear that's common with those racks. Also, I have a 91 that is supposed to have the higher power assist - but with the ZF rack the steering was like a freight train.

It was subsequently exchanged for the proper Porsche rack, and now things are purrfect.

If you consider adding larger/wider tires in the future, consider upgrading to the '91 and later steering rack. Then, when the pump goes out, upgrade to the newer, lighter, and higher pressure pump also. It makes a world of a difference!

the flyin' scotsman

Mark.........if you don't have a lift raise the car onto stands and remove wheels. You may want to consider removing the brake calipers, rotors and sway bar, all for the sake of under car room. After which removing the steering rack is relatively easy; 8 nuts, 4 of which are a pain to counter hold and 1 bolt. After these are removed you can get the plate off and hence the rack. Mark the position of the steering shaft to rack and remove; undo the power hoses and remove. The new decision you will have is whether to replace the tie rod ends or not. Yes then remove the tie rod ends and the rack assembly is in your lap; no then you should unscrew the tie rod ends from the rack while its stil in situ.

Replacing is the reverse with the complication of ensuring the new rack and steering wheel are centred before attaching the steering shaft universal joint.

Mark87AT

Well, I was finally able to get the car up on jack stands. There is no significant difference turning the steering wheel to the left and to the right with the engine off or on, with the front wheels off the ground.... I guess this suggests that the spool valve (or splitter) is potentially bad and as such the rack needs replacing? Mark

Mark87AT

El bumpo!
So before I go ahead and replace the steering rack I thought I would recap my sharks symptoms and things I have done and see if people concur the rack is the most likely culprit.

Power steering is essentially dead to the left (about 85% of the time)
at a stop with some force on the steering wheel to the left, reving the engine has no effect.
No apparent PS fluid leaks from the boots(I have not removed them)
Steering wheel has no play back and forth or in and out
With the front of the car up on jack stands there is no difference turning the steering wheel to the right or left either with the engine off, or on.

Thanks! Mark

Garth S

Mark.
Rack replacement/rebuild still comes up as the decision.
Rack removal is reasonably easy. It can be done off 2 jack stands, but 4 are better.
First check for tie-rod wear before disassembly ( horizontal plane wheel play). If they are good, then they can be loosened at the rack end - and if reinstalled in the same rack rebuilt, the toe adjustment should not change. Just one note on the removal - carefully counterhold the protruding rack ends when removing the inner tie rod joint. Disconnect the battery, play with the hoses, get covered in red ATF, .... all the usual!

docmirror

If you have no leaks, and the steering is tight and not sloppy, you can probably get away without a whole rebuild of the rack. I know, the rest of the forum will grump at me, but based solely on the SYMPTOMS, you can try to fix what's broke rather than a generic rebuild. If you want to go crazy, take the rack off, and take it apart to locate the spool valve. Inspect it for damage or wear in the bore, and see if you can replace or repair just that.

It may not be a customer servicable part, and only done on a rebuild, but try to follow the symptoms, and not shoot it with a shotgun approach.

Mark87AT

doc,
Hmmm.. interesting thought, but I think I might just go with a complete remanufactured rack, I would hate to do the spool valve and then have the other seals go in 6 months or a year from now and have to replace the whole thing anyway.
Garth,
Well the delightful upside is I am pretty sure a friend of mine has access to a shop with a lift we can use to do the job!!! yay! Devek replaced the tierods 2000 miles ago so I shouldn't have to replace them, should I? Mark

Bill Ball

Mark: Let me know when you want to replace the rack and I'd be glad to wrench on it with you, ESPECIALLY if you do it on a lift.

Mark87AT

Hey Bill,
Cool. Yeah, I just found out a new friend is a mechanic at a european auto shop over in San Rafael (I think). We can use the lift during off hours. I am going to order the parts and then we'll schedule a date, will definitely keep you posted!