FiveElements

I rebuilt my 89 rack 2 years back. The seals at the ends were leaking but I had a fully working rack. As I rebuild the hydraulic area and replaced the 4 (think it was bout 4) seals in the main yoke area, they seemed a bit smaller that what I took out. I'm not sure if that was the problem, but a couple months later, no power steering function. The rack did not leak though. The rack still does not leak. I called 928 Motorsports and discussed this with them and they considered dirt in the lines or something not flowing well? I then flushed the entire system, but no change.

A few months later, I then replaced the steering reservoir (because of the filter in it) and again flushed the system with fresh ATF. (yes, not steering fluid)

Here's the weird part... the power steering works perfectly at start up on a cold day. As the car warms, the power assist stops working partly on left turns and fully on right turns.

Any recommendations? (before I just buy a new or rebuild rack and tie rods for a bazillion dollars) Maybe the main seals are not the right size or the cylinder walls are worn beyond the new seals ability to work? 928 Motorsports is recommending I use an oil thickener or steering rack stop leak to swell the seals.

Carl Fausett

I recommended he try a bottle of Lucas Steering Rack Stop-Leak as a diagnostic tool. It is not a fix nor a cure.

Because he mentioned that the power steering works flawlessly when the car is cold, and his power steering goes away as it warms up - I think that how it responds to the more viscous Lucas product might help to locate/isolate the root cause of the problem.

westija

Sounds like some leak (internal?) as the fluid's viscosity changes with an increase in temperature(

928 at last

Essentially the same problem I had / have. It gets worse to the point where there's virtually no assist at all. No leaks, rebuilt pump (that fixed it for 15 minutes), flushed, no noises.....just no assist.
I suspect crap is in the spool valve somewhere. New rack on the near term to-do list.

Lizard928

The fact that it builds pressure when cold tells us that the pump is working.

How long does it take before it stops working?

I believe that you likely have a problem in the spool section of the rack.
A rack stop leak, will NOT help, and is imo a terrible idea.

Here is what is likely happening.
When you removed the spool valve (part the steering knuckle attaches to), it has 4 o-ring backed seals.
Where they ride in the housing can wear and leave ridges, and sharp edges.
It is likely that one of these ridges has put a 'nick' in one or more of the seals.
You will need to pull the spool out, use some emery cloth or fine scotch pad to remove any burrs in the housing and to ensure everything is smooth.
These 4 seals (and backing o-rings), will need to be replaced.
Coat these seals in a fair bit of grease when installing. Do NOT force this spool in.
You need to grab it with vice grips and rotate/wiggle it to get it to go in, it should slide down and in with NO real effort. If it requires effort it is binding on something (likely the lower bearing/race), and just needs a little more wiggling.

FiveElements

Thanks Colin

It also seems to me like the 4 o-rings in the spool are the problem.... poor seal or damaged. I mentioned that to the 928 Motosports guys. I'm thinking I better try replacing them again. Any suggestions where to find those seals by themselves?

What type of grease should I use to re-seat the spool assembly? Any other suggestions?

Carl Fausett

Keep in mind that the bore of the rack also wears at each location where a seal rubs on it. Granted, the seals wear out first - but that doesn't mean that the aluminum does not wear also.

Eventually, if there is enough wear in the bore (especially if dirt has gotten in and caused a scratch in the metal) there is no seal that will fix that.

Lizard928

You will need a complete reseal kit to fix this problem.

FiveElements

So the bottom line is... rebuilding a rack with only seal is a bad choice. The spool wears anyway and makes it useless to just replace seals only, even though the end seals may stop leaking into the boot area, the spool in time will not maintain pressure just due to wear. (which only took a few months for me)

So either buy a rebuilt rack from 928 International or have 928 Motorsports include new aluminum spool parts for the main hydraulic assembly. It would have been nice if 928 Motorsports would have explained that so I didn't waste $70 and 20 hours of work pulling the rack out twice. That rebuild kit probably should include new spool components or be removed from the market.

Lizard928

99% of the racks do not have enough wear to cause a problem in the spool housing.

I doubt that yours has enough wear either.
I believe you will simply need to replace those seals and remove ridges which likely cut the seal on install.

FiveElements

Ok Colin

I'll give that a try. Good to know

Carl Fausett

I agree.

That's why I mention dirt incursion. The steering rack system is exceptionally sensitive to dirt.
A single scratch or a small piece of debris will do you in. Most rebuilt racks I have seen come with a big red tag that insist you also replace the hoses and the reservoir at the same time, or your rack warranty is void.

Replace the seals again, de-burr the edges like Colin suggested, flush it out before assembly, assemble carefully, and you should be good.

White Lightnin'

When you get around to pulling the rack for a reseal/rebuild... install the delrin bushings. It makes a HUGE difference!

FiveElements

I replaced the rack bushings with stock rubber ones. Are you talking about the hard ones? Or are you talking about the solid tie rod ends?

928Myles

The delrin bushes are semi hard (plastic) ones that replace the stock rubber / steel ones.

I agree, if your current bushings are in poor condition, that it will make a huge difference. When I replaced mine the difference was noticeable but not huge.

Incidentally, I am in process of currently rebuilding my rack (no options for a rebuilt RHD rack from any of our vendors) so taking a great deal of interest in this thread.

Hope you get it sorted.
Myles