ManuFromParis

When I got this 964 C2, it had a leaking steering rack, but on top of that, the steering was quite heavy :

The main symptom is : when you drive,
1- the steering wheel is heavy to turn
2- the steering wheel and the wheels mostly remain where you let it, instead of returning to 12:00, as on any car.

Here are some more tests and observations :
- On roundabouts or on a very large empty parking lot, if you go slowly you can turn a perfect circle without touching the steering wheel. If you go faster, eventually the steering wheel will want to come back to 12:00, but will never achieve it : you will follow a very very large turn.

- When you’re stopped with engine running or not, if you small turn the steering wheel from right to left and left to right, it is not heavier than on any 964 (I have a 964 C4 and it’s even heavier)

- When you’re stopped with engine running, if you turn the steering wheel from right to left and left to right, and then stop the engine while doing that, the steering becomes instantly very heavy. And it lightens when you start the engine again.

- On the freeway, it’s quite uncomfortable because it’s very difficult to make a very small direction change to stay straight in your lane.

- From a sitting position, if you constantly turn from left to right then right to left with small movements, then start very slowly in first gear, you can feel the steering becoming heavier as speed raises, so it obviously comes with the speed.

- The front lower triangles and bushings look good

- the whole front of the car look totally original, with perfect alignments and all original front trunk parts from all points of vue, and the look of a 120000 miles car, as every car I know (and I know a lot !).

Of course, my first step was to replace the steering rack, rack bushings, tie rods and steering ball joints, but the symptoms remained.

More observations :
- When the tie rods where disconnected, both wheels were totally free to turn one way or the other, with no efforts at all

- When the steering column was disconnected, the steering wheel turned one way or the other, with no efforts at all

2nd step was to replace the steering pump, but the symptoms remained.
The procedure with the full left to full right turns, 10 times, to get rid of any air in the system was performed, with no surprises.

3rd step was to replace, lower main ball joint, shocks, supporting mounts, then reset the front geometry, including several tests of raising or lowering the caster, but the symptoms remained.

Even though the 2nd steering rack was a 2nd hand item with no certification of condition, the symptoms and observations above did not change at all. So we can bet it is VERY unlikely that both racks had exactly the same problem.

I have no ideas where to look or which other tests to perform, except to take the steering rack of a working car and swap it on this car. But that is a triple punishment because I might have to fit parts back to where they belong (those who replaced steering racks know what I'm talking about)

Any ideas ?

Rocket Rob

Have you checked for a kinked or crimped pressure line or restriction? If you take off the return line at the pump and run the engine, if the pump flow up to the rack and return flow well?

ManuFromParis

Lines look fine the whole way, even within the tunnel.
I'm not sure to understand what test to perform with the return flow, but obviously some oil returns to the glass tank

-nick

- With the engine off, the steering should be very heavy. There will be no power assist. This is true for any power steering car.
- Caster will make the steering feel heavier as speed increases. This improves high speed stability.
- When the steering is at full lock, it's not unusual for the wheel to not return to 12 o'clock while driving. Many/most cars behave this way.

What is unusual is for the steering to not return to 12 o'clock at smaller steering angles. I can only think of the possibilities of: too little caster angle or too much toe-in. If the tie-rods are very worn, toe-in could increase with speed. As Rob suggests, a kinked return line would make the steering feel different at idle vs higher rpm, regardless of speed.

If the steering rack isn't leaking, and it turns smoothly without sticking or binding, then you should be able to rule it out as an issue.

What are your current alignment/geometry settings?

ManuFromParis

- Tie-rods are new
- Caster is currently at maximum setting
- Toe-in is 0
- Camber is 0
- steering is equally heavy at any RPM

-nick

Inner tie rods are new too? That's where the flexible rubber bushing sits between the rack and tires.
Camber=0 is odd. Stock is conservative at -0.5°. Even at -1° you're not giving up any braking or tire wear.
Max caster= ? If 993 upper mounts were swapped in at some point, that would give you an extra degree. Though that wouldn't explain your issue.

ManuFromParis

yes, the whole tie-rods are new.
Actually, when I wrote "0" I meant : Stock setting and you're right it's a small -1°
Max caster meant : I've tried several settings with the Caster and the symptom seemed to raise as caster was lowered, so I set it ax maximum possible.
Upper mounts are Dansk for 964 but that's actually the last parts I replaced, with no results.

cjoenck

When you replaced the pump and rack, what fluid did you use to refill the system? Did you go to original spec or something different? There is a simple procedure to flush the whole system.

ManuFromParis

I did use Dextron type, as usual.

But after I did some more tests, including a disconnection of tie rods leading to notice a still heavy steering wheel, with or without engine running.
So obviously the problem was likely located within the steering rack.
I got the rack brackets a bit loose to check if it helped, hoping it could be a problem within the steering column joints.
But it did not helped.

So I started to question this 2nd rack.
I fetched the 1st rack and a 3rd spare rack that I had on shelf, just to compare.
The 1st rack was almost impossible to move by hand while the 3rd was moving freely by hand from the steering axle.
So even while the 2nd rack was still in the car, the heavy steering wheel with disconnected tie rods implies this 2nd rack had the same problem as the 1st, less the leaks : it was just heavy.

So I spent the afternoon swaping the 2nd for the 3rd rack and everything is now fine.

I did not want to consider a failed rack again, because it seemed so unlikely, but I guess that seller lied to me when he said it was removed from a working car.

I was quite inspired when I bought that 3rd rack and I will now send these 2 failed racks to be refurbished. I know it will be usefull some day.

So when you purchase a second hand rack, ask for a video where the rack is moved by hand from the steering axle !

Marian76

Have you considered the steering rack bushings?

https://rennlist.com/forums/968-foru...fter-turn.html

I understood that this kind of behaviour is somehow normal.