Q45 Power Steering Intermittent Problem

[komradklaus]

I recently got a 1996 Q45t with ~320k miles, and, being a very old car with tons of miles, it has some problems, several of which I've taken care of already. The power steering currently will intermittently act up. Sometimes it feels like I have no power steering at all, others it feels like the power steering starts and stops as I turn the wheel. The problem rarely (ever?) presents itself on startup and seems to only start in earnest when the car is warmed up, but not every time the car is warmed up.

At first I thought that I should look at replacing the power steering pump, but when researching the problem, I found these:
tip-for-powersteering-problems-t413728.html
steering-shaft-to-rack-u-joint-question-t29640.html

These posts suggest the problem could lie with the u joint instead. Anyone have any ideas on how I can more accurately diagnose the problem before I go tearing the car open or spending money on parts?

The car has recently had a tie rod end, two steering rack bushings, a control arm, and a tension rod replaced up front, so I know that none of those parts are the source of the problem.

[Q451990]

to NICO! Great first post!

In my case, the problem was worse when the car was first started, and then loosened up as the car was driven for a while. The easiest test is to just remove the u-joint and see how frozen or "notchy" it feels. Do you notice any weirdness with the speedometer when you have this issue? I believe the speed sensor passes through the instrument cluster and to the P/S control unit. I think there's also a solenoid that receives an on-off signal on the rack that can mess up? I've been very lucky to only have the u-joint issue on mine.

[komradklaus]

I have driven the car for several days and tried to watch for any correlation between any of the gauges and any problem with the way steering feels. There is no oddity with the speedometer. My tachometer is broken and, depending on mood, displays 0-infinite revs, bounces randomly, or displays the actual correct rpms. I have observed the steering problem under all of these varying tachometer displays. I think that the u-joint is the most probably explanation, so I'll be taking a stab at that as soon as I have time.

[Drake57]

IDK about 96, but the 91/92 models have a bypass on the power steering pressure line. A higher voltage applied to bypass increases assist. PS controller module takes into account vehicle speed, decreases assist as vehicle speed increases. To test, apply +12 volts to bypass, you should have full assist, remove +12 from bypass, you should have nearly no assist. The bypass is on the PS rack.

[Drake57]

On my 92, it was the PS controller - at times I would have full assist even at speed, other times no assist regardless of speed. Replacing the controller module cured it.