Hello all,
I'm pretty new to this side of the board. Most of the time I spend on the 240 side. But my wife's 93 945 has developed a strange problem and for the first time, researching the 700/900 FAQ didn't resolve my problem. At low speed, when turning, the steering shutters, or maybe chatters is a better word. It's a vibration that can be felt in the steering wheel, and throughout the car. I can also see it in the front wheels. I have changed the P/S fluid, tightened the P/S pump belt and checked the front end for looseness. No faults found and it still does it. When I go down a slight hill and turn back and forth the problem is there. But if I shift into neutral and rev the engine a little, (and thus spin the pump faster) the problem goes away. I feel like it's a pump, but I'm told these things hardly ever go bad. And if it is, can I just adjust the thing? The car's only got 107,000 miles on it. Thanks for the help!
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It's Jim (in Hartford CT)

Dear Iapetus,

May this find you well. Has the car even been in a front-end collision? Even if it is has not, the power steering pump bracket could be bent. That means that the axis of the power steering pump pulley no longer is parallel with that of the crank (main) pulley. The belt could bind on the power steering pump pulley, and slow the pump. When you rev the engine, that overcomes the drag, so the steering works properly.

Take a straight edge (a metal ruler, 18" long) and put it across the face of the crank pulley. Then, using a smaller ruler, measure from the trailing (back) edge of the 18" ruler, to the face of the power steering pulley, on opposite edges. If the two measurements differ (by, say, more than 1/8"), then the power steering pump bracket is bent. It should be replaced.

It is also possible that the main pulley (crank pulley also known as the harmonic balancer) has failed. It consists of a steel core, a rubber insert, and a grooved steel outer ring (on which the belts bear). Over time, the rubber insert deteriorates. When that happens, the outer rings slides around the steel core. This means less power is transferred from the crankshaft, to the peripherals (power steering, alternator, and air conditioning compressor).

When the car turns, that puts maximum stress on the power steering motor. If the crank pulley has failed, too little power reaches the power steering pump, and the pump gets "cranky".

I recently changed the crank pulley on a 93 945 with 106K on it. To find out if the crank pulley has failed, take some white out, and draw a line from the inner surface straight out to the face of the pulley. Go for a drive. If, when you return, the white line is straight, then the pulley is fine. If, however, the white line has separated into two segments, then the crank pulley has failed. That is, the white line on the outer section no longer aligns with the while line on the inner section. Regardless of the state of the power steering motor, you'll need to replace the crank pulley. That may cure your problem.

Hope some of this helps.

Yours faithfully,

spook

My 89 240 had a "shudder" in the steering when still or very slow - almost as if the tires were jumping while turning, instead of swiveling smoothly to turn.

Turns out I had 2 problems:
1) loose small universal joint in steering column (there are 2; they allow the steering gear to follow the bumps while leaving the steering wheel fixed in its mount). and
2) bad steering rack - loose, sloppy, and leaking fluid out the seals at the ends. Replacing was about a $500 job, but really cleaned up the steering roughness. At that cost, I only did it when the thing got so bad that it became hazardous to drive.

It ain't just low P/S fluid - sorry!

Thanks for the response.

Just for the record, the rack is absolutely tight. No leaks and no play whatsoever. The steering column U joints also have no play with nothing to make me believe they have seized up either.
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It's Jim (in Hartford CT)