Weird steering problem.
 

I own a -85 euro 500 sec with a peculiar problem. When the engine is off, the steering is nice and tight with no slack - i.e. 1mm of movement on the steering wheel is noticeable on the front wheels. As soon as the car is started, however, there is a slack of about 1.5-2 inches of steering wheel movement without the front wheels turning. As you can imagine, this is very uncomfortable while driving highway speeds...the car will suddenly veer one way or the other and I constantly have to correct the line of travel with the steering wheel.

What could be causing this - a worn power steering pump?

Appreciate any help...

Blade_HST

I think the excess movement is in your steering system, but with the engine off you are not moving the steering wheel enough to have it show up.

Try lifting the front of your car so the wheels are off the ground and then try it with the engine off. Have someone move the steering wheel while you inspect every link and connection.

Often quick rocking back and forth of the steering wheel will make the steering system report any loose pieces.

Check the idler arm bushings, tie rod ends and also your steering dampener. The dampener can easily be checked by removing one end and pushing and pulling on it.

If you are wondering about your pump, try changing the fluid and also replacing its filter.

Keep us posted,

Haasman