chrisp3

A month ago heard a stronger than usual hum noise from the power steering. Purchased MB power steering gear lubricant (Q 1 46 001) and added about 100 ml to bring the power steering reservoir level to the 20 degree C level. Hum seemed to go away.

I then purchased a new power steering reservoir filter and used an oil extractor vacuum to pull a few more ml of fluid from the return line and while replacing it with new power steering oil. Then the humming got louder. It starts when the car is just started in the morning and it does not seem to change when it gets hot.

Last weekend I then removed the drain plug from the power steering gearbox and let the power steering oil flow out. I had purchased another quart of power steering oil and used about 600 ml ounces to fill it up. I started the car and the fluid swirled around the reservoir and foamed up. There are air bubbles on the top of the reservoir for about a minute after turning off the engine. A day late the reservoir is at the same level at the 20 degree C full mark. I read that the capacity of the power steering system is 1.4 liters so I’m not certain if draining from the gear box completely purged the system.

I also have an occasional squeak when the front end of the car dives, as in braking or going over a bump. It does not occur when I push down on the suspension. I’ve been told that it could be the ball joints.

Questions: Could the squeak, from a ball joint or something else, indicate binding in the steering system? Could this be overloading the pump and causing this hum?

Thanks.

sosh

Do not believe that the squeak from the ball joints have any effect on the power steering. Hum is most likely from either an airleak or a worn power steeing pump. Given the age of the vehicle its most likely the pump but try bleeding the system by turning the wheel full left then full right a couple of times with the engine running. Then, shut down and check the level top off as necessary.

chrisp3

Sosh was right! I had added a few ml of power steering oil to the reservoir and had driven to show the problem to a mechanic friend. I started the car, opened the hood, opened the reservoir, and the hum and foaming of the oil had disappeared. He said that when chainging fluid to lift the front wheels off the ground and then move the steering wheel back and forth several times to purge air from the system. I then did just that and any reminant of a hum or foaming went away.

I think my troubles started when I had sucked out fluid from the reservior while the engine was running. I believe I introduced air when the reservoir level dropped. The rate of circulation through that reservoir is quick. Just like motor oil, I would recommend draining the fluid from the gear box, replacing the drain plug, then refilling the reservoir with the engine off.

Thanks for the advice.