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Discussion Starter #1
I have an 87 300td that is leaking hydraulic fluid. It's been difficult to find any documentation on how the power steering and the self leveling systems work, so I thought I'd ask on the forum and see if somone knows these systems.

The leak started out slowly but has been getting worse in the last month or so. The info that I have states that my car uses a tandem pump for the power steering and self leveling systems. It also says that they use two different types of oil.

From what I can tell, the leak is coming from the screw on cap that holds down the power steering reservoir lid. The cap is vented and when the engine is running, I can see fluid coming out of the vent holes. This doesn't make sense to me since I am having to refill the self leveling reservoir not the power steering reservoir. They are supposed to be two seperate systems that use two different types of oil right?

When I remove the PS reservoir lid, the fluid level is right at the top with a little spilling out and it's a darker color than the ZH-M fluid that I use in the self leveling reservoir.

I'm assuming that the vent on the cap is there to release excess pressure so any ideas on what could be causing that? Dirty filter? Blockage in the system?

Actually, the more I think about it, the more I think it's a dirty filter. That would create excess pressure and the fluid would come out the vent instead of going through the system (As designed?).

Still doesn't answer the question of two types of fluid though. Anyone know how these danged systems work?
 

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2002 CL55 AMG, 1993 190E 2.3L, 2004 SLK320 Sport
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1,733 Posts
I had the same problem, until I had the filter changed and the fluid changed to automatic trans. fluid! This worked for me!
 

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Discussion Starter #3
Regular power steering fluid will work? I've been told by numerous sources to only use the Mercedes stuff. Any one else out there have a good experience using regular ATF?

So, I changed the filter and topped it up with fluid and it's still leaking. Anyone have any ideas about what causes the power steering vent cap to vent oil while the engine is running?

Thanks,

Nick
 

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E220 1994
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72 Posts
DId you bleed out air before starting the engine. According to the Haynes manual, you need to stop the engine and turn the steering wheel to both extreme to unlock air. Then with an assitant keeping an eye on the fluid level and another one starting the engine. THe fluid level should drop and top up may be necessary. THen stop the engine and redo to unlcok air out of the steering gears.

Hope this may help.
 

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Discussion Starter #5
Okay, I tried bleeding the steering system as drtung advised (Thanks for the tip) but no change.

I noticed something interesting after I bled the system and was testing the steering. When the wheel is turned with the car running, the leaking stops. The leak only occurs while the car is running and the steering wheel is not being turned.

This is leading me to believe that I may have a bad seal in the pump which is allowing backpressure to push back into the reservoir. Also, I double checked with the dealer and they confirmed that the power steering and self leveling systems are two seperate systems that share the same pump housing but use different oil. Since I'm having to refill the self leveling reservoir and I'm seeing the leak from the top of the steering reservoir, I'm thinking that there is a constant small leak between the two systems. When the steering pump is not pumping (IE, when the the wheel is not being turned), the self leveling fluid is pushing into the steering reservoir and filling it to the point that it comes out the vent.

Do I hear an amen?

The dealer has a pump rebuild kit so it looks like I may be rebuilding and flushing the system if someone doesn't have a better idea.

Thanks,

Nick
 

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E220 1994
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Sorry to hear that but I heard that it is quite difficult to redo the steering box seal. If you find any walk-through , please let us know.
 

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'07 GL320CDI
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Well, you know there is supposed to be a gasket on the underside of the pwr steering pump cover.

The black knob on the top is NOT a vent.
 

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E220 1994
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TOday I also find that my steering box is soaked with oil. Is the 94 W124 steering box known to be leak easily? I just cannot find any web site to redo the steering box seal from the internet after 4 days 10 hours search. Nor is the Haynes or any Mercedes repair manual mention about this.

Anyone can help and I will be much appreciated.

Or should I just do the same things as other guys do- just top up the same rate as the leak does?
 

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2004 SL55 AMG
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505 Posts
[8D]
My steering box drips from the opening around the Pitman arm. The dealer I bought the car from is having it fixed at his expense right now. I expect to retrieve the car on Monday. As far as I know, they are replacing the O-rings and other seals. I'll report back after seeing what they actually did.

Cheers!
Dave
 

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2004 SL55 AMG
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[8D]
Hi Snick,

I got my car back from the dealer yesterday. The leak from the steering box at the Pitman arm is gone. They rebuilt the box with new seals and O-rings. They also replaced the coolant expansion tank. Apparently, that was leaking too. Since these were no-charge repairs, (the car was supposed to be mechanically sound when I bought it from them in March) I don't know what the fixes are worth.

BTW, the loaner car was a new Jag X-Type 3 Liter sedan. What a harsh, noisy bugger that thing is compared to the Benz. I have to admit it does handle well.

Cheers!
Dave
 
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