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  #1  
Old 06-11-2010, 06:12 AM
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Modifying Power Steering Pump Valve

To get more boost as the steering is quite heavy around town either by shimming or increasing the valve orifice size. I'm thinking of giving it a try.
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  #2  
Old 06-11-2010, 06:24 AM
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What car / pump are you talking about?

For example if you have a 65 bar pump on a W123 people commonly interchange with the higher pressure pump from a W126...
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  #3  
Old 06-12-2010, 06:40 AM
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1988 300E M103 W124. Is there a W126 pump I can swap into it or just change the valve?
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Old 06-12-2010, 09:35 AM
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Not sure

Quote:
Originally Posted by tilac1 View Post
1988 300E M103 W124. Is there a W126 pump I can swap into it or just change the valve?
Sorry I don't know the answer to that one - but the W126 pump is rated at 82 bar (I think). People have reported here that swapping from one pump to the other makes little difference.

I'm not sure you're going to get the desired effect by changing the pressure of the pump - may be may be not - I assume you've done the obvious and checked to make sure all of the steering joints are working as they should?
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  #5  
Old 06-12-2010, 11:43 AM
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Yes, all is in very good condition, 60K miles on the car. Just need more assist for the power steering around town. I may pull out the pressure valve and try to modify it.
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  #6  
Old 06-13-2010, 10:38 AM
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Good luck - I just had a thought though - tire pressures OK? However, if it really is a problem with the 'design' then I'd get a good second hand unit before starting any modifications on the existing one. Just in case...
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  #7  
Old 06-13-2010, 10:56 AM
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Ya, good idea. I'll play with an old one first.
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Old 06-21-2010, 07:53 AM
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I think the pressure increase will not change the feel of the steering. You need to investigate making changes in the steering box. Specifically the mechanism that opens the hydraulic valves in the steering box. There are some springs that if they are made to be weaker will allow the valve to operate with less effort from the steering wheel.

My 300E steering is so powerful that you can steer it in a parking lot with nothing more than your little finger.
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  #9  
Old 06-21-2010, 05:32 PM
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I like my steering stiff. Keeps things manageable at speed.
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Old 06-21-2010, 07:39 PM
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Umm, variable assist.
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  #11  
Old 06-21-2010, 07:46 PM
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Quote:
Originally Posted by babymog View Post
Umm, variable assist.
Exactly. Mine isn't very powerful at low speeds. Definitely not 'turn with a finger in the parking lot.' No complaints on highway but it seldom sees it.
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Old 06-21-2010, 09:06 PM
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Whatever is different between your early years car, and the later years cars, makes my '94 and '95 E320s steer very easily at parking-lot speeds.

I'd like to know which part is different also, as I'd make the change to my '87.
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Old 06-22-2010, 06:18 AM
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Quote:
Originally Posted by babymog View Post
Whatever is different between your early years car, and the later years cars, makes my '94 and '95 E320s steer very easily at parking-lot speeds.

I'd like to know which part is different also, as I'd make the change to my '87.
So your '87 is significantly less power assisted? I checked later pumps (94-95)on ebay and they are 110 bar, same as my '88 pump. Something must be different but I can find no mention of it.
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  #14  
Old 06-22-2010, 09:25 AM
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I respect Larry's opinion, but I must say that my 300e is nice when in the parking lot. Of course it gets really easy on the high way and you have to be careful. I don't have a strength issue but I would not mind a little more power steering in my bigger cars while going slow. I guess that is why they invented variable ratio and all the other improvements.
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  #15  
Old 06-22-2010, 10:16 AM
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No disrespect to Larry's opinion either, but it's not about strength anymore than power brakes are about strength. Provided the system has a good balance between assist at low speeds and feel at higher speeds, I prefer the greater assist of my '95. It has great feel, but doesn't fight me like a 123 around low-speed corners. The parking-lot manuevers aren't really the issue, it's just so un-refined feeling going around slow corners to have it pulling a few pounds of force to hold the wheel into a low-speed turn where my '94/'95 cars are a two-finger job at low speeds.

I'm pretty sure that Mercedes spent the money to re-design and re-tool the later 124 for a reason, and since the components aren't any less expensive in this case, it couldn't have been motivated by cost.

So for those of us who prefer the lighter feel at low speeds, not interested in whether we need more arm strength or whether the high-speed feel is inadequate, I can tell you that I'm quite happy with the feel of the late-model 124s at 110mph-135mph, the feel on circuit tracks and on the highway. The early 124 is simply too heavy feeling and tries too hard to re-center.

Now back to the original poster's subject.

I question whether the difference between the early and later cars is more geometry than boost? Could easily be the steering box has lower pressure actuating valves, but could it also be a reduction in caster? I know that the control arms are different part numbers, what else has changed?
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