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Premium Member
2015 C300W4; 2007 E350 W211; 1992 300SE W140
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134 Posts
Discussion Starter #1
I have replaced several parts on my 1992 300SE W140. The vehicle has 240K on it and most of these parts needed replacement anyway

1. Water Pump (new)
2. Power Steering Pump (used)
3. Belt Tensioner (new)
4. Belt Shock (new)
5. V Belt (new)

The belt was slipping and there was a lot of noise coming from the P/S and water pump. I couldn't tell which one. The noise has gone away and the car runs and functions perfectly. The only problem is now I have foam in my power steering fluid. I sucked air into the system when I was purging the old fluid. I have not been able to get rid of the air. This was not happening before I replaced the pump (which may not have needed replacement after all). I had a tire guy turn the wheel 30 times lock to lock while the wheels were up. I drove the vehicle 50 miles afterward. Still the same problem. It only foams when I turn the wheel when the car is stopped or at very low speeds. Like parking.

So what do I look at now? Is it possible that the pump is making the foam? I have checked and tightened the lines. There are no obvious leaks. Is it possible that the gearbox has a leak and letting in air? It was not doing this before the pump replacement. The pump was used, but I have been assured by the guy I bought it from that it is a good pump.

Somebody please help me! I am out of ideas. How tough is the gearbox replacement?
 

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Registered
'84 300DT, '97 S320
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682 Posts
I recently replaced the seal (and other little gaskets in the kit) in my P/S pump (~209k mi @ the time), 'cause it was leaking out the shaft. Like you, jacked up both wheels (w/ 2 MB spare tire jacks - man that's a lot of weight on those). I put some pix here.

Also, turned about 30 back and forth with the engine OFF (actually my gracious wife did), while I added fluid to keep air from getting in. Assuming you did yours engine-off also, since the wheels were jacked up?

Anyway, no problems at all.

May be your pump. Search here and elsewhere, to see how to take it apart and look for worn pieces. Lot of fluid will still be in pump after sucking the fluid out, so be prepared to catch fluid everywhere. Fortunately I had plenty of towels (real, not paper) on the kitchen table when I opened it up. Mine showed hardly any wear. Six-cyl's pumps are the easiest to remove.
 

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Registered
nothing broken. finally!
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2,619 Posts
Your pump is aerating. Ít's used after all, how do you know its not worn out?
 

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Premium Member
2015 C300W4; 2007 E350 W211; 1992 300SE W140
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134 Posts
Discussion Starter #4
I really don't know if it's worn out or not. I guess that if I put the old one back on and it stops foaming, it's the pump thats worn out right? Is there an easier way to tell?
 

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Premium Member
2015 C300W4; 2007 E350 W211; 1992 300SE W140
Joined
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134 Posts
Discussion Starter #6
Would doing a re-seal fix that problem? Or, do I need a new pump?
 

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Registered
'84 300DT, '97 S320
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682 Posts
Just curious: who were you responding to when you said "Thanks, I'll look into it?" You have 3 posts in a row, and it looks like someone else's posts have been removed.

Since you were not initially sure if the pump was bad, I'd put it back on. I don't think a bad shaft seal (or the other ones) would cause the bubbles. It wold just leak. My W123's pump has 370k mi, and it's never leaked, so maybe your original one is a pretty good one too, and hopefully it was just the water pump making noise.
 

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Premium Member
2015 C300W4; 2007 E350 W211; 1992 300SE W140
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134 Posts
Discussion Starter #8
Thanks all for your input. As it turns out, the pump that I installed was missing a bolt on the front, causing it to suck in air. I never checked that before. I just assumed that the pump that the guy shipped me was complete. Problem solved, and in the process, I learned a lot. That's what I love about this site. I get to learn while I save money. There cars are complicated, but well engineered. It is worth all the time I spend working on my car when I finally complete a project like this..... I also get to drive a car I could not otherwise afford. I love my w140!

I am glad I did not have to go back to the old pump. I was a little tired of swapping parts. Now I can just enjoy my MB for a while longer... Thanks and Cheers to all!
 

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Registered
'84 300DT, '97 S320
Joined
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682 Posts
Congrats! It's real nice finally finding a simple fix, eh?

I'm with you about the learning. Some of my friends ask how I ever learned so much about fixing car stuff, and I say "it all started with replacing an air filter, then changing oil, then spark plugs, etc. Next thing I know, I'm changing friends' water pumps". I owe it to my dad who showed me how to change drum brakes, and how to use a timing light. Strange, though, I don't own a light, nor ever used one, but man I've changed a lot of brakes.
 

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Premium Member
2015 C300W4; 2007 E350 W211; 1992 300SE W140
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134 Posts
Discussion Starter #10
It is really great to be a part of this online community. I would be lost without BenzWorld. Almost everyone here is very helpful and generous with not only their knowledge, but in other ways as well.
 
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