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'08 ML320 CDI
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Discussion Starter #1 (Edited)
This is kind of an urgent question. I am on my third (!!) power steering pump. All were replaced with OEM units. Now this one is leaking too?! My mechanic told me we could maybe try an aftermarket unit (I believe Luk is the brand).

Anyone familiar with this or have any feedback?
 

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Discussion Starter #3
Where does it leak?
He told me it's leaking out of the shaft...

I also had to replace the seals in the power steering rack and reservoir at some point but that was a cheap fix.

Each time I spent some time in freezing temps for a few days and come back home, the power steering gets leaks. This stuff doesn't seem very weather resistant.
 

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99 ML430, 00 ML320, 05 E500 4matic Wagon
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I am not sure what is happening. I live in climate that gets from 90º+ to sub zero and pump #2 which
is an OEM MB pump from a dealer is still going strong.
 

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Discussion Starter #5
I am not sure what is happening. I live in climate that gets from 90º+ to sub zero and pump #2 which
is an OEM MB pump from a dealer is still going strong.
No idea. I don't even drive it that much and the truck gets garaged and resides in Socal; guess it's been pampered too much with this weather and turned into a wuss LOL

Seriously though; how does this keep happening?!?
 

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No idea. I don't even drive it that much and the truck gets garaged and resides in Socal; guess it's been pampered too much with this weather and turned into a wuss LOL

Seriously though; how does this keep happening?!?
You may want to get a second opinion. I am on original P/S pump at 199k. Never had a leak. Replaced faulty return hose with my own solution some years ago. Since then only time I had to add fluid was radiator replacement.
 

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Discussion Starter #7
You may want to get a second opinion. I am on original P/S pump at 199k. Never had a leak. Replaced faulty return hose with my own solution some years ago. Since then only time I had to add fluid was radiator replacement.
Not much doubt the pump is bad. The guy is very competent and it's most definitely leaking.

This has been my power steering story (mileage probably off a bit):
* 70k ish miles: pump leaked; replaced with a new OEM
* One week later: new pump leaks (free replacement; again OEM)
* 80-90k miles; new power steering leak; this time it's the rack. Cheap fix by replacing the seals
* 11xk mi: leaking around the power steering reservoir; cleaned the seals, tightened everything back up and good to go.
* 124k mi (now): third pump is leaking?!

This is almost bizarre. Is there anything else that could put extra stress on the pump making it fail so quickly? It shouldn't even have much strain because 90% is fwy driving in a straight freakin' line!
 

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When major air gets into the system (which can be over time from a small leak reservoir-hoses, etc) then that air really really thrashes the system.

It's air leaks, not the pump, the air thrashes out until the weakest part of the system goes...

You're paying for a "OE" pump at $800 each ? I consider LUK OE quality, but maybe that's just me..
 

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Discussion Starter #11
When major air gets into the system (which can be over time from a small leak reservoir-hoses, etc) then that air really really thrashes the system.

It's air leaks, not the pump, the air thrashes out until the weakest part of the system goes...

You're paying for a "OE" pump at $800 each ? I consider LUK OE quality, but maybe that's just me..
Hmm, maybe air does get in the system. I did drive up to 10,000 feet, which definitely creates a difference in pressure. Still shouldn't matter but could've been a contributing factor? Not sure...

I believe I paid somewhere around $400 for the OE pump. I'm just going to try the LUK for the sake of picking a different manufacturer.

Really hope this is the final replacement?!
 

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My question is what is blocking the pressure side?
 

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What do you mean? All I meant was that the outside air pressure drops at altitude, so anything sealed will expand (think of a bag of chips).
What is blocking the fluid (high) pressure from going thru its designed path?
 

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Discussion Starter #15
What is blocking the fluid (high) pressure from going thru its designed path?
I don't think there's any blockage anywhere. These PS pumps just seem to keep crapping out on me with no real explanation. I hope the next one lasts longer than 40k mi...
 

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I don't think there's any blockage anywhere. These PS pumps just seem to keep crapping out on me with no real explanation. I hope the next one lasts longer than 40k mi...
Other then the pump makes pressure and if it cant get rid of said pressure, it burns up.
 

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It's still at my mechanic; he'll be working on it tomorrow. I'll ask him if he can check for any blockage.
The best way is to take it apart piece by piece and check "inside" the lines, cooler (if equipped), steering assembly, and return hoses. You must make sure there is no-blockage of any kind. I have found "Bars" leak, brass metal spaghetti, and clumps of what looks like bearing grease inside some customers cars.

Sometimes back flushing the lines out with air will dislodge any blockage. Sometimes you have to get chemically involved and yet sometimes, you just have to replace parts.


But three pumps means there is a blockage of some kind.












I DID not say this, but for some REAL problem cars, I have used Honda power steering fluid with excellent 100% results. But only after I fixed the original problem. I had one guy bring back his 55 with the complaint it was too easy to steer. What are you suppose to do about that?
 

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Discussion Starter #19
I really appreciate the information. Hopefully that is the issue and it can be settled once and for all.

Will report back. Thanks again!

The best way is to take it apart piece by piece and check "inside" the lines, cooler (if equipped), steering assembly, and return hoses. You must make sure there is no-blockage of any kind. I have found "Bars" leak, brass metal spaghetti, and clumps of what looks like bearing grease inside some customers cars.

Sometimes back flushing the lines out with air will dislodge any blockage. Sometimes you have to get chemically involved and yet sometimes, you just have to replace parts.


But three pumps means there is a blockage of some kind.












I DID not say this, but for some REAL problem cars, I have used Honda power steering fluid with excellent 100% results. But only after I fixed the original problem. I had one guy bring back his 55 with the complaint it was too easy to steer. What are you suppose to do about that?
 

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Discussion Starter #20
Just talked to my mechanic. He checked for leaks and/or obstructions in the lines; everything looked great. He really sees no reason why this pump went bad. He's replacing it with a LUK one as we speak...
 
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