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post #1 of 2 (permalink) Old 01-05-2009, 05:13 AM Thread Starter
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Date registered: Jan 2009
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Who can giver me instructions on How to replace the power steering pump reservoir on a 2003 Mercedes ML320?
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post #2 of 2 (permalink) Old 02-18-2009, 05:33 AM
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Replace ML320 Power steering Pump

Have fresh power steering fluid available. Quick warning - DO NOT USE - Pentosin oil. This oil foams and will cause noise. I used it, and had to drain it. Ideally, drain out old fluid and replace with Benz fluid.
Buy 2 bottles from Mr. dealer.
Obtain a Steering Pulley puller (About $30.00 + tax to rent from Autozone – You’ll get a refund when you return it)
New or refurbished power steering pump (Usually comes with the supply line seal)
A quality 7mm torx (Same as brake caliper tool)
Torx socket Wrenches etc

Use a suction syringe to drain old fluid from the reservoir.
Disconnect 2 hoses; one on the reservoir, the other on the pump itself.
Remove a large C clip holding the reservoir supply end to the pump. Use a flat head plier in combo with a flat head screw driver (Careful not to crack the container)
Remove the reservoir unit. (If in doubt, quick low pressure test will confirm if cracked or not)
There's a small seal between the reservoir and the pump - NEVER RE-USE ANY old SEAL - Get a new one from the dealer (usually $1.50 - $2.70). Some big bucks dealers like Inskip - in RI charge $4.50 plus tax.

If necessary, draw the serpentine belt routing diagram on a piece of paper before removal it may confuse newbies.

The bolts holding the pump in place from behind are different in length so note what comes out of where.
With a 17mm socket wrench on right hand, carefully but firmly lift belt tensioner up and take off belt from the top most pulley with your left hand. (Tensioner relieve bolt is obscured by the belt but you'll find it a bit to your left side of the tensioner - closer to the Main bearing pulley.

Using the Torx socket, unscrew 2 torx bolts from back of pump (1 at about 7 o'clock the other at about 10 o'clock)
Use the 7mm torx on the bolts in front. (A bit obscured; top one is at about 10 o'clock and the lower one at about 6 o'clock. Reach these bolts through the slots in the pump pulley.

Once pump is out, use the puller to remove the pulley from the old pump, install the pulley on the new pump (You don’t need this step if you got a new pump & pulley assy - usually a $100.00 or more expensive).
Re-install entire assy, making sure you hand tighten all 4 bolts as close as possible. Keep each bolt snug enough to allow all 4 bolts in before wrenching tight. Do not force any bolt into place as this can easily become much more expensive if you strip any bolt due to improper alignment.

Install new seal on pump inlet, re-install the reservoir, replace C clip (New C clip - I reused mine) Attach the hoses ensuring a new seal is in place on the high side hose lip.
Fill reservoir with fresh fluid, do not cover yet. Put serpentine belt back, remove all tools from work area.

To eliminate air in system, I didn’t have M-Benz recommendations on this job, but here’s what I did. Bleeding comes with luck sometimes. I got away with some crazy U turn tricks, but you might be better off with this guys advice. Said he has done 3 - must have something good going.
If you get stuck and have to leave this job overnight wrap hoses mouth with some plastic cover to reduce moisture absorption.

Okay folks, good luck on your projects. This one is quite EZ. Apart from my labor, entire job cost me about $180.00, took about 3hrs could have been less and that includes 2 well chilled bottles of Guinness. Inskip dealership, humn! They want $799.25 + tax for pump assy; who knows what labor will be? Oh!, no Irish booze benefits either - Can't blame them for high charges though, someone's got to pay for those shinny floors, fancy counter tops and yes, they even let you drool over those new S-Class - after all they are only catering to our taste and affluence – One of the very few good things about a M-Benz is the high probability of surviving a serious accident; but then who can put a definite determination on accident survival? Science or God.


Last edited by Richy Lawmn; 02-22-2009 at 06:27 AM. Reason: Improved advice
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