I hope it is not to late for you. I had my power steering go out and the resevoir would not hold fluid. After performing on-line research I found pumps for $350 to $600. A call to the local Advanced Auto Parts store found a rebuilt unit in stock for $198 plus a $50 core charge. Once I got it home I found an on-line service manual for about $25 at alldatadiy.com. $25 buys a one year subscription. It did provide the sequence of events to remove the pump. However it does not inform you of certain basic items, such as how to remove the belt or that the idler tension pully must be removed to access one of the pumps torx bolts. It does not tell you that the idler tension pulley has a tamper proof torx head fitting to remove the belt. Leave it to MB to not want to allow you to change your own belt. Discouraged after a trip to find a tamper proof T50 torx bit, I went ahead and removed the resevoir. Remove the engine top cover and one torx bolt (bottom left corner of resevoir), one hose clamp (return line on rear of resevoir) and one clip (resevoir to pump inlet, use thin wide blade screwdriver, place in notch and twist out) and the resevoir slides right out (about 5 to 10 minutes). Have a rag handy for residual fluid. There is an o-ring where the resevoir feeds the pump. This o-ring does not come with the pump. MB sells it over the counter for $2.50 (the next day of course). After a good cleaning and inspection of the resevoir, hose and the pump housing I tried the resevoir to pump o-ring first. Lube the new o-ring in power steering fluid (Dexron III, ATF), slide it on the pumps inlet port, insert the resevoir into its guides and reinstall the torx bolt secring the resevoir to the engine block. This will also push the resevoir in far enough to reinsert the clip that holds the resevoir to the pump. Insert the clip next. I had cleaned all the surfaces and wirebrushed the clip so it would go in easier. Due to the low pressure return line inlet placement it can be tricky to insert the clip. I used a 90 degree needle nose pliers to gain leverage and it slid in the first attempt. Reattach the low pressure hose and your ready to fill the resevoir. Per MB fill the resevoir almost to the top and turn the engine on for about 5 seconds and turn it off, check the fluid level. It should be low. Perform this process 2 or 3 times (I did it 3) before the level stabilized. I filled the level to the top line of the dip stick and started the motor looking for leaks. After a successful leak test I took it on a test drive. MB says to turn the wheel from lock to lock 30 times to push the air out of the system. Fluid may look frothy due to air coming up, mine did. Afterwards recheck your level and you should be good. If your like me return the unused pump. Total repair was $2.50 for the o-ring, $25 for the manual and $5 for fluid. MB uses Automatic Transmission Fluid (ATF) Dexron III for the power steering fluid.
One other thing to check, not found in the manual, the low pressure line runs through a cooler in the radiator. Trace the low pressure line from the resevoir to the radiator and check these connections. My bottom connection had become loose and was abount to come off. MB had a recall on the original hose clamps used at the factory. They may need to be replaced.
Hope this helps others....Good Luck and don't ask MB for advice...They wanted $1,200!!
Great story,
I just replaced everything you mentioned right to the tee. No signs of oil anywhere.
I have a problem with a Mercedes E320, year 2000. It has a stiff/hard to turn steering wheel. I took off the resevoir, cleaned it and replaced the fluid. I also bled the system for air, but there was no change. I have been told that its the power steering pump that needs replacement. There are no leaks anywhere. Can I get the power steering pump checked out for a reasobale cost while its still on the vehicle ? If it is the pump then how difficult is it to replace ? Are there any instructions available anywhere ?
I have a problem with a Mercedes E320, year 2000. It has a stiff/hard to turn steering wheel. I took off the resevoir, cleaned it and replaced the fluid. I also bled the system for air, but there was no change. I have been told that its the power steering pump that needs replacement. There are no leaks anywhere. Can I get the power steering pump checked out for a reasobale cost while its still on the vehicle ? If it is the pump then how difficult is it to replace ? Are there any instructions available anywhere ?
Who was it that told you the P/S pump was bad?
Is the steering hard when parking or at driving speeds or both?
Is the steering hard when cold or hot?
Your system has what is called a P valve; an electrical assist valve that is actuated only when parking. While turning the wheel, is it choppy or is just uniformly hard to turn?
All of these things have to be considered before condemning the pump.
Checking to see what the correct pressure is requires a special tool and I doubt even M/B would have it or even if they did, bother to do the test.
Before investing in a P/S pump, raise the front end off the ground and see if the turning is remarkably different. If not remove both tie rod ends and see if there is a difference. If there is a marked difference then by hand turn each steering knuckle an see if there is any restriction, if not it is PROBABLY the pump. If not, it could be the rack and pinion/steering rack.
Also, you should try a 50mm bottle of Lubrizol (purchased at dealer) before buying a pump. Try that first for a few days and see if it helps.
Here are the instructions for removal, but I would do some tests before absorbing the cost.
Thank you for the complete and detailed response. My steering is hard to turn in both directions at low speeds ( i.e parking). The fluid level is as required and there are no leaks. I will try the Lubrizol solution first. An independent MB mechanic observed the hard steering and suggested changing the pump without any other diagnostics. There was no pressure tests done. Perhaps I need to show it to another mechanic to get a second opinion.
If it comes down to the steering pump, keep in mind that a good experienced Mercedes mechanic could rebuild the exisiting one by using commercially available ps rebuild kits. That would probably cost you the least amount of money.
I have had the Lubrizol in the steering fluid resevoir for about a week now without any noticable easing of the steering stiffness. What practical diagnostics could be done to determine if the pump, rack or something else is at fault. It seems that the only way to test the pump requires special equipment not generally available. I guess changing the pump is cheaper than the rack, but it would be nice to be sure.
43sqd, do you by chance have a drawing of ML320 PS and components or is it the same as in E320? My power steering has gone yesterday on the motorway following some deep mud offroading. The car has bottomed on a few of occasions but I didn't have a chance to get under the car yet and wanted to get some guidance. thank you.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
Linear Mode
