arcaidy

I had to replace the steering rack on my ML55 and before I started I looked here and a few other forums for a how to. I was unable able to find any complete directions from start to finish.

Knowing what I know now I could have saved myself around 2 hours… I figured I’d pass my info on to anyone else considering doing their own.

Disclaimer:
I’m a DIY’er, not a mechanic. This is how I performed the work. Your mileage may vary. You’ll have to forgive me if my terminology is incorrect.



1. You WILL need to remove the front drive unit. This is not a bad thing. I would have saved myself a significant amount of time had I done this first.

2. This is a good time to remove the tie rods. Remove the nut and tap the unit until it frees.

3. You will need to remove the axels. To do this you will need to disconnect the spindles. This is the hunk of metal the rotors and caliper connect to. There are two nuts holding this on. One on the top and one on the bottom where the unit pivots. Before unbolting these, you will need to remove the large nut securing the axel. On a ML55 is 34mm in size. You will need a large breaker bar or impact to remove this. Once removed I used a hammer to free the axel. I leave the nut on and flush with the bolt so I don’t mess up the threads. Now remove the two nuts mentioned above. Lightly tapping the metal around the bolts helped free them once the bolts were removed. Pulling straight out on the axel will pop it out of the drive unit. They are kind of heavy so make sure you have a firm grip so one end doesn’t fall on the ground.

4. Place a jack under the unit to hold it up. There are 2 bolts and 1 nut and bolt combination holding the front drive unit in. There are 8 hex bolts connecting the front drive shaft to the unit. The two bolts on the front are easy to remove. The nut and bolt on the rear is a little more difficult because of space. The 8 bolts on the drive shaft are a bit of a pain because there isn’t space to use a socket. There is a breather hose on the front/top/right. Mine was brittle and broke when I removed it. Drop the unity down from the front and slide out.

5. Now you have plenty of room to work on the steering rack. There are two nuts and bolts that secure the unit to the frame. There is one electrical connection and two hydraulic lines. There are two nuts and bolts on the universal connecting the steering shaft. I removed the driver’s wheel well cover, and rear exhaust heat shield to give me better access. This helped when putting things back together and only took a few minutes to remove and replace. Unbolt/disconnect everything and pull the unit out.

6. I reused my tie rods because there was nothing wrong with them and they were easy to remove from the old unit. You may choose to use new one. Either way, make a note on the number of threads viewable. This will help you get the alignment close to what it was when you removed it. You’ll need an alignment once you’re complete, but this should get things close to what they were while you waiting.

7. Check your unit and make sure it matches the part you ordered. Some places won’t accept a return if you attempted to put it in before you send/take it back.

8. Install the new rack. I had to slide mine in from the right to get it to fit. There wasn’t enough room to slide it from front to back. I placed to the right of the brackets and slid to the left and then bolted it up. You may want to connect the steering column linkage first. I’m not sure which is best. I did this step last and it was a little trouble some, but I’m not sure if I would have been able to bolt the rack in had I done this first. Make sure your steering wheel is centered. Next measue the steering rack ends to make sure they are the same length on both sides. The shop doing the front wheel alignment can correct some centering issues, but there isn't a lot of room for correction on my car so you will need to be close when connecting the steering column linkage to the steering rack. Next, There are two power steering hoses to connect. Be careful here. You should be able to tighten these down flush with your hand. If you strip these you are SOL and must order a new rack which you’ll probably have to pay full price for again…. There are 2 copper gaskets for each line/bolt. I reused mine, but would have purchased new ones had I known I needed them. You may want to leave the top line loose until you get the front drive unit back in. I had to loosen my back up to make room for the drive unit and then tighten it back down. Reconnect the electrical connection.

9. Reinstall the front drive unit the same way you took it out. The axel will need a little force but will pop back in. This is a good time to change the lubrication in the drive unit. I wish I have thought it through and done this… Reconnect the axel to the front spindle units. Now reconnect the front spindle units. You will need a hex and torx bits to hold the bolts steady or the will turn with the nut when tightening.

10. Connect the Tie Rods to the steering rack. Place then at the same lengths they were on they old unit. Secure them to the spindle. You will need to use a torx bit again here.

11. Next is the information included with the steering rack. Yours may be different. With the front wheels off the ground, turn the steering wheel to full left. Fill the power steering pump reservoir to the cold full line. Turn the steering wheel to full right then full left 20 times. Check fluid levels and fill as needed. If additional fluid was needed, repeat the steering wheel turns. There should be no bubbles. Next start the car and turn the wheel. The directions say there should be no noise, but I had noise. It also said there should be no bubbles but I had bubbles… They said bubbles could be a sign of leak in the system. About this time my neighbor stopped by and I turned off the car and chatted with him for about 15 minutes. I then restarted the car and the sound was almost gone. I looked and the bubble were gone, but I was low on fluid. I added some more fluid and then test drove the car. At higher speeds I could hear the power steering “whine”. I got home and found some more bubbles in the reservoir, but not near as many.

I took the care to the store about 4 hours later and now hear no noise. I don’t know if it takes a while for all the air in the system to come up, or if I didn’t turn the wheel enough to get it all out. Everything thing seems fine now though. I will say the car as a whole drive much better. The steering rack much have been having problem for a while, because there is a big difference in what there was and what it is now.

All together it took me about 6-8 hours combined time. I think if I had dropped the front drive unit first my time would have been in the 3-5 hour range. I’m pretty sure I could do it now in less than 3 hours.

I’d categorize this as a moderate level of maintenance. Mainly because of the tools needed to remove the front axel. The rest is fairly straight forward. If you have an impact wrench, you can remove the front axel bolt without any problem. You could easily buy the tools needed with the money you save by doing this yourself. I usually end up buying a few tools each time I work on my cars, but it’s still cheaper than having someone else do it and I get to keep the tools when I’m done.

I paid $590 for the steering rack with next day shipping, a return shipping label to return the core, and a 3 year unlimited mileage warranty. Core was $250. I spent $200 in tools because I bought myself a new air compressor and a 34mm impact socket.
I found the steering rack cheaper, but wanted to go with someone known. I placed an order with the benz bin but had the cancel the order after waiting over a week from the rack after I ordered it. They said they had it in stock but refused to tell me if it had been shipped or not after a week of waiting… I had to cancel that order and went with www.mercedessteering.com. Jim called the warehouse and had them physically check for a core before he let me order. He then had it rebuilt and at my door by 2pm the next day.

Hope this might prove helpful to someone else later down the road. I apologize if I left anything out or named a part wrong.


So far I have replaced a motor mount, MAF, power steering pump seal, steering rack, and window switch in my car.
2001 ML55 with 118k miles.

azinn

Good job...................... you must have saved a ton of $$$$$$$$$$$$

MercMuzz

hey guys, had a power steer leak coming from the rack where the high and low pressure hoses join the rack. I have had the power steering resevior recall performed so I knew it wasn't that.

I thought i would check the tension of the torx bolts before I went and got any further advice. You wouldn't believe it, the top bolt was very loose. I simply used a 15mm socket and ratchet to tighten it up and no more leaks......Hope this helps someone....you may not have to replace the rack after all and save a heap of money

Muzz

hacki

Thanks for the tip!
I'm have to replace my steering rack and now i know how much time it will consume.
I have no probs to do the work more than i'm in "the blue hall" to do my work here in Sweden.
I have to admit that i really love my ML55 AMG (don't tell my girlfriend)!
There is another thing: once upon a time there was some ROOT compressor kit that would fit this engine(mine is a 2001), is there any possibility to find it nowadays? Could be a surprice for these Toyota Supra guys here in Västerås, Sweden!
PS: Blue hall is outside...no roof...
//hhacki

erickonphoenix

Hey @arcaidy, Thanks for the writeup. I just replaced my mom's steering rack on her ML500 and your write up was a big help.

Here's a supplemental write up for Steering Rack replacement on a Mercedes ML500. I'm adding it to this thread because this is the first thread anyone will find searching for DIY's on the steering rack replacement on a Mercedes ML. Be advised working on your own vehicle can be a hazardous undertaking if you don’t understand how to safely jack and stabilize a vehicle on jack stands seek professional help.

I’ve got a good inventory of tools and some mechanical experience so I would rate this as an intermediate service that can be performed by anyone with basic mechanical skills and a good set of hand tools. This service took me about 8 hours to perform. I spent 4 hours Saturday and another 4 hours Sunday.

Tools I used:
3 ton hydraulic jack
4 ton jack stands
Wheel chocks
Impact driver,
Set of metric sockets and drivers with extensions
Torx socket set
Allen wrench kit
I did use a pickle fork to release the tie rod from the wheel hub but it’s not necessary if you want to retain the old tie rods.

My Mom's 04 ML500 is the V8 All wheel drive one with 130k miles and is in excellent condition. Since this ML is AWD the front differential needs to come out to get to the rack, But per the OPs post, it's not complicated to drop it.

1. First off raise the vehicle and remove the front tires. You'll need to remove the drivers side wheel well cover, and you'll see a metal access panel to the steering coupling. All the nuts from the wheel well cover to the steering coupler access panel was 10 mm.

NOTE: When you’re working on jackstands I always push the wheels under the vehicle just behind the jack stands. That way in unlikely event you have a jack failure at least the vehicle will only fall down to the width of the tires. You’ll be spending a lot of time under the vehicle and that piece of mind nice to have.

2. I was able to pull out the axels on the ML500 by just detaching the upper control arm from the both front wheel hubs. The ML55 may be different but the ML500 can do it by just detaching the upper control arm. Then I zip tied the wheel hub up to the upper control arm so the brake lines weren’t under stress but the axels were free from the front differential.

3. Support the front differential with a floor jack. I happen to have a cradle attachment but if you don’t you can have a friend stabilize the diff while you lower it later.

NOTE: The front diff had a vent hose on it which I broke off because I didn't know it was there. However, $6 worth of vacumm hose and I was back in business. But if you know it's there you can detach it from it's bracket next to the window fluid reservoir. It's down on the lower left if you are facing the tank from the front of the vehicle. Also, go ahead and drain the front diff. You’ll lose practically all the fluid in the removal anyway.

4. The propellor shaft on the front drive unit was attached by six bolts. These came out slowly because of the thread lock the factory uses. 
NOTE: Put the vehicle in Neutral and you can spin the shaft for better access to the bolts. Then put it back in Park when you loosen or tighten the bolts so the shaft will be fixed and not spin on you. I didn’t have to support the shaft, it reseted on a cross member pretty level so I left it in place.

5. The two front diff mounting bolts are cake, they come right out. The rear diff mounting bolt is set perpendicular to the frame and is easily accessed however tight quarters make moving a ratchet a challenge. So I found alternatively this bolt can also be accessed through the passenger wheel well with a 24” long extension (or a combination of extensions that get you up to about 24”.) Get a friend to back the nut on the drivers side then using an impact drill you can drive the bolt out in seconds.

6. Remove the tie rod ends where they connect to the steering knuckle on the wheel hub.

7. The steering coupling was 15 mm. I removed the coupling from the steering wheel shaft and left it attached to the rack thinking I would center it on the work bench.

8. Remove the two banjo bolts that connect the hydraulic lines to the rack. (have a bucket ready)

9. Remove the two mounting bolts for the rack. Interestingly mine were mounted bolt down on the driver side and bolt up on the passenger side. (This ML500 did not have an electrical connection to the steering rack)

10. Then I removed the rack through the passenger wheel well. I was able to do this without removing the passenger wheel well cover. Play with articulating the steering coupler and it will go or just remove the steering coupler all together before you take the rack out.

11. With the rack on a work bench, I replaced the tie rods by counting the exposed threads and installing the new ones' to that position. The locking rings loosen by turning them clockwise.

NOTE: The new rack had two arrows that looked like they were for clocking the steering spline with the center position on the rack but apparently that was not the case. So I opted to pull the coupler off on the bench and align the steering when the rack was mounted back in the vehicle. I still don't know what those arrows were for. Chime in if anyone else knows. Also, be sure to buy the four crush washers that go on the banjo bolts that connect the hydraulic lines to the rack. I had a couple day wait for these to come in on order. Apparently Mercedes parts don’t keep a lot of these in stock.

Installation was reverse of removal. ADDITIONAL NOTES:

To find center on the steering coupler, I loosely mounted the rack in the vehicle and pushed and pulled the tied rod ends until it measured 5 9/16” extension from the inboard side of the dust boot to the beginning of the threads for the tie rod and called that center. However, you could measure from the in board side of the dust boot to anywhere as long as the measurement is the same on both sides, then your rack should be centered.

1. I had a friend center the steering wheel from the drivers seat while I mounted the coupler to the steer wheel shaft and tightened it.
2. Next, Since you don’t have room to put the coupler on the rack with it mounted in place, I carefully unmounted the rack, slide it forward and installed the bottom of the coupler to the rack's steering spline.
3. Then I remounted the rack and tightened up the couplers lower bolt. I used 28Nm of torque on both bolts and medium thread lock. However the connection is positive so even if the bolts were removed the coupler could not disconnect from the rack. Hence the reason I had to mount, measure, unmount, then attach the coupler before mounting again. Mercedes designed it to be idiot proof.

When reinstalling the front drive shafts, you can reach under the vehicle and rock the drive shaft by hand until one slides in then go around and do the other side. They act stubborn at first but once you’re in they will pop right into place.

You’ll need to refill the front diff with Mercedes fluid and recharge the power steering system. That process is outlined everywhere so I’ll skip it here.

Everything else was pretty straight forward. Biggest thing on the AWD version is committing to removing the front drive unit. Saves time and frustration. When I was done we took a five mile test loop at highway speed and everything was functioning as designed and the steering was straight and centered. I directed my mom to take the vehicle in for an alignment after which I’ll call it done.

In addition to this thread I also found good diagrams and info here:
http://www.benzworld.org/forums/w163...que-specs.html

Torque figs I used were…

Front drive mounting bolts 50 Nm
Front drive drain and fill plugs 10Nm

Steering rack mounting bolts 50 Nm
Steering rack banjo bolts 30 Nm
Steering coupler mounting bolts 28 Nm

Tie rod connection to steering knuckle 55 Nm
Upper control arm to rotor 55 Nm

anavabi

I know it's been a while, but do you remember the reason why you ended up changing the rack and pinion. What were the symptoms?

erickonphoenix

No worries @anavabi The first indication was a slow hydraulic leak at the driver side rod seal. That leak escalated slowly over time along with a high pitched whine when the steering rack was put under load. When the rack failed completely there was a massive fluid spill and the wheel became very difficult to turn.

Hope that answers you Q.

anavabi

Thanks. I have the same symptoms except the leakage. There's no apparent leaks but only stiff steering when engine is warmed up.

erickonphoenix

Have you checked your fluid level? It could just be low?

anavabi

The fluid level is fine. It's become a mystery for me.

erickonphoenix

There's a power steering pump that pumps fluid into the rack. That could be dysfunctional. To check that I'll do one of two things. Lift the nose up then put a mechanics stethoscope on the pump and listen for any change in tone. The other way is pop off the send hose and see if it's ejecting fluid. (that's the lazy way). One way or another I think you're going to be lifting the front end up and crawling under there while a friend articulates the wheel.

anavabi

Thanks.
Don't mind the crawl at all. However, would you please explain the reason for lifting front for this check.
Also, what should I be looking for under the car. I've noticed the lines to rack and pinion dance a bit while the wheel is turning. What is the alternative to the "lazy" option. Don't mind getting dirty. I enjoy working around cars, though lots of frustration at times!
Thanks

anavabi

I know it's been a while, but during the replacement, you're supposed to make sure steering wheel does not move at all. What did you do for this.
Thanks,

hacki

anavabi:
In slow speeds it was hard to turn the steering wheel and it was leaking
There is a valve on the rack which changes pressure in two positions, high pressure at parking and low pressure driving in high speeds and this functiondid not work at all.
And vehicle inspection did not like it...dripping oil all the time!


//hacki

flyingsquirrel

[QUOTE=Hey @arcaidy, Thanks for the writeup. I just replaced my mom's steering rack on her ML500 and your write up was a big help.
NOTE: The new rack had two arrows that looked like they were for clocking the steering spline with the center position on the rack but apparently that was not the case. So I opted to pull the coupler off on the bench and align the steering when the rack was mounted back in the vehicle. I still don't know what those arrows were for. Chime in if anyone else knows. e[/QUOTE]

I know this is an old thread, but I am incredibly grateful for the contributions. This was a difficult job for me, it took four days working a few hours each day. I was also able to get the axles out of the diff by removing just the upper control arm ball joint. Thanks for the tip about the differential vent tube, I was able to awkwardly lower the differential by myself with a floor jack, and thankful I had a helper to operate the jack for me when it went back in.
My biggest challenge was getting the rack off the steering column. I stupidly went after the splined end of the U-joint, 45 minutes of prying and yanking later, I realized I could easily use a screwdriver to pry the the upper end and slide it off easily. It made it more difficult to wiggle the rack through the passenger side with the U-joint still attached but was necessary.
As far as the arrow on the rack goes, Before removal I centered the steering wheel and marked the relation of the U-joint to the arrow. I made sure the replacement rack was centered and careful replaced the U-joint on the bench with the marks lined up and it slid right into the steering column upon re-assembly.
Thanks again for all of the advice, It made a difficult job possible for me.
Edit: My replacement rack immediately leaked at the pinion seal at the steering shaft. Oh Joy! I got to do the job twice, the parts store honored the warranty and I got the new one in in half the time. Now the steering is tight and straight with no leaks!

ErkanG

Hi. Could you tell me where that breather hose attaches to? Mine is dangling down from the rack. I just can’t figure our where it goes.. thanks!

QUOTE=arcaidy;2127508]I had to replace the steering rack on my ML55 and before I started I looked here and a few other forums for a how to. I was unable able to find any complete directions from start to finish.

Knowing what I know now I could have saved myself around 2 hours… I figured I’d pass my info on to anyone else considering doing their own.

Disclaimer:
I’m a DIY’er, not a mechanic. This is how I performed the work. Your mileage may vary. You’ll have to forgive me if my terminology is incorrect.



1. You WILL need to remove the front drive unit. This is not a bad thing. I would have saved myself a significant amount of time had I done this first.

2. This is a good time to remove the tie rods. Remove the nut and tap the unit until it frees.

3. You will need to remove the axels. To do this you will need to disconnect the spindles. This is the hunk of metal the rotors and caliper connect to. There are two nuts holding this on. One on the top and one on the bottom where the unit pivots. Before unbolting these, you will need to remove the large nut securing the axel. On a ML55 is 34mm in size. You will need a large breaker bar or impact to remove this. Once removed I used a hammer to free the axel. I leave the nut on and flush with the bolt so I don’t mess up the threads. Now remove the two nuts mentioned above. Lightly tapping the metal around the bolts helped free them once the bolts were removed. Pulling straight out on the axel will pop it out of the drive unit. They are kind of heavy so make sure you have a firm grip so one end doesn’t fall on the ground.

4. Place a jack under the unit to hold it up. There are 2 bolts and 1 nut and bolt combination holding the front drive unit in. There are 8 hex bolts connecting the front drive shaft to the unit. The two bolts on the front are easy to remove. The nut and bolt on the rear is a little more difficult because of space. The 8 bolts on the drive shaft are a bit of a pain because there isn’t space to use a socket. There is a breather hose on the front/top/right. Mine was brittle and broke when I removed it. Drop the unity down from the front and slide out.

5. Now you have plenty of room to work on the steering rack. There are two nuts and bolts that secure the unit to the frame. There is one electrical connection and two hydraulic lines. There are two nuts and bolts on the universal connecting the steering shaft. I removed the driver’s wheel well cover, and rear exhaust heat shield to give me better access. This helped when putting things back together and only took a few minutes to remove and replace. Unbolt/disconnect everything and pull the unit out.

6. I reused my tie rods because there was nothing wrong with them and they were easy to remove from the old unit. You may choose to use new one. Either way, make a note on the number of threads viewable. This will help you get the alignment close to what it was when you removed it. You’ll need an alignment once you’re complete, but this should get things close to what they were while you waiting.

7. Check your unit and make sure it matches the part you ordered. Some places won’t accept a return if you attempted to put it in before you send/take it back.

8. Install the new rack. I had to slide mine in from the right to get it to fit. There wasn’t enough room to slide it from front to back. I placed to the right of the brackets and slid to the left and then bolted it up. You may want to connect the steering column linkage first. I’m not sure which is best. I did this step last and it was a little trouble some, but I’m not sure if I would have been able to bolt the rack in had I done this first. Make sure your steering wheel is centered. Next measue the steering rack ends to make sure they are the same length on both sides. The shop doing the front wheel alignment can correct some centering issues, but there isn't a lot of room for correction on my car so you will need to be close when connecting the steering column linkage to the steering rack. Next, There are two power steering hoses to connect. Be careful here. You should be able to tighten these down flush with your hand. If you strip these you are SOL and must order a new rack which you’ll probably have to pay full price for again…. There are 2 copper gaskets for each line/bolt. I reused mine, but would have purchased new ones had I known I needed them. You may want to leave the top line loose until you get the front drive unit back in. I had to loosen my back up to make room for the drive unit and then tighten it back down. Reconnect the electrical connection.

9. Reinstall the front drive unit the same way you took it out. The axel will need a little force but will pop back in. This is a good time to change the lubrication in the drive unit. I wish I have thought it through and done this… Reconnect the axel to the front spindle units. Now reconnect the front spindle units. You will need a hex and torx bits to hold the bolts steady or the will turn with the nut when tightening.

10. Connect the Tie Rods to the steering rack. Place then at the same lengths they were on they old unit. Secure them to the spindle. You will need to use a torx bit again here.

11. Next is the information included with the steering rack. Yours may be different. With the front wheels off the ground, turn the steering wheel to full left. Fill the power steering pump reservoir to the cold full line. Turn the steering wheel to full right then full left 20 times. Check fluid levels and fill as needed. If additional fluid was needed, repeat the steering wheel turns. There should be no bubbles. Next start the car and turn the wheel. The directions say there should be no noise, but I had noise. It also said there should be no bubbles but I had bubbles… They said bubbles could be a sign of leak in the system. About this time my neighbor stopped by and I turned off the car and chatted with him for about 15 minutes. I then restarted the car and the sound was almost gone. I looked and the bubble were gone, but I was low on fluid. I added some more fluid and then test drove the car. At higher speeds I could hear the power steering “whine”. I got home and found some more bubbles in the reservoir, but not near as many.

I took the care to the store about 4 hours later and now hear no noise. I don’t know if it takes a while for all the air in the system to come up, or if I didn’t turn the wheel enough to get it all out. Everything thing seems fine now though. I will say the car as a whole drive much better. The steering rack much have been having problem for a while, because there is a big difference in what there was and what it is now.

All together it took me about 6-8 hours combined time. I think if I had dropped the front drive unit first my time would have been in the 3-5 hour range. I’m pretty sure I could do it now in less than 3 hours.

I’d categorize this as a moderate level of maintenance. Mainly because of the tools needed to remove the front axel. The rest is fairly straight forward. If you have an impact wrench, you can remove the front axel bolt without any problem. You could easily buy the tools needed with the money you save by doing this yourself. I usually end up buying a few tools each time I work on my cars, but it’s still cheaper than having someone else do it and I get to keep the tools when I’m done.

I paid $590 for the steering rack with next day shipping, a return shipping label to return the core, and a 3 year unlimited mileage warranty. Core was $250. I spent $200 in tools because I bought myself a new air compressor and a 34mm impact socket.
I found the steering rack cheaper, but wanted to go with someone known. I placed an order with the benz bin but had the cancel the order after waiting over a week from the rack after I ordered it. They said they had it in stock but refused to tell me if it had been shipped or not after a week of waiting… I had to cancel that order and went with www.mercedessteering.com. Jim called the warehouse and had them physically check for a core before he let me order. He then had it rebuilt and at my door by 2pm the next day.

Hope this might prove helpful to someone else later down the road. I apologize if I left anything out or named a part wrong.


So far I have replaced a motor mount, MAF, power steering pump seal, steering rack, and window switch in my car.
2001 ML55 with 118k miles.[/QUOTE]