My Power Steering Pump Rebuild Thread

[sshanky]

Hi guys,

I'm going to try to rebuild some power steering pumps. I have a w116 that had a leaky pump, and after one bad one, I found one leak-free one last year. However, it's starting to leak, probably from the back seal. In the garage, I have two pumps. I have the front seal and the seal kit, so I'll start with the 82 bar one, which I'll put into the 300SD, replacing the Vickers that's in there. Then, maybe I'll rebuild that Vickers and sell it.

here is the first one I'll work on, the older leaking one from the 300SD (82 bar) before power washing:


and one from a 300D (65 bar). Here are both of them after power washing:

The silver one is the 65 bar and the dark one is the 82 bar.

Here are the pulleys (the one on the right came off the 82 bar, but I can tell that if I use that one it will not line up with the current belt in the car, so I think I will need to use the other pulley, or else the one that's currently in the car:


Here is the 65 bar ZF pump:
v

And Here is the 82 bar ZF pump that I'm going to try to rebuild:


I'll post more later. Any thoughts would be appreciated!

[sshanky]

This morning, I used a clamp to squeeze the big metal disc inward, so I could remove the wire clamp:


The clip and disc removed:


And there was one o-ring. I am not sure if there should have been two, since there are two grooves:


Then I started on the front seal, first by removing the Woodruff Key:


But then I didn't know what to do. I'd read about taking out the innards of the pump, and how there are vanes that have to be kept in place or else they'll be really hard to put back in, but I was prepared and started trying to get the back of the impeller area out so I could push the shaft in and get access to the seal. It seemed that to get the shaft and impeller out, I needed to remove this hex nut:


But it wouldn't budge. I decided not to push it and decided to stop at my friends at Star Service in Tempe.

Meanwhile, I worked on the reservoir area. I just pulled out this clip carefully with pliers:


and removed the spring and stuff beneath it, down to the filter, which was interestingly just a ring of something between two metal plates:






I later took the pump to Star Service, and they took out the seal for me without having to remove the back end at all. Thanks! Now I will go and continue. More pictures on their way...

[engatwork]

Did you have to use a puller on the power steering pump pulley hub?

[Yak]

RE: the third pic in post #2. That plate should come out from the rear. It's a very snug fit since there is another o-ring in there. I used needle nose pliers and wiggled it free. Behind that are the vanes. They're directional: rounded on one face, square on another. They may fall out, but they're easy to put back in. Just check the directionality carefully.

I think other groove you're asking about is for the wire locking ring from pic 1 to rest in, not another o-ring.

[sshanky]

Originally Posted by engatwork

Did you have to use a puller on the power steering pump pulley hub?

No. I was pretty lucky. It was not too tight and it came off easily.

[sshanky]

Originally Posted by Yak

RE: the third pic in post #2. That plate should come out from the rear. It's a very snug fit since there is another o-ring in there. I used needle nose pliers and wiggled it free. Behind that are the vanes. They're directional: rounded on one face, square on another. They may fall out, but they're easy to put back in. Just check the directionality carefully.

I think other groove you're asking about is for the wire locking ring from pic 1 to rest in, not another o-ring.

Haha, you're right about the grooves. I am not sure how I missed that. funny.

Regarding the back plate, I tried to move it but it seemed very snug, and then I assumed (maybe incorrectly, I don't know yet) that the 7mm or 7.5mm hex nut on the outside next to the edge of that plate needed to be loosened to release the plate, but I couldn't get the nut to budge. I got close to stripping the hole and gave up, went to my shop, and there they told me not to bother, and he knocked the seal up for me from the front. Read on for the rest of the story.

[sshanky]

OK, here we go! Here is the front seal after the guy at the shop knocked it out with his screwdriver:

There is a small nick in the metal but I plan to smear a thin layer of some gasket silicone around the new seal before I put it in, and the nick doesn't go down too far.

Here's what you see when the seal is pulled out:

The metal disc you can see there lifts right out, revealing a bearing. I dropped it right back in and left it alone. I carefully felt the surface of the shaft where it contacts the front seal, and it felt very smooth and clean. I cleaned it as well. I think some people use a very fine type of sandpaper or abrasive to smooth it even more (the diesel giant kit comes with some "paper") but I didn't go that far.

Here are the two seals side by side, front and back:


I can see a small gap on the backside of the old one -- I don't know if it's supposed to be there, or if it's a crack that could have leaked. This pump was filthy and I think it leaked on the front side.

Anyway, let's move on and put in the new front seal. I took some of my black gasket silicone material (I was told to use another type of stuff that turns harder but didn't have it and got impatient) and put a very thin smooth layer of it all around the outer edge of the seal. Then, I put the seal in placed and pushed, and it went in quite smoothly and easily. I used a round closed wrench end to place flat over it and tap it in further. It looks pretty good:


Don't forget to put the Woodruff key back in:



Now let's move on to the back side. Here is the seal kit:


I used the large o-ring and replaced it in the back groove. I smeared some lubricant the guys gave me on the ring and on the edges of the metal disc. I cleaned the groove and then placed the o-ring (easy) and then the spring and the disc, pushed them in, used my clamp to hold them in, put back the metal retaining ring, and then released the clamp. This part was easy and I didn't bother to take photos.

Now, I moved on to a difficult part. The large hex nut I assume is for a relief valve and I could see a copper ring similar to one in my seal kit so I had to at least replace that and see if I could clean anything in there. I had a lot of trouble getting the nut loose. Even with my biggest adjustable wrench (pretty big) I couldn't get it. So I drove over to Autozone and got a big 1-13/16" socket (they didn't have 30mm):

and used my 1/2" breaker bar to get it off:

Be careful here, the spring could cause the nut to fly off if you're not holding it.

Here it is with the spring out:


and with the oil out:


This part pulls out:


Here it is, with the spring and the nut:


The nut on the end of this unscrews, and there's a spring inside. Here's a slighly clearer image:

Not sure what it does, and mine looked clean so I didn't want to bite off more than I could chew, so I left it alone and replaced it. I made sure the piece slides up and down smoothly and easily.

Next step, clean out the place where the copper washer sits, and clean the bolt, especially the part that will contact the copper washer, and replace:


And that's it! Here is the pump, all good as new:


I replaced it in the car, started it, bled the pump, lifted the front wheels off the ground, put in some ATF, started the car, watched the fluid go down into the pump, added more ATF, turned the wheels some more, lowered the car, turned the wheels again, then closed it all up, and hopefully got all the air out.

I just power washed the hood and I'll try to get you a few shots of it in place. Any questions, feel free to ask. I do have two pumps that I may rebuild and try to sell. If interested let me know.

[Renntag]

Nice write up. My pumps seem to be in good shape but I should consider replacing a hose. I havnt replaced the filter and am not quite sure how to go about it.

Is ATF the prefered fluid or just a good substitute after a full system rebuild?

[Stretch]

Holy moly

it is just like being on Benz World!

My Power Steering Pump Rebuild Thread - Benzworld.org - Mercedes-Benz Discussion Forum

I forgot where I was for a minute!

[sshanky]

You can find a filter cheap online, or 12 bucks at an auto parts store. There are some writeups on how to flush your power steering system. When you empty the fluid, you'll see the filter under the cover. You have to pull off the little clip with pliers, then remove the spring, then take out the filter, which may be one piece (like the new ones) or three pieces (see my photos above). You replace the filter, holes up, spring back in, push clip on, then place the cap back on to push the clip down.

As for fluid, most people seem to agree Dextron III (ATF) is the right thing to use. I got conflicting reports on which one would make the seals get hard or not, but most people say ATF.

To bleed the air out of the system after you put new fluid in, you lift the front wheels off the ground, start it, make sure the reservoir doesn't completely empty, and turn the steering wheel all the way in both directions a few times. that should get the air out. then put a little more fluid in so it's not too low, and replace the cap.

Good luck! It's not too hard!

[sshanky]

Originally Posted by Army

Holy moly

it is just like being on Benz World!

My Power Steering Pump Rebuild Thread - Benzworld.org - Mercedes-Benz Discussion Forum

I forgot where I was for a minute!

Wasn't that nice of me to post it on both forums?

[Stretch]

Originally Posted by sshanky

Wasn't that nice of me to post it on both forums?

You're great mate!

Also I think you'll find most people think Dexron II is alright for the age of the car (not 3).

[sshanky]

I once read that transmission fluid had some stickiness or some other quality that makes it suitable to transfer the torque, and it said that property might be bad for a power steering system. Most other people said it's fine, though. Another guy told me that actual PS fluid will hurt the seals more than the ATF will. I got confused as well when I tried to find the actual Dextron III substitute, since there are lots of Dextrons. What's the difference between them? I don't really know much about the fluids.

Thanks

[Stretch]

Originally Posted by sshanky

I once read that transmission fluid had some stickiness or some other quality that makes it suitable to transfer the torque, and it said that property might be bad for a power steering system. Most other people said it's fine, though. Another guy told me that actual PS fluid will hurt the seals more than the ATF will. I got confused as well when I tried to find the actual Dextron III substitute, since there are lots of Dextrons. What's the difference between them? I don't really know much about the fluids.

Thanks

I don't know much either.

My usual source for information isn't very good today

DEXRON - Wikipedia, the free encyclopedia

From what I can make out in the USA dedicated power steering fluid seems to be widely available. Over here it isn't. I read all of the warnings and fuss on this forum about only using power steering fluid and I couldn't find the bloody stuff for sale over here. So I consulted several good quality oil manufacturers' web sites and found that they all stated that their dexron 2 should be used in the power steering. So I've been using that!

[cp361]

Thanks for the thread ..I just notice some tell tale sign of front seal leakage on my pump. Your photos especially will help me with this repair project thanks much!