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1979 240D 4 spd
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Discussion Starter #1
Hey all - Recently my power steering pump has had a bit of a squeal when the car is on. Not super high pitched, just pretty consistent. It's fairly noticable when idleing. At speed, the engine drowns it out and it cannot be heard. I don't think that it's the belt because when I pour water on it the noise remains the same. The belt tensions are pretty good. I recently adjusted my valves and turned the engine over using the power steering pump bolt. The noise started some weeks after that. Is this something to be worried about? My initial thought is maybe a bearing is shot inside the pump.. However, I know very little about the pumps used in these cars so I'm not sure what to point the finger at. Should I give this immediate attention? It's been around for about a week and a half, and hasn't changed all that much.. I drive ~70 miles a day commuting to and from work.

Thanks all
 

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2001 Volvo V40
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Try replacing the filter and the oil in the steering pump. The filter can be found at the bottom of the reservoir.
 

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1981 240D
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I would have to hear the noise to be certain, but you may have bent your pulley bolt. I know it sounds far fetched, but I did it once with my 300SD. I put way too much directional force on the bolt with my breaker bar. Does it sound like it's pulsating?
 

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1979 240D 4 spd
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Discussion Starter #4
I'd have to listen to it again to make an accurate judgement on the pulsation MerzDiesler. This noise didn't have RIGHT after I did my valves.. there was a few week gap. I took off my cap to check the reservoir. Here's a picture of it... is the PS fluid high enough? Mine doesn't really look like the setup found in the Haynes manual I have, so it's hard to tell.
 

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1981 240D
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I'd have to listen to it again to make an accurate judgement on the pulsation MerzDiesler. This noise didn't have RIGHT after I did my valves.. there was a few week gap. I took off my cap to check the reservoir. Here's a picture of it... is the PS fluid high enough? Mine doesn't really look like the setup found in the Haynes manual I have, so it's hard to tell.
It looks like you are a bit low. I can see the outline of your filter. Also, the ATF is getting a little dark, might be time for a change and filter replacement like Govert said in his post. You can also switch to P/S fluid. Hanes manuals are for general work. Always consult the FSM over a Hanes or Chiltons manual, since these manuals are general guidelines. Hanes and Chiltons use a general template for every vehicle they produce manuals for and they just make a few changes here and there to tailor the manual to a specific vehicle. Mercedes produces manuals for one vehicle: Mercedes. If you decide to change your P/S pump over to P/S fluid, you can remove the return line from the pump, put it in a large jug and with the engine running turn the wheel from lock to lock. After the pump discharges all of the ATF into the jug via the return line, pour a couple bottles of P/S fluid into the reservoir and repeat until you have clear P/S fluid that is not too frothy. When it is all cleaned up, turn off the engine, replace the filter and refill your P/S reservoir. You will have to turn the wheel lock to lock several times to bleed the air out. This is a general technique. It works well for me.
 

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1979 240D 4 spd
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Discussion Starter #6
This is a dumb question.. but what is the FSM? I've seen it all over this site.

The process doesn't sound too bad. How long's that typically take? 45 mins or so?

Any recommendation on P/S fluid? And also, how much is it typically?

Thanks Merz
 

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1981 240D
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P/S fluid is not much more than quality ATF. The whole process should take you no more than an hour or so. It goes faster if you have someone there to help you (turn the steering wheel from lock to lock for you while you pour in the P/S fluid). You should try to have an assistant that has the strength to turn the wheel when the fluid is discharged because the car will not have power steering if there is no fluid. After you have purged the system of all ATF and you have refilled the reservoir with P/S fluid you will have to turn the wheel lock to lock somewhere around 50 times to purge all the air out. Also, just as a note it will not hurt you to keep ATF in the system. There are two schools of thought on this. There are those who feel ATF is detrimental to the system and it should be replaced with P/S fluid and there are those who feel that MB recommended ATF for many years, so why change now? You can search the threads here and see what others say about it. I personally changed mine over to P/S fluid.
 

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1979 240D 4 spd
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Discussion Starter #9
Sounds good - I'm gonna get after this tomorrow. Picking up the filter and the fluid after work. This is doable whilst the vehicle is grounded right? I'm sure it'd be easier with it jacked, but not necessary? I'm gonna change to PS Fluid as well, per your recommendation. I found a good peach parts DIY for this, so I'm gonna follow that. Seems easy enough..

I've had a hard time finding a replacement gasket for the reservoir cap. Not sure how necessary it is to replace?

Govert - Thanks for the link!
 

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1981 240D
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Sounds good - I'm gonna get after this tomorrow. Picking up the filter and the fluid after work. This is doable whilst the vehicle is grounded right? I'm sure it'd be easier with it jacked, but not necessary? I'm gonna change to PS Fluid as well, per your recommendation. I found a good peach parts DIY for this, so I'm gonna follow that. Seems easy enough..

I've had a hard time finding a replacement gasket for the reservoir cap. Not sure how necessary it is to replace?

Govert - Thanks for the link!
Yes, I failed to mention it, but it is much easier on jack stands, but not mandatory. The gasket is very neccessary. It keeps fluid from leaking out and it keeps the cover from rattling loose.
 

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1979 240D 4 spd
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Discussion Starter #11
Merz - I know I need a gasket on the cap, it's just I could only find a replacement gasket online. So, I'm gonna do the filter/fluid replacement asap, but wait until I need other parts online to tag it onto that order. I'm gonna continue to use the gasket that's on my pump right now.

Do you have any advice as far as removing/reinstalling the metal collar/spring from the filter. Is it fairly trivial? That's the only thing I could see being a hastle in this procedure. I appreciate the help.
 

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Merz - I know I need a gasket on the cap, it's just I could only find a replacement gasket online. So, I'm gonna do the filter/fluid replacement asap, but wait until I need other parts online to tag it onto that order. I'm gonna continue to use the gasket that's on my pump right now.

Do you have any advice as far as removing/reinstalling the metal collar/spring from the filter. Is it fairly trivial? That's the only thing I could see being a hastle in this procedure. I appreciate the help.
Unless the original gasket on the cover is completely shot, you should be okay until a replacement arrives. In a pinch you can always go buy a sheet of rubberized-cork gasket paper from your local auto parts store and cut your own, the pump reservoir is not under high pressure or vacuum during operation. The metal collar/spring is fairly easy to remove. The whole principle of operation behind the collar is the spring cocks it to one side so it will not come off. If you push down a little and center the collar on the centering rod, you will be able to pull it off. You may have to wiggle it the whole way, but there is no trick to getting it off. You will see what I mean when you get to it. It's not as hard as it looks. Worst case scenario, you can use a screwdriver to push down on the spring (to take the load off the collar) and the collar will come off. Yours looks fairly new, so it will be pretty snug.
 

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The gearbox has a drain plug near the pitman arm. Use that to drain the ATF or PS fluid. Lift the front end, engine off, and turn wheels side to side (key in ignition position 1). That should get almost all of the old fluid out of the gearbox.

When filling the reservoir, again turn the wheels side to side (drain plug closed, of course) to completely fill the gearbox of the fluid.

Also a good time to replace the low pressure hose if it's bad. High pressure hose is crimped at each end by metal fittings. Low pressure hose is just cut to fit. 1 meter is more than enough for the low pressure hose.
 

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1979 240D 4 spd
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Discussion Starter #15
Beige - I'm a little confused.. the gear box and the P/S reservoir share their fluid? I'm just unsure how the system works (I'm new to working on cars, but hot damn, i love every second of it). I was gonna drain through the return hose on the P/S Pump. Is there one method that is superior to the other?

Also - Yesterday I picked up some NAPA branded P/S fluid to put into my car. I'm changing over from the ATF. Should that fluid be OK for these old Benz's?
 

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Beige - I'm a little confused.. the gear box and the P/S reservoir share their fluid? I'm just unsure how the system works (I'm new to working on cars, but hot damn, i love every second of it). I was gonna drain through the return hose on the P/S Pump. Is there one method that is superior to the other?

Also - Yesterday I picked up some NAPA branded P/S fluid to put into my car. I'm changing over from the ATF. Should that fluid be OK for these old Benz's?
MBeige's way is the correct way to do it and it is how the Mercedes-Benz dealership would do it. The way I told you to do it is a general practice common to non-MB shops and many DIY-ers. It's the way my father taught me to do it. I have used this method to convert every MB I have ever owned and I have never had a problem as a result. The way I told you to do it will not hurt anything so long as you make 100% sure to get all of the old ATF out. Having said that, if you want to do it the way the MB FSM tells you to do it, I would follow MBeige's instructions. MBeige is a very well respected MB guy who has helped me out a ton, so I would never contradict his mechanical advice. If you are new at working on cars, it is a good idea to get into the habit of following the FSM. Mercedes-Benz is the oldest car manufacturer in the world and they know what's best for their cars.

NAPA P/S fluid will be fine as long as it is fresh from a sealed container (like any other fluid, if the container has been open for extended periods it will become contaminated with dust and moisture). Generally speaking with P/S and Brake fluid, the most up-to-date formula will be fine in older cars. With coolant, oil, additives, and ATF I ALWAYS follow MB guidelines, but Brake and P/S fluid are pretty close to universal. Modern manufacturing and refining processes exceed the standards set in the 1970's and 1980's.

And yes, the P/S pump circulates fluid through the steering gear box. It is a hydraulic pump that utilizes hydraulic gear suspension principles to create a "power assist" in turning the worm gears inside the gear box. It is the same principle as quicksand or an air hockey table. In quicksand, the natural flow of water in the depths of the sand make the sand "fluffy" and that's why you sink. Your body movement adds to this effect and that's why people who panic and flail around sink faster. The same with air hockey, the cushion of less dense moving air helps the puck to float. In both examples of the same principle, one joule is multiplied by the physics of hydraulics. This is the least confusing way I can describe this principle (I am an engineer, but I have never been a good teacher).
 

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Beige - I'm a little confused.. the gear box and the P/S reservoir share their fluid? I'm just unsure how the system works (I'm new to working on cars, but hot damn, i love every second of it). I was gonna drain through the return hose on the P/S Pump. Is there one method that is superior to the other?
Steering gearbox, where the steering column meets underchassis steering components. Behind left engine mount.

Draining by the low pressure hose will not get all or most of the old fluid out. The steering gearbox has maybe a quart inside. If you don't drain this, you will have to do the job another time since the fresh fluid will be contaminated.
 

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1979 240D 4 spd
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Discussion Starter #18
So I bought 2 gallons of fluid. If I use the return line method and pump a gallon of P/S fluid through, will that successfully clean the gearbox of old ATF prior to adding fresh P/S fluid? I'm gonna take a peak in my car after work and follow some of the P/S pump lines to locate the steering gearbox.

Side Note: I have a manual transmission - only the automatic transmissions have filters right? My manual one would just have oil?
 

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1981 240D
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So I bought 2 gallons of fluid. If I use the return line method and pump a gallon of P/S fluid through, will that successfully clean the gearbox of old ATF prior to adding fresh P/S fluid? I'm gonna take a peak in my car after work and follow some of the P/S pump lines to locate the steering gearbox.

Side Note: I have a manual transmission - only the automatic transmissions have filters right? My manual one would just have oil?
2 gallons is way more than you will need. Like MBeige said, you should drain the gearbox. I didn't when I did my last conversion and I didn't have any problems, but knowing what I know now, I would consider draining the gearbox. He is right, there will be a certain amount of standing fluid in the gearbox. The drainplug is not too hard to get to.

Your manual transmission will use 30W motor oil. There is no filter.
 

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So I bought 2 gallons of fluid. If I use the return line method and pump a gallon of P/S fluid through, will that successfully clean the gearbox of old ATF prior to adding fresh P/S fluid? I'm gonna take a peak in my car after work and follow some of the P/S pump lines to locate the steering gearbox.

Side Note: I have a manual transmission - only the automatic transmissions have filters right? My manual one would just have oil?
Do not confuse the transmission gearbox with the steering gearbox.

Transmission gearbox is NOT related to steering.

The gearbox you need to drain is behind the left (driver side) engine mount.

1 gallon should suffice. It's just me, but I would opt to use ATF (of the correct specification) recommended in the manual. Others have used P/S fluid in its place with no ill effects.
 
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