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  #1  
Old 10-10-2003, 06:46 PM
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PS fluid/hydraulic fluid

Car in questio is a 98 S500. The car does have auto leveling but does not have ESP.

My poweer steering pump is leaking and the car is going in for service on Monday. In the mean time I wanted to add fluid to hold me over till Monday. However, I am getting conflicking info on whether my car takes regular PS fluid or hydraulic fluid. I suspect that it is hydraulic fluid b/c of the level ride. However, in the technical data section of the owners manual (where it shows the fluid capacities) it shows PS fluid and Hydraulic fluid for ESP. Nowhere, does it specify if PS fluid should be used on all models or models equiped w/o rear auto leveling. Note that the manual is for models 320, 420 and 500, where the 500 is the only model of those three that had rear level ride as standard equipment (I think).

Anyone have the correct answer?


I appreciate everyone's replies!!
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  #2  
Old 10-10-2003, 10:02 PM
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PS fluid/hydraulic fluid

I can tell you that on a 96' 140 body the p/s and hdy fluid are very much different. Sorry!
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  #3  
Old 10-10-2003, 10:15 PM
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I'd guess the reservoirs are separate. The pumps run on a common shaft, with the ESP pump in front of the PS pump if they are like the ones on the W124 TE.

PS fluid will go into the res. on the pump, fluid for the leveling system into the plastic tank on the fender, again if this is like the TE.

Make sure you put the PS fluid in the PS pump reservior, NOT the leveling system.

Peter
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  #4  
Old 10-10-2003, 10:52 PM
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Thanks for your input guys . Anyone else?

I do know that there are two dipsticks that are both below the minimum line. One being the res. located in the front of the engine bay, drivers side above the serpentine belt (pretty sure the PS res.) and the other located to the right of that res., which is labeled hydraulic fluid (self leveling I suppose). Since both res. are low I think they use a common fluid, hydraulic.

Thanks
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  #5  
Old 10-11-2003, 07:55 AM
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Your car has a "tandem" pump configuration. There is a single, belt driven assembly on front of the engine on the driver's side (normally, this is considered the "left" of the engine compartment)
Anyway, there are two pumps in one housing... they DO NOT share the same fluid. The black housing on the top of the assembly is the P/S fluid resevoir. You removed/turned the small black knob on top to read the dipstick for fluid level. The P/S fluid goes only to the P/S pump in the housing, which is located forward (right behind the pulley) on the pump shaft.
The rear section of the housing contains the pump for the leveling system. It uses hydraulic fluid. The resevoir is located on the driver's side under a removeable cover. The resevoir is semi-transparent. It has a small "push in" dispstick located on its top.
Bottom line: No, the fluids are NOT the same. I know folks use various fluids out of personal preference, but I wouldn't risk the seals, etc on anything other than MB approved fluids for these systems.
If it still seems confusing, let us know. I've got one of these "tandem" pumps on the shelf around here somewhere and can post a pix if necessary.
Good luck, KenP
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  #6  
Old 10-11-2003, 11:15 AM
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KenP you are correct!

Before checking the forum this morning I called the dealer and they confirmed that my car takes PS fluid, which is the bitter sweet answer. Yesterday, I went to a MB dealer to purchase hydraulic fluid and 1qt cost me $17.81! So now I have to go buy PS fluid! As I said in a prior post, the hydraulic resevoir was below the minimum line, which I suspect could be the result of another leak or neglect from the previous owner - signifying another problem. Anyone know if this is a common problem?
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  #7  
Old 10-11-2003, 11:42 AM
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Don't usually use hydrualic fluid for the suspension unless either the pump leaks or the accumulators are so bad the struts have been beated to death.

How hard does it ride in the rear? Hydraulic suspension should be very smooth, not bouncy at all. If it is bouncy, the accumulators are gone, need to be replaced.

Shouldn't be a problem at the age of your car.

yes, the hydraulic fluid is expensive. No, don't use anything else, you may never have to add the whole bottle.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 10-11-2003, 09:07 PM
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If it is bouncy, the accumulators are gone

There IS a reason the hdy fluid is low on the rear. The only place for it to go is through the accumator seals or the tank that holds the fluid. My guess is the accumators. Even so, there will be NO fluid on the ground as it leaks throught the seal into another part of the accumators. If and when you replace them, replace both. They run 150 or so each plus 150 to install them. If the car is bouncy in the rear they are bad. If to seems to not take a corner turning one way than the other, you have one bad one. Remember to always replace both as the hdy fluid circulates through both and back to the res as that is where the pump is.
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  #9  
Old 10-12-2003, 10:01 AM
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I only had the car two months, so I really don't have much to compare the ride to. My last car was a 2000 Acura RL, which road nice, but did not have the composure that the S has. The car definitely has a slightly bouncy ride, but not excessive like a town car. The one thing I do hear from the suspension is a thumping noise from the rear. The noise is only heard when city driving (under 30 mph). My guess is that the noise is either bad rear strut mounts or worse yet rear struts!

Thanks for everyone's replies!!!
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  #10  
Old 10-12-2003, 11:04 AM
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The accumulators are gone!

The accumulators are gone! If it has even the slightest bounce, they are history. What the thumping noise is that the person b-4 you failed to replace the bad accumulators and the bouncing has caused the rear hdy shock mounts to go bad. $140-150 ea on the accumulators, $90-100 each on the shock mounts, $140 to 200 labor at a non MB dealer.

Good Luck!
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  #11  
Old 10-12-2003, 11:46 AM
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Thanks for the info!!

Hopefully, your are correct about the accumulators and mounts. It makes sense in my mind. I just hope that the struts are fine. It's bad enough that they are about $570 each w/o labor, but with just 65k miles on the car you would think they would have a longer life cycle.

Hopefully the accumulators are covered under my warranty!
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  #12  
Old 10-12-2003, 01:17 PM
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If the rear doesn't sag, the struts are fine -- all the oil leaks out and then they can't hold the car up.

Accumulators seem to have a life of 6-8 years or 100,000 miles or so -- the nitrogen "leaks" through the diaphram and goes out the pump, there isn't any way I know of to prevent this. Any material flexible enough to use as a diaphram cannot be make completely non-permiable to nitrogen. Rupture of the diaphrams is rather rare, I believe.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 10-12-2003, 02:20 PM
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Last ones I replaced in 35K!

Last ones I replaced in 35K! Who knows how long they might last???
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