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S-Class (W140) 1991-1999: 300 SD, S 350TD, 300 SE 2.8, S280, 300 SE 3.2, 300 SEL 3.2, S320, S320L, 400 SE, S420, 400 SEL, S420L, 500 SE, S500, 500 SEL, S500L, 600 SE, S600, 600 SEL, S600L, 500 SEC, 600 SEC

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Old 03-15-2008, 12:16 AM   #1
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Join Date: Mar 2008
Posts: 30
Drives: 94 mercedes s320
s320 with rpm going up and down + transmission problem

guys i need ur help . just bought this car with some problems 94 s320

i changed air filter, oil, plugs
-when i start the car it works fine but after couple minutes rpm start going up & down, antifreeze leaks from over the oil pan could that be the reason

- transmission works fine in the city. but rpm goes quite high after 100kms seems like last gear doesnt change. is there a switch for overdrive or its a problem with the transmission?

-there are two switches one is beside shifter (one side is pictured man and otherside is dot) and second switch is pictured like tire on the front dashboard --->what are the functions of these. is there an online owner's manual for w140?

i would really appreciate ur help
thanks
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Old 03-17-2008, 10:01 AM   #2
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Join Date: Apr 2004
Location: Mesa, AZ
Posts: 373
Drives: 1996 S320 & 2006 E320 CDI & 2006 Dodge 2500 Diesel Pick up
Quote:
Originally Posted by my_galaxy View Post
guys i need ur help . just bought this car with some problems 94 s320

i changed air filter, oil, plugs
-when i start the car it works fine but after couple minutes rpm start going up & down, antifreeze leaks from over the oil pan could that be the reason

- transmission works fine in the city. but rpm goes quite high after 100kms seems like last gear doesnt change. is there a switch for overdrive or its a problem with the transmission?

-there are two switches one is beside shifter (one side is pictured man and otherside is dot) and second switch is pictured like tire on the front dashboard --->what are the functions of these. is there an online owner's manual for w140?

i would really appreciate ur help
thanks
I had the same issue with the RPM going "up & down". It was a fuel pressure regulator problem that was a quick easy fix. The high rev at freeway speed could be you put the shifter in the performance position. With the shifter in drive you will see it can be pushed to the left. You can feel it click into place, thatís the performance mode. So try just pulling it down just into the normal position and see if that helps
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Old 03-20-2008, 09:35 AM   #3
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Join Date: Mar 2008
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Drives: 94 mercedes s320
thanks rod sphon
just wondering, did you consult with mb dealershipas well?. they are saying it has something to do with air. air is leaking from somewhere. was ur s320 was going up and down all the time or once in a while?
thanks
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Old 03-21-2008, 09:37 AM   #4
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Join Date: Apr 2004
Location: Mesa, AZ
Posts: 373
Drives: 1996 S320 & 2006 E320 CDI & 2006 Dodge 2500 Diesel Pick up
I didn't consult the dealer I tend to stay away from them. Find a good indy shop in your area & you'll save a bundle over a dealer. I do 95% of my oun repairs on the car but have an indy I have used and I will ask questions and then do work myself.
They are correct it could be an air leak, or at least a vaccum leak. You can do a back yard test for that by sprayig carb cleaner slowly at joints & conections of you vaccum lines. In a lot of cases if you are loosing vaccum it will suck the cleaner in and that will cause an rpm increase(like adding more gas). If you find a leak fix the air line. Remember these hard plastic air lines get brittle as they get old do to the heat under the hood. They can & will crack any place if they are touched. So check for cracks or breaks.
To check your fuel reg. just pull the Vaccum line off of it and smell for gas in the end of the line. The diaphram in the reg goes out allowing a small amout of gas into the vac line. If you smell gas my guess is its bad. As I recall the regulator was about $100 and easy to change. Hope that helps somehow.

What if anything did you figure out with the transmission?
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Old 03-21-2008, 06:43 PM   #5
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Join Date: Mar 2008
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Drives: 94 mercedes s320
hi rod
thanks for your help. when i shift it to d it goes right into 4. it seems like the spring inside is shot from left side i am going to rip it apart tommorow and so and i will let you know. when car is cold and i drive, transmission change gears and little hight rpm is it normal? that luca s transmission lubrication is it any help?
i did put two fuel injector cleaners in half tank and luca s fuel injector in next tank and ran it off on highway with around 3500 rpm and now rpm doesnt go up and down much. i just bought telescope to hear any leakage. i never thought off ur way (thanks)

i would update once i find out around transmission
thanks
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Old 03-22-2008, 01:58 AM   #6
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Join Date: Apr 2004
Location: Mesa, AZ
Posts: 373
Drives: 1996 S320 & 2006 E320 CDI & 2006 Dodge 2500 Diesel Pick up
"when car is cold and i drive, transmission change gears and little hight rpm is it normal? that luca s transmission lubrication is it any help?"

To answer this question - the answer is yes, the transmission stays in a warmup mode for a short while until it warms up. This is to save your transmission. Don't push it. It only stays that was for a few minutes or a couple block. Usually by the time I get to the main road (maybe 1/4 mile) its warm and shifting the way you would expect.
I hope whatever it out of wack at the shifter is easy to fix.
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Old 03-22-2008, 10:31 AM   #7
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Drives: 94 mercedes s320
yea thanks to all you helpful guys, this forum is swell
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Old 03-22-2008, 10:31 AM
 
 
 
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1996, car, class, mercedes, overdrive, pressure, problem, rpms, s320, starting, test, transmission, transmissiono, w140, working



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