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  #1  
Old 04-25-2008, 12:43 PM
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Location: Portland, Oregon
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W126 questions: RPM, temp, etc

Hi folks ~

I just replaced my demised 300TD with an '87 300SDL. So far I love it, but I have a couple questions, mostly where it's different from the W123:
  • Temperature: It seems to warm up much faster, but even after 30 minutes on the freeway doesn't get much over 80 degrees. The W123 usually ran at about 100 degrees. That's with and without the A/C, but we've not yet had a day over 60 degrees here. Is this normal?
  • RPM: The W123 seemed happiest at about 3100RPM. What's optimum range for this engine?
  • Speedo dots: I feel silly asking this; I've been assuming that the little dots on the speedometer represent optimum cruising speed. Or is it maximum speed for a particular gear? Or something else?
  • Turbo: The wagon's turbo was really obvious. At about 2k RPM it would start to whine, that would increase in pitch until about 2.2k or 2.3k, then the whine would stop and the boost would kick in noticeably. With the SDL I get very little indication (except that it's much faster than the wagon ). Was the wagon out-of-normal? Is this normal for the W126?
  • Flooring it: The advice I'd read about the W123 was, "Baby it until it reaches operating temperature, then drive it like you stole it -- assuming valves, time chain, etc are in good order." Save advice for the W126?

Thanks!
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2003 E320 wagon, ~80k, "Sputnik"
1987 300 SDL, ~160k, "The Pimp Daddy" (sold April 2010)
1984 300 TD, ~200k, "Das Boot" (Demised March 2008)
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  #2  
Old 04-25-2008, 01:56 PM
Hatterasguy's Avatar
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The needle should just about cut the 8 in half on the temp guage. Since this is a real guage the needle will move if you really make the engine work, but thats where it should run under normal use.

SDL's seem to like to run 70-80, I usualy keep the RPM's at 3k, but they are perfectly happy going faster.

You shouldn't hear the turbo, if you do something is leaking. If its adjusted properly you shouldn't feel the boost kick in either. However on most of them they are dogs to around 2,500 than you can feel the turbo start to work. Do a search on the ALDA and you can adjust that right out.

A diesel is a diesel, they like to be run hard. Just don't thrash the engine when its cold and if you come off boost give the turbo a minute to slow down before shutting it off. However the 603 is pretty powerfull so if you floor it all the time you will probably get a ticket and burn a lot of fuel. I usualy let mine shift somewhere between 2k-2.5k; when their is no traffic I keep it below 2k.
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  #3  
Old 04-25-2008, 09:45 PM
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Quote:
Originally Posted by Hatterasguy View Post
The needle should just about cut the 8 in half on the temp guage. Since this is a real guage the needle will move if you really make the engine work, but thats where it should run under normal use.

SDL's seem to like to run 70-80, I usualy keep the RPM's at 3k, but they are perfectly happy going faster.

You shouldn't hear the turbo, if you do something is leaking. If its adjusted properly you shouldn't feel the boost kick in either. However on most of them they are dogs to around 2,500 than you can feel the turbo start to work. Do a search on the ALDA and you can adjust that right out.

A diesel is a diesel, they like to be run hard. Just don't thrash the engine when its cold and if you come off boost give the turbo a minute to slow down before shutting it off. However the 603 is pretty powerfull so if you floor it all the time you will probably get a ticket and burn a lot of fuel. I usualy let mine shift somewhere between 2k-2.5k; when their is no traffic I keep it below 2k.
DITTO all of what he said!!! My current 300SDL is NOT a dog until 2500 RPM.
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Old 04-25-2008, 09:49 PM
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The speedometer dots are the maximum speed at which it is safe to shift DOWN into a gear. The transmission doesn't have the ability to prevent shifts into gears that are too low for the road speed like modern transmissions, or at least not to as foolproof an extent, so the dots indicate not to shift down into the gear indicated by them if your speed is in excess.

2 dots = don't shift into 2 if you're going faster than this.

If the needle goes past the dots while accelerating rather than decelerating, you're okay. Mine, however, physically won't do this.
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  #5  
Old 04-26-2008, 12:13 PM
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Quote:
Originally Posted by bustedbenz View Post
The speedometer dots are the maximum speed at which it is safe to shift DOWN into a gear.
Ooh, that's nice to know. I try never to force-shift the car down anyway. Now I have to pay even less attention to those marks Thanks!
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1984 300 TD, ~200k, "Das Boot" (Demised March 2008)
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  #6  
Old 04-26-2008, 02:40 PM
Hatterasguy's Avatar
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Location: Milford, CT
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Yeah these are cars built for people who know how to drive, before all the modern legal BS. No shifter lock, and you will break something if you knock it into 2nd at 70.

Thats why I like them.
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  #7  
Old 04-27-2008, 02:11 AM
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Quote:
Originally Posted by Randall Hansen View Post
Hi folks ~

I just replaced my demised 300TD with an '87 300SDL. So far I love it, but I have a couple questions, mostly where it's different from the W123:
  • Temperature: It seems to warm up much faster, but even after 30 minutes on the freeway doesn't get much over 80 degrees. The W123 usually ran at about 100 degrees. That's with and without the A/C, but we've not yet had a day over 60 degrees here. Is this normal?
  • RPM: The W123 seemed happiest at about 3100RPM. What's optimum range for this engine?
  • Speedo dots: I feel silly asking this; I've been assuming that the little dots on the speedometer represent optimum cruising speed. Or is it maximum speed for a particular gear? Or something else?
  • Turbo: The wagon's turbo was really obvious. At about 2k RPM it would start to whine, that would increase in pitch until about 2.2k or 2.3k, then the whine would stop and the boost would kick in noticeably. With the SDL I get very little indication (except that it's much faster than the wagon ). Was the wagon out-of-normal? Is this normal for the W126?
  • Flooring it: The advice I'd read about the W123 was, "Baby it until it reaches operating temperature, then drive it like you stole it -- assuming valves, time chain, etc are in good order." Save advice for the W126?

Thanks!


W126 also have a larger cooling system than the 123s.

I've dorked along from 60mph on a trip to 80mph. Econ is better the slower you go (obviously).

SDL also have some emission crap to reduce turbo sound. Plus the KKK doesn't make too much noise.

Max the ALDA out for better off the light performance too.
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