Occasionally , It's GOOD For Them
 

Most of you guys have turbos and newer Merc's .

When 1st. I bought my 1978 NA 300CD it was _really_ loaded up from chugging 'round West L.A. so after the usual tune , valve adjust , oil & filter etc. , I hopped onto the freeway @ 03:30 or so and held the pedal to the metal from South Central L.A. all the way up & over the hill into North Hollywood .

After cresting the hill it belched out a large black cloud of soot & crap , nailed quite loudly then acellerated up to 95 or so , the front end was a bit loose so I didn't push it beyond that .

Anyone who has an older Diesel should do this at least once a year to de-coke it , makes for a nice smooth idle and more power & economy too .

I agree , traveling at warp speeds all the time in elderly Mercedes Diesels is gambling with your engine but the " Italian Tune-Up " is a good thing .

Nate

I hit 110 coming back from delivering a hood, tranny, RR door, and something else to the NY area. I DID NOT DRIVE 110 with a W126 hood on the roof of my car, it was on the way back. She did go through a bit of motor oil on that trip - at those speeds, and if I can recollect correctly, the fuel filter unspun itself and I was stopped at the other end of PA looking for the Gosh Darned fuel filter rubber O-Ring.

98 with the daily
65 with the 84.....hey.....it's not broke in yet:D

The SDL sees 100 on a fairly regular bassis, and its engine is run to 5k rpm all the time.

You cannot hurt a good MB by driving it fast, or running it threw its rev range. Thats what they are built for, if your oil is good, and your engine is in tune you can't hurt it.

I have never, ever heard of a Mercedes engine in good condition blowing up at redline. I have heard of many Japanese cars doing this...:D

105
 

85 TDT daily driver since 1986
Top speed 105 (downhill), I have found 90-95 to be a good cruising speed when conditions allow (Ohio turnpike late at night, route 200 in Montana anytime).

I agree with what has been said, a LONG drive at high speed seems to only make the engine sound nicer.

Steve

Cruising I top out at around 60mph any faster just does not sound right (then again I am not sure what it should sound like) I had it upto 70 +/- 2mph once chasing a cab who cut me off badly as in would have hit me if I did not slam on the breaks and turn to the right into a curb (had to get close enough so my 10x zoom could see his license plate :-) I hate how the engine screams I am always fearful I am going to break it so until I know what it should sound like I keep it around 60mph tops :-)

Chris Taylor
http://www.nerys.com/

What Are You Driving ?
 

I assume you have either a 240D or those silly low profile tires ? .

SWMBO's '81 240D likes 60 ~ 65 mph empty or fully loaded , they're designed as City cars or Taxis so the final drive is kinda low .

I've had her 240D over 80 and it was humming along but I don't like to run it against the governor , it used lots of fuel and some oil when I drive it over 65 MPH .

-Nate

I have a 76 300D w115

Low Top Speed
 

So , it has an OM67 N/A engine then ? .

Must have some really short gears in it or is it the older three speed slushbox tranny ? .

I'm piqued ! I've not yet seen a 5 cylinder W-115 Diesel in person .

No idea what engine it has I just know its an inline 5c I will take a picture today. it is 4speed and it will go 70 but the engine sounds like its screaming (to me at least) and I am afraid to push it that fast. For all I know this is normal but I do know that none of my gas cars race like that at 70mph (well except my 74 Thing which I do not think can do 70 even with a rocket motor assist :-) or maybe its just that I do not hear it ?? I have NO familiarity diesels so I have no idea what is and is not normal so I err on the side of assuming anything I do not like is not good and avoid making it happen :-) better than the alternative of assuming its normal and blowing something up :-)

Chris Taylor
http://www.nerys.com/

Fastest I have gone...maybe 80 or so. The 3.69 rear I have in the car kind of limits my top speed.

@ Nerys
I drive a W115 300D and I have gotten it to 90 (according to the cop who pulled me over I was only going 85 :o ) and it sounded really good and relatively smooth. I think you might have a transmission problem, like maybe you are stuck in third gear perhaps?

Nope tranny seems fine. shifts good strong smooth and ontime. also I can clearly hear and feel all 4 shift points and all 4 gears.

Maybe tommorrow I will "see how fast" it can go. I have never tried before because I did not like the sound. I was not sure if making the engine "go that fast" was safe or not. Alas I have no way to measure RPM. is there a way I can measure the RPM of the engine ? something I can rig up under the hook and stick a gauge in front of the window so I can see what the RPM is ?

Chris Taylor
http://www.nerys.com/

If you're engine is confirmed to be in good shape: Wear earplugs and keep your right foot pasted. You will not hurt it, no matter how hard you try.

Driving WFO
 

Chris ;

You should drive it pedal to the metal occasionally but in general drive it to where it's happy sounding for maximum fuel economy & engine life .

Diesel engines have governors built into the IP so over speeding it is very difficult .

It's a 4 speed automatic then ? sweet .

The noise does not bother me these engines are not nearly as loud as people complain and I have good ears. I was just fearful that it was "bad" for the engine to do that :-)

I will try it tommorrow and see what happens. ie see how fast it will go if I just hold the pedal down.

I am not sure if the engine is good though I believe it is. it runs very well never gives me any problems starting (except the coughs on cold days but it never stalls and always starts I just have to keep the pedal down till its done having a fit (about 5-8 seconds) once it RPM's up and is smooth I can let off the gas and it will high idle just fine (idle knob turned up) in warmer weather I do not have to do this at all.

ONE time "smoke" came from under the hood. I have never tracked down what that was. I was in a parking lot. I turned on the key to warm the plugs to start it and then decided I did not need to start it so I turned it off and then turned to key to on position so I could get power from the cigarette outlet (gonna have to rewire that) a few minutes later SMOKE came from under the hood. I almost panicked what the hell do I do so I just started the engine (I know once it was running I would very likely get home if nothing was on fire and it did not stall) got out and looked but nothing ??? it never did it again and I never figured out what it was but either way I assumed it had something to do with the way I handled the "start" process so from now on I never turn the key unless I intend to start it just in case!! and if I do turn it and do not need to start it I go through with a full start and then turn it off. Just in case :-) I have never been willing to "test" this for fear of breaking something expensive. not so much in parts but in GAS I drive so many miles that if I say burned a plug the COST to me in gas to drive my van till I get a new set of plugs would result in me buying more dollars in gas than the plugs would cost :-) so I do not want to break it needlessly :-)

Now that I have read more on this I am still not sure what happened but figure it must have been the glow plugs. maybe they got extra hot from the first full warm up and then the second time within seconds of turning the key again (ie maybe doing that defeated the 110sec timer and they heated for longer than that 110sec again ??) and just started to toast some of the grease of something?? no idea really.

We shall see how fast this critter will go tomorrow. there is a nice stretch of 95 close to me if I keep it short I don't really have to worry about being caught seeing as the status quo on this stretch feels more like 90mph ie when I am doing 65-70 in my van people are still whizzing by me.

I would like to be able to go faster ie 65ish only because sometimes I drive on 65mph speed limit roads and some of them are downright DANGEROUS if your going too slow :-) If the racing sound of the engine is normal and not harmful I can live with it but again because of my ZERO past experience with these I had no way to know WHAT is and is not normal/good :-)

I have a steady and slow attitude to driving. I get more time to react to dangers and I may get to the destinations 30 seconds to 2 minutes slower than you but I might save a gallon of gas in the process. Might not seem like much but over the period of a year that could be hundreds of dollars :-)

Over a lifetime that could be several new cars :-)

Chris Taylor
http://www.nerys.com/

i think the fastest i have gone in my 240D is 75... and that was downhill with a strong tailwind :eek: