She has always been pretty peppy for a n/a, today I took her out for a wild ride...
REALLY stomped on her, and she was doing good, but now is sluggish. Idling rougher, power is real low, but not fuel starved...
Much more of a dog than before I let it rip-
it was a super hard high speed push.
What's up with this?

btw, just grabbed some diesel purge...

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Think Alternative Energy!
300CD '80 (now gone but not forgotten...)

Jimmy,

You probably overstressed the engine and broke something. Maybe a ring or a valve. Its not a good idea to beat the sh** out an old engine.

Another case of 'If it ain't broke, don't fix it". If something is runnung well, leave well enough alone.You may need more than a WVO conversion now.

P E H

"You probably overstressed the engine and broke something. Maybe a ring or a valve. Its not a good idea to beat the sh** out an old engine."

Haha, that's funny. What I've found is these engines like to be revved out and driven hard.. but that doesn't mean run them at redline or at the rev limiter for minutes at a time.

Maybe you just free'd up some carbon deposits that got lodged somewhere.. keep running it hard!

I am curious to know how you came to this conclusion. I must admit that it is a pretty widely accepted theory, but I just don't get it.

Nearly 200,000 miles in Mercedes Diesel automobiles

It's a fact.. if you baby your diesel it will run horribly.. everything gets all clogged up with soot from lack of flow through the engine. Keep it to the floor and it will run like a German clock.

My idea of an Italian tune-up..........On my way to work, I have to get onto the hiway, so as I'm on the on-ramp, gear selector in third, I will press the pedal more and more as I quickely build speed while looking in the rearview to see how much soot is coming out. When the rpm's are at around 3500 I will lighten up on the pedal then put it in 4th without stressing the tranny. Just before I hit 4th, there is no more soot. I do this every couple of days.

I agree with P.E. that mashing your foot into floor and spinning all that heavy mass up to red-line, is not necessary to blow carbon, in my opinion. I would think that you are running a higher risk doing that than by not running it so high and leaving the small amount of carbon left inside could!

People here say run them hard, drive like you stole it..........Well, I don't disagree with that completely, 3500 rpm is as high as I want to take mine.

Wow, BB, I thought I was conservative when I run the 603 up to 4200 in third with maximum pedal.

When I did a head gasket last year, it was pretty clean in there for 235K!

I've had mine up higher than 3500 a few times but it doesn't seem to do any better than 3500, IMHO Brian....

Yeah, how do you drive one of these without getting over 3500?


Change fuel filters, running hard, pulling lots of fuel, filter clogs, etc, etc..


The great majority of us run out high mile diesels what you'd call hard and have no problem. If doing so broke something, it was weak and needed fixing already. Better now than when your half way into a long trip, yes?

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Something's not right. The 603 can rev over 5K if you push it.

Checked the secondary filter recently??

Tank screen??

Everyone knows that running an engine as hard as possible makes it last longer. That's why race car engines are lucky to last for one race and then have to be rebuilt.

I don't baby my MB engines but I never take them to maximim RPM unless absolutely necessary and they run just fine. ABout the hardest I have run the '80 300SD was near Vail Co going up the mountains at 60 MPH and 4000 RPM outrunning everything else on the road because of the high altitude.

A long hot drive at normal engine speeds with Mobil 1 or Castrol Syntech synthetic oil in the engine is be better for the engine than an "Italian" tune up.


P E H

I have to agree with you, turbodiesel.

Besides, you see the Fins pushing past 6K rpm's driving 10's of thousands of miles on these things with over 400 hp and 3 liters. All stock internals.

Mine sees 5K rpm everyday that I drive it(lest conditions do not permit). It's been that way for 60K miles from 225K. Never ran better.

Then again, we were initially talking about the 617. But you mentioned the 603, but the 603 is a true diesel "screamer".

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

I'd check the basics-how long since your last valve adjustment, condition of the air filter, sudden blowby increase? ever checked for worn timing chain? fuel filters aged? possible bad fuel? I beat mine like a red-headed stepchild-just did a run yesterday to Indianapolis and back for the NCAAs, averaged 80 coming back(they were still passing me like I was standing still), and it ran better afterwards than before-that's about 70 minutes over 3500 RPM!!!

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1982 300DT 190K (Diesel Purge + synthetic oil=smoothness at last!!!)
2004 Ford E-350 6.0 L PSD 227K
2006 Dodge Ram 3500 SRW HO Cummins 4X4 48RE 42K (brute force tow vehicle)
2005 Scion xB wife's rolling pop can
1993 GMC Sierra C3500 6.2 142K

Apples and oranges. These engines are designed to be workhorses.. not only for automobiles but industrial machinery.. they are designed to run at maximum capicity. On the other hand, race car engines are designed to do one thing, and one thing only.. win one race. They are tuned with performance in mind, not engine longevity. The wonderful engineers at Mercedes-Benz designed these engines with longevity in mind.

No no no no no, what I meant was that I don't take it past 3500 rpm! I'm sure it can do red-line, which is I think 5500, I was told here. But why should I push it if i don't think I need to? I believe it's getting de-carboned well enough at 3500. Hey, when I do accellerate fast to 3500, I'm joining cars off the ramp and onto the highway doing 65 or 70 mph very quickly.

At 65 mph, my tach says 2500, that's my normal cruise speed.