I was coming back from GA yesterday and just south of Richmond VA the I noticed I couldn't cut the cruise off with the switch, and the car wanted to accelerate on its own. I was going 80. I used the brakes to slow down enough to exit(while under power), and the car kept on wanting to accelerate in 4th as I came to a stop and killed the engine. Thinking it was just an electrical glitch with the cruise actuator, I started it back up and it revved to 5k in neutral under no load. Killed engine immediately, then tried again and it did it again and I killed it immediately, but not before it revved to 5k. I crapped in my pants twice. Turns out the two bolts holding the front accelerator linkage plate to the valve cover vibrated loose enabling that part of the linkage to get loose and bind and hold wide open. I had just done a valve adjustment, and merely snugged those bolts. You can bet I torqued them down hard after seeing that. I didn't torque them down hard to begin with because I'm always worried about overtorquing things, especially when it comes to steel bolts in aluminum threads.
My question is thus:
1) how much damage have I done to my car

Car runs fine with no suspect knocking noises, shifts fine- but there is a psychological element that makes me think I hear little subtleties that I haven't heard before. My mind will mess with me like that at times like this. I understand that revving under no load while cold is very bad, but while at operating temp??? The car has been accidentally revved like that 3 times now while in my ownership. Had to lean on the brakes to slow down- but didn't smell anything burning when I got the car stopped. All systems seem nominal. I'm worried a rod bearing or something like that has had its life drastically shortened by this incident, or my transmission has been damaged. Anybody???
Hopefully you can put my mind at ease
Got home from vacation last night to find my kitchen full of the upstairs neighbors wastewater
My goodness what a week I'm having

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Since the engine was fully warm and had oil pressure, the chances of damage are much less than if this had happened on a stone cold start up. At least you shut the car off within seconds. If you have ever seen how many "mechanics" abuse customers cars, you wouldn't be worried. When I had the brakes replaced on the Eldorado, the mechanic pulled around to the side of the shop and did a full burn out with the car. What a moron.

I think your car is fine. It is not like you are revving to 5K under no load every day. I think a few isolated incidences like this one should cause no undue wear on the motor, especially if it is well maintained. Unfortunately the only way to check a rod bearing is to pull the engine apart. Maybe an oil analysis will tell you if you have a more than acceptable amount of bearing material in the oil.

I hope the wastewater came from the neighbor's kitchen and not their bathroom.

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Doug

1987 300TD x 3
2005 E320CDI

One of the older guys in my last shop told me one how when these engines came out, they had one on a stand at school, and let it run wide open all day long purposely. no damage. of course, that was when it was new, but I don't suspect you hurt anything with what you did.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Good point, I hope the same thing.

I would agree, this is probably much worse than what happened with your engine. I would bet it's OK.

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Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Probably the best Italian Tune Up it ever had!

I agree probably no damage at all.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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No harm at all except your dirty underwear I believe. Mercedes engines are basically built to rev pretty good. Five thousand is is not enought to disenigrate them really when previously warmed up. Also remember in your instance you were probably still only up against the injection pump govenor. The loss of the injection pump itself is more likely at higher reves. That is the primary reason for the rpm limiter or govenor in these designs rather than the engine itself I believe. Now when you are running away on base oil for instance there is no govenor protection at all. I have no ideal how high the engine can scream as the only fuel limitation then is what it can get. A small amount of medium locktight might be a good ideal on bolts you do not want to torque down too much..

65ft down there was a blockage in the drain, probably caused by the aforementioned upstairs neighbor and her tendency to want to pour her dinner down her kitchen sink. I'll need some new base cabinets, the drawers were all full of gray water with what looked like couscous in it. All contents ruined. Imagine driving 12 hours, having the ***** scared out of you on the way, thinking you were going to get a nice hot shower WRONG there's a polluted lake in your kitchen
things are tough all over I guess

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Happend to me with the SD when I was trying to start it last winter. I bit to much throttle and starting fluid, when she cought she ran to almost 5k before I killed it. That was with below zero oil. Never noticed a difference either way.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Wash the underwear in bleach, clean the seat and dont give it another thought.

You definately did nothing to your car.


Just be glad you did not get into an accident.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

I doubt you did any damage. Worst case, it will live to 995K miles insted of 1 million.

im surprised how high these engines rev... ive never seen a diesel rev to 4500... mine gets up to 4k when i have to merge into traffic.. i dont like doing it but its either that or be creamed by a peterbuilt

For the longest time I was afraid to punch mine to the floor for fear of blowing it up. I wasn't used to such a high revving diesel engine.

Now that I'm used to it I've come close to over revving my F250 PS diesel pickup.

These cars also warm up faster than any diesel I've ever driven.

Cheers,

Bill

yea they do. the guague is on 80C before i leave my subdivision most of the time.. i cant wait for the winter here in fl

I've never had any fear of revving my 300D hard - I just don't rev it as high as the one's I'd valet park back at the country club when I was 16...

bnc