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Nagging Combustion Knock
Both of my '99 E300s have a combustion knock that I'm curious if anyone else seems to have and solved it. Idle is perfect, no knock quiet combustion. Above 700rpms I'm getting a nailing. Delivery valves have been replaced on both, injectors were rebuilt on my cars as well. No fuel leaks at all & crush washers replaced on injectors after removal.
Both cars it goes away on diesel purge, I'm assuming because of the high levels of cetane in purge is masking whatever it is momentarily. Here's what I'm talking about.. It's strange cause my '98 e300 doesn't do it. https://www.youtube.com/watch?v=7sLfQ9wZLuE After revving it, isn't as responsive coming down in idle and seems to hesitate a little.
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Only diesels in this driveway. 2005 E320 CDI 243k Black/Black 2008 Chevy 3500HD Duramax 340k 2004 Chevy 2500HD Duramax 220k |
#2
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You can try going to a high cetane diesel station.
I'm in the same boat as you. I've done exactly as you have and no dice.
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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily 1992 Mercedes 300D 2.5 202,000 - Pure junk 2000 Mercedes E320 Black - 136,000 miles - Needs repair Don't forget to grease the screw and threads on the spring compressor. |
#3
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Did that whole deal with the pump, no avail on them. Both cars had them done. I throw cetane booster in each fillup. I think you just may never get a perfect IDI. It hasn't affected my fuel economy, so I guess I shouldn't go looking for problems. All 3 cars routinely return 24mpg city 33mpg highway. 36 if I drive at 65mph which never happens.
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Only diesels in this driveway. 2005 E320 CDI 243k Black/Black 2008 Chevy 3500HD Duramax 340k 2004 Chevy 2500HD Duramax 220k |
#4
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On tick-over I can hear a tappety noise before it's revved, this is exactly the same as mine but possibly slightly louder due to tinny exhaust.
The history behind my situation is slightly more complicated (see thread) but hoping water injection may help with any carbon build up.
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David 1996 Mercedes S124 E300TD - 129k - rolling restoration project - 1998 Mercedes W210 300TD - 118k (assimilated into above vehicle) |
#5
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Question:
Just confirming - you are saying you replaced all the delivery valves - not just the crush washers? If so, were the replacement DV's new ones or used ones? It sure sounds like it's originating from one cylinder, and I'll bet you've already tried to isolate which one. I can also see you're already aware of this thread, where Diseasel300 found the smoking gun and fixed his problem (toward the end of the thread): Delivery valve internal leak as a cause of nailing? Yes? No? Maybe??? BTW, I'm in the same boat as you. I had Greaser rebuild the injectors, and then I replaced the DV seals a while ago. Same problem still exists. It sounds scary loud when in that narrow RPM band. I try to "drive around it" as best I can, since it only occurs at light loads. (But that's an asinine approach, as I'd like to FIX it!) Also, when I'm in areas that sell Diesel HPR (which has an astronomical cetane rating) my cars love that stuff. They run much quieter, and while it will mitigate that horrid low-rpm knock, it doesn't completely eliminate it. Even if it did, that's still only a band-aid approach. I'd like to know how to solve the actual problem.
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Current rolling stock: 2001 E55 183,000+ Newest member of the fleet. 2002 E320 83,000 - The "cream-puff"! 1992 500E 217,000+ 1995 E300D 412,000+ 1998 E300D 155,000+ 2001 E320 227,000+ 2001 E320 Wagon, 177,000+ Prior MBZ’s: 1952 220 Cab A 1966 300SE 1971 280SE 1973 350SLC (euro) 1980 450SLC 1980 450SLC (#2) 1978 450SLC 5.0 1984 300D ~243,000 & fondly remembered 1993 500E - sorely missed. 1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years. |
#6
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Quote:
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#7
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I did not read each post closely. How about Fuel Injection Pump Timing, Camshaft Timing (changed due to Timing Chain Stretch and or Timing Gear Wear) and then there is the ERG/emissions system.
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84 300D, 82 Volvo 244Gl Diesel |
#8
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After redoing the entire injection system, I need to move on to these two. I'll defeat the knock, one day...
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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily 1992 Mercedes 300D 2.5 202,000 - Pure junk 2000 Mercedes E320 Black - 136,000 miles - Needs repair Don't forget to grease the screw and threads on the spring compressor. |
#9
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Quote:
Quote:
I doubt timing is an issue, too low of mileage for a maintained double row and never missed an oil change. 5k synthetic oil every single time with a filter. EGR may be a possibility. I do have blowby at the EGR valve and its spitting out oily residue. the high mileage e300 has a new chain with adjusted timing and the chain has only 40k miles on it.
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Only diesels in this driveway. 2005 E320 CDI 243k Black/Black 2008 Chevy 3500HD Duramax 340k 2004 Chevy 2500HD Duramax 220k |
#10
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Looks like a good idea to keep an eye on that other thread. I think Diseasel300 may have found the solution for us.
You just gotta love the collaborative effort & knowledge sharing of a good internet community like this! - It almost restores my faith in humanity.
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Current rolling stock: 2001 E55 183,000+ Newest member of the fleet. 2002 E320 83,000 - The "cream-puff"! 1992 500E 217,000+ 1995 E300D 412,000+ 1998 E300D 155,000+ 2001 E320 227,000+ 2001 E320 Wagon, 177,000+ Prior MBZ’s: 1952 220 Cab A 1966 300SE 1971 280SE 1973 350SLC (euro) 1980 450SLC 1980 450SLC (#2) 1978 450SLC 5.0 1984 300D ~243,000 & fondly remembered 1993 500E - sorely missed. 1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years. |
#11
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A compression check may turn up a weak cylinder.
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#12
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Quote:
I'd have to agree on the higher mileage E300, but I ran a compression check on it when I got it out of curiosity and the cylinders are equal and compression is pretty close to spec.. it just had a valve job as well not too long ago within the past 50k miles. i think it may be the pump after reading the DV thread by diseasel. i think i'm gonna try and lap the valves themselves and see what happens on my spare 606 pump and run it on the car and see if it shuts it up
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Only diesels in this driveway. 2005 E320 CDI 243k Black/Black 2008 Chevy 3500HD Duramax 340k 2004 Chevy 2500HD Duramax 220k |
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