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  #1  
Old 06-07-2017, 10:06 PM
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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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2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k
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  #2  
Old 06-07-2017, 10:14 PM
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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.
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  #3  
Old 06-07-2017, 10:21 PM
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Quote:
Originally Posted by Father Of Giants View Post
Could be crappy fuel tbh.
You can try going to a high cetane diesel station.

I'm in the same boat as you, rebuilt my injectors as well.


You can also try installing new springs, o-rings, and copper washers inside the delivery valves of the injection pump.
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
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  #4  
Old 06-08-2017, 01:39 AM
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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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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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  #5  
Old 06-08-2017, 10:40 AM
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Quote:
Originally Posted by jake12tech View Post
Delivery valves have been replaced on both.
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.
__________________
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.
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  #6  
Old 06-08-2017, 11:37 AM
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Quote:
Originally Posted by RunningTooHot View Post
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.
I have a similar low-RPM knock as Jake does, though not as loud. It has recently started up and goes away above 850-900 RPM and comes in ~700 RPM. Like the one discussed here, it's pretty well quiet at idle. I've isolated it to Cylinder #5, which is one I haven't done anything with yet. I suspect another delivery valve based on my history with this car. It does give a good chance to try the valve-lapping idea to see if it stops the noise in that cylinder. #1 and #2 that have the lapped valves are still quiet. To keep from hijacking this thread, I'll keep my progress on that topic in the other thread.
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  #7  
Old 06-08-2017, 03:32 PM
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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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  #8  
Old 06-08-2017, 04:08 PM
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Quote:
Originally Posted by Diesel911 View Post
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.
After redoing the entire injection system, I need to move on to these two. I'll defeat the knock, one day...
__________________
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.
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  #9  
Old 06-08-2017, 04:25 PM
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Quote:
Originally Posted by Diseasel300 View Post
I have a similar low-RPM knock as Jake does, though not as loud. It has recently started up and goes away above 850-900 RPM and comes in ~700 RPM. Like the one discussed here, it's pretty well quiet at idle. I've isolated it to Cylinder #5, which is one I haven't done anything with yet. I suspect another delivery valve based on my history with this car. It does give a good chance to try the valve-lapping idea to see if it stops the noise in that cylinder. #1 and #2 that have the lapped valves are still quiet. To keep from hijacking this thread, I'll keep my progress on that topic in the other thread.
Quote:
Originally Posted by RunningTooHot View Post
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.
I meant to say the crusher washers... Not the valves themselves! It's the #4 cyl on #1 99 and #5 on #2 99 e300.


Quote:
Originally Posted by Diesel911 View Post
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.
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.
__________________
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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  #10  
Old 06-08-2017, 09:11 PM
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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.
__________________
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.
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  #11  
Old 06-08-2017, 09:29 PM
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A compression check may turn up a weak cylinder.
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  #12  
Old 06-08-2017, 10:11 PM
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Quote:
Originally Posted by RunningTooHot View Post
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.
this forum is great, always a great wealth of knowledge on here and someone always willing to help. i see you have almost as many miles on your 95 om606 as my 99 turbo.. that's awesome to see. the way it looks my motor can run a few hundred more thousand miles

Quote:
Originally Posted by Mxfrank View Post
A compression check may turn up a weak cylinder.
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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