Hello! I have an 87 300d with the 603. I have a noise coming from the engine under load. I thought it was a lifter but not sure. I just did all 6 injector nozzles. If i touch the number 1 & 3 metal injector lines I can feel a thumping / rhythmic knocking. It did this before I changed the injectors too. You can feel it a little in all of the lines but #1 is a little worse & # 3 is extremely pronounced. No noise at idle. Id say the noise starts at around 1500-2000 rpms.

Could this be a lifter or the injection pump? Any help is appreciated. Thanks!

What exactly did you do to the injectors?

Can you provide any more history of the noise? When did it start, or did you buy the car with the noise?

Generally the lifters are noisy at idle, but then quiet down at higher RPM, so I doubt this is a lifter.

It could be a problem with a delivery valve or two on the injection pump, or a deeper problem in the injection pump, or an internal problem (bearings) on the engine.

Can you make a Youtube video of the noise, and post the link?

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

What I just did a month or so ago- replaced injector nozzles & balanced. Replaced delivery valve seals. Cat was also clogged. I’ve had it for almost 10 years & cant remember if it did it when I bought it. It just seemed noisy at the time coming from a bmw. Haven’t driven it much in the last few years. 2nd owner said something happened at 115,000 miles- don’t remember) & it had a new engine put in it from Mercedes - it has a #22 head.

https://youtu.be/1XY3kRqqcEs

You can hear the noise in the beginning. I have it in drive with foot on the brake. It’s not as pronounced without load.

That doesn't sound like injector to me... Typically injector or delivery valve knock is loudest at idle and tapers off above 1500 RPM. The noise it makes is very sharp and metallic, like a hammer striking an anvil.

The noise you recorded comes on with load and has that dull "thud" noise that typically indicates "bottom end" woes. How's your blowby and oil consumption?

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Record yourself reving the engine from the engine bay by pulling on the throttle linkage, I can't tell what it is from the cabin.

__________________
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.

Here’s a better video. The other one was from a few weeks ago.

https://youtu.be/QOnokzR_Q2c

Pretty sure the noise is coming from cylinder 3. The injector feels as though it nailing. I’m not sure how that sounds. Noise was the same before I installed the nozzles.

That sounds like a vacuum pump coming apart to me

You need to rev it up under hood or have someone rev it for you. If you do it, don’t wear loose clothing like a tie.

From 1:35 on I am reving it from under the hood.

The injector lines all should make a "thud" sensation when you touch them. They'll vary with how much space exists between bends and supported areas. The thumping on the line is from the injector pintle opening and seating.

Nailing is very audible. You'll hear it coming from the top end of the engine and it's unmistakable. Your video does not seem to show the noise coming from anywhere around the injectors or the top end, nor does it sound like the typical nailing. The loudness of the noise from underneath the car suggests bottom end. Additionally, nailing typically doesn't occur as RPM's drop after a throttle blip since fuel should not be getting injected at that point.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Eek. That sounds bad. That isn’t a fuel knock. That’s bottom end you can just tell. If it was run low on oil, it could very well be a spun bearing.

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

I can definitely hear the noise above the #3 cylinder. The injector line thuds insanely more on that cylinder than the rest. Its hard to hear or obviously feel that through the video though. You can definitely hear it more under the car.

It doesn't matter how hard that line thuds compared to the rest...the noise you captured is NOT an injector knock.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I realize that as I stated you can hear it under the car. I think the browser did not update & then signed me out. Our responses are mixed up.

Thank you for all your help.