I have a W201 2.5 Diesel non-turbo (602.911) (euro version) from 1986
It has done about 144.000 KM (90.000 miles?)

When the engine is cold, it doesn't nail, only when its warm 80 degree(176 f)

stationair w201 diesel - YouTube

Nailing start around 1300 rpm to 1800 rpm.
Around 1500 rpm its makes the most noise.
Above 2000 rpm all nailing sound are gone and the engine is silky smooth.

I have tested the injectors all 5 spray on 115 bar (1667 psi) spray pattern is good.
Also did a compression test (cold engine) all 5 cylinders are around 31 bar (435 psi)

Last time i put some vegi oil to the diesel 50/50, didn't make it sound less.
Very sometimes the nailing sound is gone 1 on about 20 times for a brief period.

Does someone have any idea?

Some little history about the car.
I live in the Netherlands, and i imported the car from Germany.




The car is here at the RDW, they inspect the car if its not stolen and the identify of the car is proven, then i get the license, and plates to drive here.

The car was inside and outside....poor. The interior was completely bleach by the sun, 4 cracks in the dashboard. outside of the car are small dents, bumps and scratches.

The lady where i bought this car from was 91 years old. the car stood still for 1.5 years. Here husband bought the car new, but passed away in 1998.

I replaced the interior and dashboard, replaced all filters and fluids and tires.
This month the car gets a paint-job to repair the damage outside.

Welcome to the forum!

In my experience injectors nail when cold not hot. If they nail when hot they also nail when cold. And it's caused by the injectors opening too soon, ie pop pressure too low. I'm not sure that your injectors are supposed to be popping at 115bar, but someone here can say for sure. If you're injectors are popping correctly and the spray pattern is good then the noise is something else.

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That why i hope a expert recognize the sound on the youtube.
115 bar is correct.

My other thoughts are vacuumpump? Or the injection timing device gear on the pump?

or even stretch on the timing chain? i really don't know.

I have ordered LIQUI MOLY to do a purge.

Ill have to wait do the purge.
My car is getting a paintjob.

i have the same problem, i looked & listened to many 602's on you tube and all sound the same " nailing on idle " .
i changed my injector nozzles "bosio " still same, did purge, still same, engine run's great after 1800 rpm. drives with all the power it shoud have.
i have had no luck cureing mine & it seems all the ideas from folks trying to help have also not cured the noise.
i am taking to a Mercedes indy shop tomorrow to see what they recommend, im sure it will be many things that wont solve the issue.

Did either of you try re-timing the Fuel Injection Pump?

Is there any issues like Valve Lifters making a ticking noise.

Due to the fact that my Computer is not connected to a Cable I do not bother to view vids as it takes too lon to download them. But, is there a chance the sound you are hearing is not nailing?

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84 300D, 82 Volvo 244Gl Diesel

This is all I have in my notes about odd nailing problems.

Nailing Caused solved by Changing Delivery Valve Seals
A Question for the Injection "Masters" - PeachParts Mercedes ShopForum

Nailing caused by delivery valve.
http://mbca.cartama.net/archive/index.php/t-19002.html

Nailing after IP O-ring change
http://www.peachparts.com/shopforum/showthread.php?t=216067

Thread where Delivery Valve Seals replaced and Nailing went away almost
http://www.peachparts.com/shopforum/diesel-discussion/312510-delivery-vale-seals-my-ip.html

More Nailing List of causes
NAILING - Page 2 - PeachParts Mercedes ShopForum

Nailing stopped after solving air leak or removing air
Runs Rough In The Morning - PeachParts Mercedes ShopForum

Mystery nailing due to messed up secondary filter
A Question for the Injection "Masters" - Page 2 - PeachParts Mercedes ShopForum

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84 300D, 82 Volvo 244Gl Diesel

Thanks Diesel911 for the links.
Yes its most defiantly nailing sound. When its cold i can hear the Valve lifter for a brief moment, its a other sound.

I have done the purge a month ago, it did a little help, but 1-2 days later the sound came back. Positive effect the engine is more throttle responsive.

Today I have checked the transparent fuel line going to the main filter. The line from fuelpump(liftpump?) to the fuelfilter had some air in it when i gave it s bit throttle.
The other lines are ok.
In one of the note links the fuel-preheater can cause trouble, so i bypassed it.

Guess what, its much better now, and less air. But its still there. Also there is a huge air bubble in the pre-filter. So my next guess is the the tank-filter is dirty. Thats the next thing i want to clean.

There is always An air pocket at the high point on the clear PRE filter on more than one of my cars.

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