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1982 300cd
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20 Posts
Discussion Starter · #1 ·
Hi,
It appears I’ve sprung a leak. I’m a little on the fence over attempting to tackle this problem myself or finding a professional to address it for me. But I defiantly wanted to check in with you guys before I jump right in. Here are the culprits.
Water Steering wheel Automotive tire Motor vehicle Coil
Automotive tire Steering wheel Steering part Motor vehicle Vehicle door

the last injector is defiantly leaking, once the engine warms up, it appears to be from the body of the injector. And the one next to it, may also be leaking, closer to the base, or just appear unclean because it’s next to the problem injector. (But I don’t want to clean my engine while I know there is at least one leak in the system.) Reading the older threads it sounds like before replacing the injectors, (redone in this car in ‘19) I should try tightening the body of the problem injector and then replace the crush washers on all of the injectors? Dose this car have crush washers instead of o rings or in addition to? What all would you say I should order before starting this project. And what is the best way to go about tightening the injector body? And are there any other points of advice you feel it would be important to keep in mind when removing injectors and hunting for leaks. Is attempting such a project with a fairly amateur skill level risking doing harm to my car, or is it something that is ok to address myself? Should I just replace the end cap on the last injector first, could it be that? (And is there a best cap to use.) I can’t tell exactly where the leak is coming from, but it seems prudent to start with the smallest possible culprit to fix and work my way up.
Thank you guys for any advice, and sorry for this post being on the longer side.
 

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1982 300D Turbodiesel (US Spec)
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333 Posts
It looks to me the leak may be coming from the return line, I see wetness in the flexible hoses. Just to make sure you don’t do unnecessary work, just replace the return lines and the cap in the end, clean everything and see if that solves your problem. If not, see if the metal hard lines are tight.

If the leak continues, then you will have to take the car to a diesel injection shop or remove the injectors yourself and take them to an injection shop to be cleaned, reassembled and tested.

Usually injectors don’t spring leaks from one day to another, they usually leak after they are taken apart following a rebuild. That’s why I think the return lines are your culprits and not the injectors.
 

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W123 300CD, W123 300TD, W202 C250D Turbo
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679 Posts
Luis is spot on.

Also, I would wash the engine with the leaks as it is easier to work on (not a greasy) and you get a better idea of where the actual leak is. You wont get water contaminating the fuel system.
 

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1982 300cd
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20 Posts
Discussion Starter · #4 ·
Thank you I will try that first, and hope that fixes it. I appreciate the insight.
 

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1979 Mercedes Benz 300TD 4spd Manual (Euro)
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107 Posts
I recommend buying the grey return line hose from a Mercedes dealer. I finally did so and it’s way better! Proof is in that my injectors are split at the moment between the grey line and black and the only lines that have leaks are the latter.
 

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1984 300D
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5,537 Posts
You don't need and end cap. People typically use as short piece of return line to make an end cap by inserting something in one end. I coat the threads on a screw with automotive type silicon sealant and shove it in and let it cure for a few hours and install it on the Injector nipple.

Former owners have been known to take a knife to cut the return lines off of the nipple. If the nipple is scratched enough it will leak.

If the Injector is leaking between the lower and upper 1/2 of the Injector it can be removed and the end Nut retorqued. If that does not fix the leak look for a hair line crack on the end nut. After that the Injector Nut end nut needs to be removed and the interior parts inspected and lapped again, re assembled properly and the end nut torqued prooperly.
 
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