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  #1  
Old 04-12-2015, 03:56 PM
nyko46's Avatar
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Location: Rowlett - Texas - USA
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Question Injector Leakage On Cylinder Head

My 1984 300 SD has a small diesel leakage mixed with engine oil at the "sleeve" (that threaded scored piece) where the fuel injector is threaded to at the cylinder head.
Just to make sure the leak is from there I cleaned that area with carburetor cleaner and let it dry. After driving the car for two days I check it again and and found wet the base of fuel injector at the cylinder head. Fuel return lines and hoses are new and no leaks there. This problem is on the cylinder #3 and #4. What is the best DIY to have this leak repaired?
If no special tool is required I have a lot of metric tools to work on Mercedes.
Thanks

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  #2  
Old 04-12-2015, 07:13 PM
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Sounds like a leaky heat shield.....Rich
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  #3  
Old 04-12-2015, 08:05 PM
Diesel Preferred
 
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Location: Charleston SC
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What work was done there recently? The return lines are always the prime suspect, feel them for fuel wetness. If the old lines were removed by cutting them off, the nipples may be scored and will always leak.

Are the fuel return lines covered with braided cloth?

It is also possible for fuel to leak from between the two halves of the injector body, but this does not occur spontaneously. It is common to have leaks after injectors are rebuilt, but once they are leak free, they are good for a long time. Dirt or grit can get onto the sealing surface and prevent a good seal. If this is the case, they must be taken apart, lapped on a flat until the defects are gone, cleaned and put together and tested again.

I'm also sceptical that a heat shield is responsible, unless the injectors were not properly torqued down.
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'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
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  #4  
Old 04-12-2015, 10:10 PM
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Question Heat Shield

These injectors were installed about 2.5 years ago and the leakage was not there. I was the one who installed the injectors and I had special attention for all possible leaks. When installing I also install new heat shield on all five injectors. Return lines are all new and in good condition as well all injectors fuel lines.
Just in case I will clean again all areas of the injectors and see if there are some not noticed leak. Better saying, if leakage is from somewhere else other than described on my thread.
I will inform what I found.
Thanks to all.
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  #5  
Old 04-12-2015, 11:27 PM
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Spray the 2 Injectors down with Brake Cleaner so they are entirly dry. Run the Engine and wipe a Finger around the Injector from the top down and see if you can feel any wetness from the Fuel Leak.

Do that again and again over the course of 15 minutes and see if you find a leak.

Between the Injector Body and the Prechamber Retaining Ring there is a little bit if empty space. Fuel leaks and Oil leaks from the Valve Cover pool in that space.

When the Engine is running that stuff can sometimes bubble and appear to be a leak when in fact it is bubbling from the shock waves created by injection and combustion.

In your case there may only be enough inside to get the threads wet.

About all you can do about it is to try to fill that space with something that will displace the Fuel/Oil mix. Brake Cleaner works and Carburatorn Cleaner may also work if you flood the area and let it soak in and wipe it off and repeat that. Eventually part of what is left is going to evaporate or be to heavy to migrate from where it is.

Injectors can also leak around the little hose Barbs from knicks on the OD of the Barbes or at the base of the Barbes where they are swedged in they can develop a leak. The normal cure for that is to replace the upper Injector Body but that requires the Injector to be pop tested.

One of our Members cut the Niipple off and welded over where the nipple is and moved that one to the #5 spot.

If the Heat Shield is bad generally you have a small amount of Combustion Gas coming out and that would not leave your Injector Base wet.

You do need a special Tool to remove and more importantly torque the Prechamber Retaining Ring. You need another Special Tool to remove the Prechamber itself if that needs to be done.
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  #6  
Old 04-13-2015, 08:53 AM
Diesel Preferred
 
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If not the return lines, next I would suspect that you have a problem with one of the hard lines. Are all of the hard line holders present? Are the nuts attaching hard lines to tops of injectors tight?
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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
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  #7  
Old 04-13-2015, 10:18 AM
funola's Avatar
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Quote:
Originally Posted by nyko46 View Post
My 1984 300 SD has a small diesel leakage mixed with engine oil at the "sleeve" (that threaded scored piece) where the fuel injector is threaded to at the cylinder head.
Just to make sure the leak is from there I cleaned that area with carburetor cleaner and let it dry. After driving the car for two days I check it again and and found wet the base of fuel injector at the cylinder head. Fuel return lines and hoses are new and no leaks there. This problem is on the cylinder #3 and #4. What is the best DIY to have this leak repaired?
If no special tool is required I have a lot of metric tools to work on Mercedes.
Thanks
You don't want to wait 2 days after cleaning/drying to check for leaks, by that time the fuel has spread all over from where it originates.

After cleaning /drying, wrap all suspect leak areas tightly with toilet paper, start engine, wet tissue is immediately visible and pinpoints where fuel is leaking from.

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