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Mercedes Intake Seal Ring Replacement


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All parts used in these pictorials are available at the diesel parts for sale page


Safety and security tips:

Please remember to recycle all your used fluids at an appropriate recycling center.  Be mindful to not spill or splash fluids on yourself, others or the ground.  Also as a safety tip please remember anytime you are working on, around or under your car, to wear safety glasses and secure the car with wheel stops and approved jack stands!  


Mercedes Intake Seal Ring Replacement for the Turbo Diesel


This is one of those projects that most people never give a second thought, but has really been nagging me for a while.  For many years, without exception, every single turbo diesel Mercedes that rolled through my shop had less than stellar sealing rings.  I can say that they all were the original and hard as a rock.  After removing the U shape boot, most of them were not even aligned properly.  I did my best to realign them, but mostly to no avail.  The sealing rings are like a giant O ring, when they are soft and pliable, they seal.  When they are rock hard, brittle or misaligned, they don't seal worth a flip.

It does not take a mechanical engineer to realize that if the rings don't seal properly, then unfiltered air IS getting into the turbo and intake, without passing though the air cleaner.  Mercedes built an engine that is one of the most robust and will certainly take a beating, but why add insult to injury with unfiltered air.  Another benefit to replacing the sealing rings is, you may notice the oil drip from the bottom of the intake boot where it mates to the turbo stop.  Why?  Because the oil residue is now being burnt in the engine and not slipping past a non sealing ring.

So follow along as we do a rather quick project, but very important.


These are the 2 sealing rings.  The larger one mates the intake, the smaller one mates to the turbo.



A 10mm socket and long extension with a universal is about all the tools you will need.



The U shaped boot is what we are going to remove.



Remove the air intake extension to get more working room.






Remove the clamp on the turbo side of the U boot.....



Remove the clamp on the air cleaner side of the U boot.....



Pull the U boot free.



Some oil and a misaligned seal ring.  Hmmm that was not sealing very well was it?



This is how the ring sits on the air cleaner.  The grove in the seal ring fits into the ridge on the air horn.  But this is not how you will be installing it.




This is the most difficult part of the job.  If you install the new ring all the way into the U boot and try to install it, it will push past the mating point or will go on crooked and misaligned.  Just what we want to avoid.  After many trial and errors, I figured out for you, how to do it properly.  Slide the sealing ring into the boot and leave a little less than 1/4 inch sticking up.  This is just enough so that when you slide the boot back on, the ring will push down into the boot and line up correctly.

I tried doing this many different ways, but they never allowed the ring to sit square in the U boot. 

Don't install the U boot just yet.  We have to put the turbo seal ring in the boot first.



The old turbo sealing ring will most likely be the hardest to remove from U boot due to the higher heat at the turbo, making it nice and brittle.  Just use some needle nose pliers and break it in half and pull it out.



Push the new turbo seal ring in the U boot.  Just push it all the way in until it seats.  Since the turbo surface is smooth, it goes on with out much struggle.  When installing the U boot just line it up square with both the turbo and the air cleaner and give it a good push.  It will be really hard to go on, unlike how it was with the old hard rings.  But, you will actually have all the air going into the intake, filtered by the air cleaner, instead of leaking past some old sealing rings.


When its on properly, the U boot sits square with both the turbo and the air cleaner.  Look at where the stop ridge is on the air cleaner, that is near where it should rest.


Now that was not so hard was it?