Hello diesel people, wanted to share my experience with repairing our bluetec. It has been marking its territory with increasing volume, so it was time to take corrective action. Apparently Mercedes used gaskets of an inferior material for the oil cooler, which after some miles and years will result in an oily mess all over the engine, and give the entire underbody a solid winter rustproofing layer. Making matters worse, they buried the oil cooler as deep as they could. What I expected to take a few hours, ended up taking the entire weekend. A full day of disassembly, and another full day of cleaning and reassembly. Wow I sure hope the mystical powers of these magic purple seals don't wear out any time soon. I would not like to perform this job a second time.


The resources I found most helpful as a first-timer performing this job:

• A journey into the the infamous Om642 oil cooler leak!
• https://www.youtube.com/watch?v=l1IslZzL3vU

A few notes, based on a number of discussion threads and youtube videos:

• Definitely replace the EGR cooler seals while you're in there. One small o-ring, one larger o-ring, and one gasket.
• Replace swirl motor if yours is in-op as mine was. I also made a poncho for the new one, out of aluminum foil, to prevent oil intrusion.
• Good time to replace the water pump, belt, tensioner, rollers. I used a genuine pump from the dealer at over $200 as I've heard the aftermarket pumps use lower quality bearings, that's why they cost so much less.
• Check your right side intercooler hose for crack/leak in the rubber near the upper collar. Mine had a crack and pin-hole leak there.
• I read some folks like to remove the firewall heat shields for more access to the turbo fasteners. I did not, and did not find it necessary. There is plenty of access, nice straight shot to all of them.
• I wish I had found the aftermarket aluminum intake flap arms. I didn't discover these until afterwards. idparts dot com sells them, to replace the brittle plastic ones with.
• I replaced the entire oil cooler with a new one, not just the seals. Not sure this is necessary, but I didn't want to take the chance that the cooler itself had some kind of failure.
• I'm now a fan of these external torx fasteners! The sockets really grip the fastener well, the chances of slipping and rounding one off seems much reduced with these.
• Also now a fan of the fuel line hose clamps. People in the youtube videos pry them off like savages and replace them with inferior worm drive clamps. These factory ones are re-usable and the correct tool allows them to be very quickly and easily opened and closed.

I think thats about it for random thoughts on this job. Nothing really technically difficult, just a lot of steps, very time consuming. I also pulled all the glow plugs since the access was good. I cleaned and lubed them. Hylomar on the body and copper anti-seize on the threads. They all still work, but they're original, just wanted to ensure easy removal when they do require replacing.


Cheers

__________________
Current fleet:
1998 E300 turbodiesel
2008 E320 bluetec - leaky oil cooler seals replaced
2012 S350 bluetec
2014 GL350 bluetec

Sold:
1996 Passat TDI
1997 E300 diesel

Looks like my thread finally was approved. It was held for moderation for some reason. Anyhow, I took tons of photos along the way, mainly to help with reassembly, so if you're stuck on a specific step and need some photo reference, just let me know.

FYI for cleaning the intake manifolds, I used the propane torch method, it works really well and it's faster and easier than using chemicals: https://www.youtube.com/watch?v=xIijYgvxW0g

__________________
Current fleet:
1998 E300 turbodiesel
2008 E320 bluetec - leaky oil cooler seals replaced
2012 S350 bluetec
2014 GL350 bluetec

Sold:
1996 Passat TDI
1997 E300 diesel

Thanks for video link.

__________________
Jim

Some more photos from the job.



EGR cooler, showing location of the service items. One large o-ring, one small o-ring, one gasket. Replace while you're in there!! or you'll be doing the entire job again later when the small o-ring or gasket begin leaking. The EGR cooler itself appears to be made of stainless steel, looks/feels very high quality, it should out-last the car.


Another good WYIT (while you're in there) item. Belt, tensioner, and two rollers. The tensioner and rollers have 120k miles on them, so it's time to replace. Access is good, so now's the time. The old rollers were clearly bad once I had them off, they rattled and had zero grease left in the bearings. There were no symptoms while driving, so these will eventually fail without warning, throwing the belt and leaving you stranded. For replacement belt, I went with Gates "Green Stripe" Fleetrunner which is intended for Sprinter Van fleet vehicles. It's supposed to be an extra long-life belt as compared with the standard Conti replacement.


The intakes, after cleaning them out with the propane torch method. Crud was modest for 120k miles, but they're a lot cleaner and free flowing now. Clean the mating surfaces well before you bolt them back on, and use new gaskets. The intake manifold gaskets are made of metal and have nice clips that hold them in place during reassembly.


Pile-o-parts, this is everything you must remove to reach the oil cooler. Nothing difficult, just lots of hours to reach this point. Since the coolant is drained for this job, consider also replacing the water pump and the coolant hoses at the front of the engine. Access is very good with everything disassembled. The hose part numbers are 2115015482 and 2118327794 and 2115018682 for this 2008 E320.

__________________
Current fleet:
1998 E300 turbodiesel
2008 E320 bluetec - leaky oil cooler seals replaced
2012 S350 bluetec
2014 GL350 bluetec

Sold:
1996 Passat TDI
1997 E300 diesel