OM642 Injector Seal Leak (ML320 CDI) - PeachParts Mercedes-Benz Forum

markg612 · #1 06-17-2017, 03:05 PM

Just finish replacing #2 injector seal, not as bad as some have claimed, and YES it was damn frozen/seized from the black discharge.

Ordered all I needed, as per usual from Importec. Bolt, copper seal and leak seal, AND the Febe ceramic grease that MB gets $29.99 for for a whopping $6.

Importec's primary wholesale source is SSF Imported Auto parts. They stock more OEM MB parts than anyone on the web, and Importec is and has been for along time the best price and service I've found.

Acetone is a must as is carb cleaner--I prefer CRC or Gumout or a combo of both. Brake cleaner, either chlorinated or otherwise won't touch the black. A post I saw on another forum, the guy used oven cleaner. UGH!

Lubed it up really good with penetrant and carb cleaner and chipped away and vacuumed up as much black as possible.

Tools: While a line wrench (18MM) will easily work for the rail nut, the injector line nut really needs a line socket (17MM) or you will bend the leak return line like I did. I bought an injector seal puller on ebay for $23 and an injector bore cleaning kit for $49, both are a must, as well as a injector slide hammer. I was able to rig an alternative means of attaching it to the injector with out damage, but the thread adapter on the 642 is a must. 648 iterations injectors are easily
grabbed with the slide hammer kits, but the head cover webbing precludes anything but grabbing the injector via the threads with an adapter of sorts. I also bought a compressed air vacuum brake blender, replaced and replaced the hose with a larger clear vinyl one. One can vacuum flammable solvents with a shop back without potentially burning or blowing yourself up.

Started with the engine smoke'n hot lava hot, and it made all the difference. The T40 headed yoke stretch bold came out like butter, and the leak lines after being sprayed with silicon lubed popped apart without any breakage, the heat definitely makes them softer and more easily operated.

The injector was a bit of a pill, it was tight as two fingers in a frogs ear and didn't budge with my first slide hammer attempts, which required replacing the hold down yoke without the screw and using a very large screwdriver. An EXTREMELY gentle prying on the yoke to twist the injector while hammering loosened it up like nothing. Gentle hammering finished the job and pulled it free.

The rest was cleaning and polishing with the bore cleaning kit, lots of acetone and carb cleaner and a tooth brush. The injector came clean with only acetone, and the tip sealing surface needed to be reface from the burn etching from the seal failure. I used fine emery cloth, poked a hole in the paper and drilled a hole in a piece of 1/16" aluminum and polished the mark off the face. It is imperative to ensure the bolt hole is perfectly clean all the way to the base. Any material in the hole could potentially cause the retaining bolt to push a hole into the water jacket and now you've got another PITA problem to deal with.

Lubed up the injector shaft with the ceramic grease, dropped the seal in the hole and ensured it was positioned correctly, CU800ed the bolt treads and mating face of the yoke, slipped all the now loose fitting pieces back into place, torqued to 7nm, with two additional 90º turns to stretch the bolt, leak lines back on, job done!

I'm having issues posting pictures will do so when resolved.

markg612 · #2 06-17-2017, 03:14 PM

Couldn't get them to post in the original thread.

dmcampbell · #3 01-08-2018, 06:53 PM

Mark: How long/miles do you suspect the injector seal was leaking? Also, do you think a injector seat cutter would help? My #1 injector is leaking, but plan to replace all seals. Thanks, Mike

Diesel911 · #4 01-09-2018, 12:50 AM

Did you replace or face the surfice on the Injector Nut?

markg612 · #5 01-09-2018, 10:32 AM

YES, I faced it with a tool I fashioned.

I used an 1/8" thick piece of aluminum and drilled a close fitting hole slightly larger than the tip of the injector, then used multiple grits of emery cloth and then sandpaper, cut the same size hole in the paper(s), lined up the holes of the paper and aluminum plate, put the injector tip through the hole and turned the injector against the paper until the burn was smooth again. (See the photo next to the one where the seat is burned) Had I attended to this sooner, I don't believe the burn would have been as deep.

You need to use a very hard backing stock for the paper to ensure the face stays true.

Does that help?
G

markg612 · #6 01-09-2018, 10:33 AM

Quote:

Originally Posted by dmcampbell

Mark: How long/miles do you suspect the injector seal was leaking? Also, do you think a injector seat cutter would help? My #1 injector is leaking, but plan to replace all seals. Thanks, Mike

Hey Mike, it had been leaking a while, maybe 6 months to a year. It stunk the garage up really bad, it started out with just a hint of aroma and as the months passed, I couldn't stand the smell if put the garage door down after we drove it before it cooled down.

Also, the insidious bit was the not perfectly smooth feel of the engine?? my OM648 is like glass, and every power pulse is even, the OM642 was noticeably less smooth pre-repair, now's it peppier and decidedly smoother, to the point, much like failing engine mounts, one doesn't realize how bad they are till they're fix.

I don't know that a cutter is necessary I used a seal puller,(ebay purchase) which requires a bit of finesse to grip the bad seal properly, and I'd a never got it out with out it.

Sooooo, I would highly recommend against futzing with any injector that's not leaking. the injector fits loose into the head bore and at the yolk and stretch bolt lock it down against the seal, so if it's leaking you're going to get black schmutz around the injector at the head rather quickly after it starts leaking, and most likely you'll get that engine oil/diesel stench too. It's a lot like a tire or an injection line, the injector seals either seal or they don't. I'd highly encourage not to messing with an injector until it shows black death schmutz, however, there is the piece of mind, don't want to deal with it later aspect too.

I've been nearly 280,000 miles in total between both engines, and I've only had the one 642 seal fail. Strangely enough, I've put 3 glow plugs in the 648 and none in the 642??

Acetone and carb cleaner(especially the non-CA types with toluene) melt the black schmutz like butter under a blow torch. Brake Cleaner from Red states (Communist ephing California banned chlorinated solvents, so i smuggle them in from NV or MN) works with compressed air to dry everything, after it's clean.

PS, I have to say that injector bore cleaning kit I bought on eBay was a complete must. I resurfaced the injector seal seat and completely cleansed the injector bore to Stutgart new perfect, and without it, I don't believe it would have been that simple.

Does that help?

Mark

Diesel911 · #7 01-09-2018, 10:40 AM

All sounds like a good job.

Sometimes lapping as was done is better then using a cutter is better because you remove less material then you might with a cutter.