How terrible is the OM642? - PeachParts Mercedes-Benz Forum

iwrock · #1 06-14-2016, 12:41 PM

I've read that they have some issues with swirl motors, oil coolers, and motor oil suddenly thickening... Other than these oddly expensive issues, are they pretty reliable? I'm considering replacing my C230 in the next month or two, and an ML CDI is at the top of my list for replacements. (A GL320 CDI is also up there)

jay_bob · #2 06-14-2016, 07:38 PM

If you are used to a 617 you will not know where to start when you open the hood.

It is a giant rubber band ball under a big cover.

Working on it is like an onion, you have to peel back the layers to get to things.

I have had my ML 3 years now, put about 35k miles on it, (it has 138k on it now) and only had 2 big issues.
One was the glow plugs failed, and it required changing all 6 and the controller since they redesigned it. I elected not to go DIY on this one since I was traveling for work when it happened. $1500 at the dealer.
The second failure was the cam sensor. Luckily the ECU threw a code before it totally died and left the car inoperative. That one was under $100 and easy to change.

I have done my own oil, air, and fuel filter changes on the engine, it's not too bad.

They do suffer from a leaking seal at the turbo inlet. This causes blow by to drip down on the ground under the car and leaves embarrassing spots when you park.

When the oil seal failure happens there is an excellent write up on the forum, it just requires a week of vacation to get it done if you DIY.

Try to get an 08 ML or older, the newer ones have AdBlue which removes the spare tire so they get run flats. The particulate filter means that you cannot get it to roll coal under any circumstances, the computer won't let it have too much fuel and the filter cleans up the rest.

iwrock · #3 06-14-2016, 07:50 PM

Quote:

Originally Posted by jay_bob

If you are used to a 617 you will not know where to start when you open the hood.

It is a giant rubber band ball under a big cover.

Working on it is like an onion, you have to peel back the layers to get to things.

I have had my ML 3 years now, put about 35k miles on it, (it has 138k on it now) and only had 2 big issues.
One was the glow plugs failed, and it required changing all 6 and the controller since they redesigned it. I elected not to go DIY on this one since I was traveling for work when it happened. $1500 at the dealer.
The second failure was the cam sensor. Luckily the ECU threw a code before it totally died and left the car inoperative. That one was under $100 and easy to change.

I have done my own oil, air, and fuel filter changes on the engine, it's not too bad.

They do suffer from a leaking seal at the turbo inlet. This causes blow by to drip down on the ground under the car and leaves embarrassing spots when you park.

When the oil seal failure happens there is an excellent write up on the forum, it just requires a week of vacation to get it done if you DIY.

Try to get an 08 ML or older, the newer ones have AdBlue which removes the spare tire so they get run flats. The particulate filter means that you cannot get it to roll coal under any circumstances, the computer won't let it have too much fuel and the filter cleans up the rest.

Thanks for the info! I personally haven't had an OM617, but have friends who own/wrench on them - and have assisted. I've worked under the hood of a G500, E55, C230, and a few other newer MBs, so peeling the layers of onion to fix things is nothing new! Admittedly, I've got a friend who is an MB tech, and does wrenching on the side relatively inexpensively - so if there's anything major in need to repair, I'll just farm it out.

An 07-08 CDI was actually the model I'm considering. After watching friends having to deal with DEF on their Powerstrokes/Duramaxes/Cummins - I've decided to just avoid it and go with a CDI. The 09+ does have a better infotainment system (does Bluetooth audio out of the box) and seem to return a little better fuel economy, but the possibility of getting stranded due to low/no DEF is pretty annoying.

What sort of fuel mileage do you get out of your CDI? Do you ever use it for towing?

babymog · #4 06-14-2016, 08:45 PM

Stranded due to low DEF? Carry some, you can buy a liter from your dealer for around $10, ... put it in the spare tire well.

I don't know about the '08s, but the new ones will let you know 20 starts before it runs out, plenty of time to get DEF at any truck stop or parts store.

KrustyKustom · #5 06-14-2016, 10:51 PM

I have two of these OM642 engines, one a 2011 GL350 and the other a 2012 Sprinter van. I have 96k on GL and 82k on Sprinter and have good service from both. GL has had more issues, timing chain replacement , oil cooler seals. Sprinter has been flawless.

It's all about the maintenance and never using greater than B5 bio diesel which causes sludge. Mine are spic and span inside, I never go full interval on oil changes. The drawbacks to the pre def cars is they had more leaks for sure. The later engines have had many part revisions to egr and crankcase ventilation systems.

Check out Sprinter forums, lots of engines over 450k and some over 600k.

jay_bob · #6 06-15-2016, 06:31 AM

I get low 20s in town and mid 20s on highway trips.

The 08 ML320 is rated 7000 lb towing capacity. I have pulled a 2000 pound trailer and it was unnoticeable back there.

Note that the ML has a 7 pin connector, but if you have a trailer with LED lights, be sure to get a 7 to 4 adapter that has ballast resistors, or the car computer will go crazy, since it cannot detect the LED bulbs properly. They have them at e-trailer dot com about $15.