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Discussion Starter #1
I decided to change my engine when it had around 270K miles. There were several reasons I decided to (besides finding an engine with ~100K miles for $300). Keep in mind the ML was bought with 179K miles.

  • It began idling very rough (motor mounts)
  • It died while I was pulling into traffic (traffic going 50mph) :eek:|
  • MAJOR oil leak at the rear main seal
  • Extremely sluggish acceleration
  • Upon checking spark plug, one was covered with oil at the ignition side
I did a check the typical suspects including checking the plugs which were good and fairly new, EGR system was clean from build up, air filter was good…there was however, some oil on one of the plugs at the cylinder/ignition side upon inspection.

I weighed spending the time and money to troubleshoot different parts versus the age and mileage (especially with the failure in the rear main seal). As I would have to either remove the engine (or transmission) for the repair of the rear main seal, I decided to just go a head and change the engine, and it was a great choice! She runs great! Plus, this gives me the spare to rebuild with the boys :wink

Helpful Thoughts and Finds Along the Way
I found that removing the wires from the electronics box (versus from the engine itself) made things very simple. It also allowed for the installation of said wires from the original engine onto the new engine outside of the engine bay, which there was obviously more room to work. I used a video MERCEDES ENGINE WIRING HARNESS REMOVAL REPLACEMENT ENGINE by Auto Repair Guys
for reference:


Unbolting the bell housing was straightforward. I did need two wrenches, one for each side of the bolt. The bolts on the flywheel were a little tricky as I had to turn the torque converter by hand.
 

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Discussion Starter #2
The rear main seal was a little tricky. A couple of years ago I bought some of the gasket maker from the mothership, which ended up being runny and didn’t want to dry. I went to a local, and trusted, indie shop (engine in the back of another vehicle) and for $20 got a first hand insight how to change it from a former Mercedes mechanic. The whole process took about 15 minutes.

He used the black RTV and put a thin coat on the plate of the rear main seal. He got just a little RTV on his finger and made a thin layer on the plate rear seal plate (the plate, he said, has to be replaced with the gasket). He also (and he said this was the important part) used Permatex aircraft glue (from O’Reilly’s) and put a thin coat on the engine block. He said this was help prevent premature leakage….I’m sure it will take some work to get the plate off in the future! Lol

Keep in mind that once the plate off, all of the oil will be able to spill out!
 

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The replacement engine did not have the air intake manifold, bought $8 gasket set from O’Reilly’s, swapped it out and was good to go!

And, as mentioned, the motor mounts were awful! Also, make sure to get the correct CPS sensor! There are some out there that say they are for a 98 ML320, but not legit!
 

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All in all, It was a fairly straightforward process. The only real frustration arose with the pairing of the engine to the transmission. I tried by myself (just to see if I could) with no avail, and It ultimately took two of us and about 10 minutes later the new engine was aligned!
 

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Good job.

You are lucky that you do not live in Sacramento county.:eek

https://www.benzworld.org/forums/w140-s-class/3031358-what-hell.html#post17833538

It's interesting isn't it, how a person can own their house....but do they really own it when people can tell said person that they can't work on their own car on their own property?!

California is ridiculous! Have you heard of the vehicle mileage tax: https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201720180SB1328
 

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1998 ML3rry puxkwr20 Engine Swap

I have aswell performed a 98 ml320 engine swap.
My ?'s:
After performing the swap has anybody else had any limp mode issues? I do. What I've done so far is replace conductor plate, and tcu that i got out from the same 99ml320 I got the newer engine from.
Result: no longer slipping at first acceleration from a stop but still appear to be unable to reach higher gears( feels like 3rd,4th, 5th) and shifts occur in my opinion at a much higher rpm(4,5)and don't seem when in drive to ever really drop to 1or 2 rpms. However in park or drive when at complete stop the idle is perfect. I bought the trans dip stick to have a adequate reading of my atf level and I'm certain I'm good. Any suggestions?
Here is the other explanation for what I might have mentioned earlier if not first of all is that I have this to much of a coincidental misfire on 4,5,6 cyclinders which are all on the same side leaving me to believe that something sensor or ground re lated is re sponsible. But which one or where and how ? If any one has some input I'd appreciate it. Please do not respond with ?'s just suggestions and/or ideas. Thanks
 

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You need to pull the codes from the ecu and tcm read them and then clear them all. Take it for another drive and check it again if it goes into limp mode.
Your miss fire could be blocked cat. Swap the coils with some off the other engine.
Sorry if this comes across as an idea or suggestions but it’s kinda how we work through problems. It’s hard when your not actually there doing the job.


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