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  #1  
Old 07-15-2021, 01:03 PM
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OM603 Compared to the others

Thinking about picking up a local TDT wagon. What should I know about this engine? Thank you valued experts!

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  #2  
Old 07-15-2021, 02:13 PM
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From my experience with a NA 602 2.5:
1. Overheating a 60x motor is likely to crack the aluminum head.
2. Hydraulic lifters means no valves to adjust
3. Lots of little EGR vacuum lines.
4. Serpentine belt so with misaligned or worn idler pulleys, you can break a belt and lose cooling, see #1
5. Starts easy, pulls well when healthy, good MPG.

W124/201 plastic trim doesn't seem to age as well as W123 plastic trim. Don't be surprised if the plastic is extra brittle.
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  #3  
Old 07-15-2021, 03:24 PM
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Thank you. Carry a spare belt and the tools to put in on, and a diagram!
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  #4  
Old 07-16-2021, 04:08 AM
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Quote:
Originally Posted by INSIDIOUS View Post
Thank you. Carry a spare belt and the tools to put in on, and a diagram!

Just replace the idler pulley, spring, shock absorber, pivot, etc with factory parts and it will be fine. You can change the vacuum pump at the same time too, which also needs to be done, and put an om606 fan and fan clutch in.
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  #5  
Old 07-16-2021, 09:03 AM
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Quote:
Originally Posted by 83w126 View Post
Just replace the idler pulley, spring, shock absorber, pivot, etc with factory parts and it will be fine. You can change the vacuum pump at the same time too, which also needs to be done, and put an om606 fan and fan clutch in.
What is the test to see if those belt parts need replacing?
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  #6  
Old 07-16-2021, 09:50 AM
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What is the test to see if those belt parts need replacing?
Take the belt off and check each pulley for play and then rotate it and listen for abnormal noises.

Installing a one way alternator pulley helps if you have belt tensioner vibration.
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  #7  
Old 07-16-2021, 10:49 AM
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I had one in an 87 300d for a few years. I spent $1500+ in preventative maintenance (including the upgraded vacuum pump with less risk to the timing chain). In retrospect, I would have just driven it and only replaced the bare necessities. I sold the car for $1500. It ran great all the time I had it. Very good engine IMO. Mine still had the #14 head (the one that can crack if overheated).
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  #8  
Old 07-16-2021, 01:42 PM
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I like the engine all in all, but one does need to pay close attention. Quicker and smoother than the OM617, better mpg, but perhaps more delicate.

I had no way of knowing of course, but in hindsight the preventive maintenance I really should’ve done was to replace the original radiator with the all aluminum aftermarket unit. The radiator will self-destruct eventually.
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  #9  
Old 07-17-2021, 11:54 AM
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I've owned quite a few different non MB diesel engines - and two 603s. I like them very much. I like the power curve. Though I don't love the power curve with the auto gearbox so much. They are quiet and easy to work on. Predictable, if I may say. That idler pulley and spring and shock are failure points, but just replace them when they start to make noise. My complaint is that engine is long enough to make working on the front of it a pita. I've resorted to removing the radiator just to free up space and ultimately to save time. I am thinking about installing the all aluminum radiator. Here in southern Nevada the heat is a concern. My #14 head has almost 300k miles - so far so good.
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  #10  
Old 07-19-2021, 09:50 AM
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Yeah, that guy in Morrocco with the swapped 603 had length problems, I forget what it was swapped into, a W116 maybe?
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82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times
It's hard to
more likely to
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when you're on
at the same time.
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  #11  
Old 07-19-2021, 02:37 PM
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Thanks guys. Funny thing. The belt snapped about 1/4 mile into the test drive U turn and right back to parking in the drive. Was very old belt, Car had sat for years. Owner didn't know what a serp belt was. Looks tight in there, can I put on the replacement without dropping the engine?
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  #12  
Old 07-19-2021, 02:52 PM
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Remove the fan with the shroud and you will get more room.
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  #13  
Old 07-19-2021, 03:28 PM
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I'm going off years back on memory, but I don't think I removed fan or shroud to put a new belt on.
__________________
-E300d '99 350k

-Suburban '93 220k
-Diesel Jetta '03 350k

Sold
--E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia Missouri Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's!
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  #14  
Old 07-19-2021, 04:30 PM
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I have om603 turbo with almost 250k miles as daily driver.
I like it, it's not fast, but it's just enough to live in a big city. It's fast compared to om617 for sure.

1. Take off valve cover and check timing, then check timing relative to injection pump. Check chain slack if any.
2. Turbo seals like to go bad and smoke, I replaced the whole turbo on the cheap and it's been fine.
3. EGR delete is a good thing to do.
4. Blowby...a little is ok. It likes to spit a bit of oil around turbo, that's normal.
5. Delivery valve seals, sooner or later, plus make sure the hard lines from IP to injectors have all their plastic holders. There's a lot of vibration and they are a must!
6. Other than that, as others mentioned, belt and belt tensioner is very common failure point.

Usually these engines are really good, I have the #14 head and no issues even when car got to 110 degrees.
Typically your transmission or axle shafts will go first rather than this engine

If you are getting this car, I highly recommend doing LiquiMoly Engine Flush right before first oil change.
Then, of course, Diesel Purge with all new filters, as you probably know It really makes a huge difference for city drivers
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  #15  
Old 07-19-2021, 05:11 PM
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Quote:
Originally Posted by filp View Post
I have om603 turbo with almost 250k miles as daily driver.
I like it, it's not fast, but it's just enough to live in a big city. It's fast compared to om617 for sure.

1. Take off valve cover and check timing, then check timing relative to injection pump. Check chain slack if any.
2. Turbo seals like to go bad and smoke, I replaced the whole turbo on the cheap and it's been fine.
3. EGR delete is a good thing to do.
4. Blowby...a little is ok. It likes to spit a bit of oil around turbo, that's normal.
5. Delivery valve seals, sooner or later, plus make sure the hard lines from IP to injectors have all their plastic holders. There's a lot of vibration and they are a must!
6. Other than that, as others mentioned, belt and belt tensioner is very common failure point.

Usually these engines are really good, I have the #14 head and no issues even when car got to 110 degrees.
Typically your transmission or axle shafts will go first rather than this engine

If you are getting this car, I highly recommend doing LiquiMoly Engine Flush right before first oil change.
Then, of course, Diesel Purge with all new filters, as you probably know It really makes a huge difference for city drivers
Thanks for that effort. Regards 2. Would that smoke be on start up or while at operating temp, all the time?

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