Injection timing the OM617 turbodiesel - illustrated - Page 2 - PeachParts Mercedes-Benz Forum

suginami · #16 10-06-2003, 02:43 PM

About the 3.0 liter six cylinder diesel engine in the later W126 cars - I know that most here on this site are concerned about cracked heads and overheating on this engine, but I've discussed this with the legendary Enrique at Mr. MB Motors in Southern California, and he swears that the newer engine is a better engine than the five cylinder, and doesn't have a high failure rate of cracked heads and overheating.

mplafleur · #17 10-06-2003, 02:49 PM

I've got a clamp-type tool, but the clamp is the wrong size. It's an AVL 875 and the manual is in German.

Thomas,

I'll lend it to you if you can send it back with the right clamp and a translated manual.

leathermang · #18 10-06-2003, 02:59 PM

RLeo is always smarting off in GERMAN.. lets make him translate it... LOL

R Leo · #19 10-06-2003, 03:21 PM

Der Unterschied zwischen gescheitem Deutschem, das von den Computern und von Deutsch übersetzt wird, die intelligent gesprochen wird, ist sehr groß.

leathermang · #20 10-06-2003, 03:26 PM

THAT DOES IT ! Send the manual to Randy....

mplafleur · #21 10-06-2003, 03:44 PM

I just got off the phone with AVL. They have an office a few miles away that they didn't have when I bought the unit. Someone there is going to try to find a translated manual as well as the correct size clamp.

6.35mm right? or is that what came with it and I need 5mm?

What size is that inj line?

jbaj007 · #22 10-06-2003, 04:58 PM

6.35 mm is 1/4" inch and I heard that is not for our cars. I assumed 6 mm. from another website, but I'll throw a "mic" (pronounced "mike"

) on a line tonight and let you know what I get. I'll bet AVL will get back to you with the exact answer for Mercedes as I thought it's a German company. Dieselmota (something like that) is a guy (on some BBS's and on eBay) who imports a lot of German stuff, including AVL stuff. He'd know the size.

Edit (later that evening)

I measured 5.95 mm., so I assume the 6.0 mm. is the one to buy?

Thomaspin · #23 10-06-2003, 05:45 PM

I have updated the slides for Dave M's comments. Thanks again Dave.

gsxr · #24 10-06-2003, 05:52 PM

Quote:

I assume you still have to pop the valve cover to determine chain stretch. What's the key test to determine if the engine has overheated - compression? And why is the six so prone to overheating?

Yep, still pop the cover to check stretch. But on the 603, it's easier & cleaner, IMO - no linkage to mess with either.

As to how to test for past overheating, there's no test that I know of. There is a rudimentary test for the result of overheating - the dreaded cracked head. To test, open the radiator cap with the engine COLD to release any pressure and equalize the system. Then fire it up, warm it up, and drive the car hard - numerous full throttle trips to the redline. Run it as long and as hard as you want. Then park it overnight. The next morning when COLD (same ambient temp as previous day, approximately), pop the hood and squeeze the upper radiator hose. It should be soft and squishy, as if the cap were removed. If so, the head is probably fine (assuming there is ZERO coolant loss). If it's rock hard and tight as a banjo string - can't pinch at all - there's an excellent chance the head is cracked. Figure $900 for a used head, $1800 for a new one (bare), and either a couple hundred bucks in tools as DIY, or ~$1000 labor at a shop. I like these engines so much, I think it's worth it, if the problem happens during ownership just eat the cost and fix it. The new heads are stronger and shouldn't crack in the future.

Why do they overheat? Well, the cooling systems are the common fault, often from not using MB coolant and not changing it frequently enough. Also the fan clutch has a finite life span as they slowly spew the silicone fluid out and stop working properly. You can re-fill the original fan clutch (with metal blade), the new replacement clutch (from the OM606, with plastic blade) may not be refillable. Well, nobody has figured out how to refill the new one - yet. Keeping the fins clean to ensure good airflow is required, and testing operation of the electric fan & it's triggering senders is a good idea as well. When shopping for a car with a 603, pay attention to the temp gauge. They should stay under 95C in most driving, maybe up to 100C on a hot day, idling with the AC on. They should rarely if ever get to 105C (full load up a steep hill with the AC on or something), and it should cool down (under 100C) as soon as load is removed. Mine are very stable in the 90-95C range unless under load, but always drop right back.

HTH,

gsxr · #25 10-06-2003, 06:12 PM

Quote:

About the 3.0 liter six cylinder diesel engine in the later W126 cars - I know that most here on this site are concerned about cracked heads and overheating on this engine, but I've discussed this with the legendary Enrique at Mr. MB Motors in Southern California, and he swears that the newer engine is a better engine than the five cylinder, and doesn't have a high failure rate of cracked heads and overheating.

Paul, I agree with Enrique. The OM603 is a much better design in MANY ways over the OM617. Much more refined, quieter, less maintenance, more power, better MPG. But it just won't tolerate abuse and/or overheating like the OM61x, which was almost impossible to damage! Anyway, the 1986/87 six-cylinder 3.0L engines (OM603.96x) all came from the factory with cylinder heads that were weak - not strong enough in certain areas to withstand temporary hot running conditions. They will eventually crack. MB fixed this on later 3.0L engines (not shipped to the USA), as noted in the service manual, by making the castings thicker in some places. But all these USA 3.0L engines (86/87) ARE prone to cracking! I personally know of a good half-dozen or more, mine included. The fact that there were FIVE redesigns of this head (six part or casting numbers), and also FIVE redesigns of the head gasket (again, six total part numbers), shows that MB realized there was a problem with the original design back in 1986 and worked to perfect it as years went by.

The 1990-95 six-cylinder 3.5L engines (OM603.97x) all have a stronger version of the head, and these very rarely have head or gasket problems. However as you probably know, *all* those 3.5L engines had weak connecting rods, which oval out the cylinders, requiring a MUCH more expensive fix - which is NOT a DIY project like the head. Luckily, the 3.5L engines provide good used heads for the 3.0L! :p They're scarce and not cheap ($800-$1200 typically, used, with cam & lifters if you're lucky).

Now, the OM606 engine used from 1995-up in the USA does seem to be a much better engine, with no head or bottom end problems that I'm aware of. Perhaps that is what Enrique was referring to!?

On a side note, I have heard of very, VERY few OM61x heads cracking, or gaskets failing. Check this forum and you'll find lots of threads on OM603's cracking, but few if any 616, 617, 601, 602, or 606.

Regards,

Thomaspin · #26 10-06-2003, 06:12 PM

Thanks.

Do the fan clutches on the OM617 leak also?

I'm religious about cooling system maintenance and always use MB antifreeze, BTW. Really saw the benefits on the trip last week (2,500 miles in 5 days) where the engine would pull like the proverbial horse up steep mountain passes, while registering a modest increase in coolant temperature from 87C to 89C, a/c off.

Taking her up to 4,750 rpm (105 mph), with a little more on tap, on a level road, saw no increase in coolant temperature.

I'm on my third water pump (201k) and use one with the MB logo, preferring to believe tales of aftermarket pumps being less effective, although I have seen no compelling proof of this.

Come to think of it, I now have over 250k km during my ownership so I guess I'm eligible for the lapel pin. Got the grille badge with 153k miles on the odo (250k km).

gsxr · #27 10-06-2003, 06:25 PM

I honestly don't know much about the 617 clutches. I don't think they leak, they seem to be a different design. The 603 clutches are always wet after a few months, and they collect dust and grime all over the face. You clean it off, and it's back a few months later. I've never seen that on my 617 clutch. Also the 617 clutch is easy to check with the "roar" test, plus it stops instantly if you kill the engine with the clutch engaged on a hot day. Not so on the 603, never roars, and just stops slower - never seems to fully lock. At least with the newer 606 clutch (which both of mine have). Kinda odd, and makes it hard to test!!

On a related note, my 617.952 runs at incredibly steady temps - 85-90C almost all the time. Even in brutal summer heat, whether idling or climbing mountains, I can't get it over 95C. Very, very stable. To me that indicates an excess of cooling capacity with things in working order (I have recent radiator, clutch, t-stat, etc). The OM603, even when perfect, will run hotter. High speed runs using max power will drive the temps to 100-105C even on level ground with cool ambient temps. That's the price you pay for 20% more horsepower with basically no increase in radiator area (I'm assuming). It shouldn't run towards the red (110+) unless something is wrong though, and it should cool down within minutes after the load is removed. At least my 603's behave that way!

leathermang · #28 10-06-2003, 07:05 PM

They must leak... the instructions say they are supposed to be stored Vertically even at the parts store....

wildrose196812 · #29 10-06-2003, 10:57 PM

Sorry to interrupt the flow of info guys, but I'm fairly new at diesels, can anyone explain to me or point me in the right direction on how you determine the amount of timing chain stretch one has on his vehicle? Thanks...

wbain5280 · #30 10-07-2003, 12:07 AM

Quote:

Originally posted by gsxr

The 1990-95 six-cylinder 3.5L engines (OM603.97x) all have a stronger version of the head, and these very rarely have head or gasket problems. However as you probably know, *all* those 3.5L engines had weak connecting rods, which oval out the cylinders, requiring a MUCH more expensive fix - which is NOT a DIY project like the head. Luckily, the 3.5L engines provide good used heads for the 3.0L! :p They're scarce and not cheap ($800-$1200 typically, used, with cam & lifters if you're lucky).

Regards,

I'd still like to know what the newer and better engine number is for the 3.5L engines. OM603.97what?

There is one at work here, W126, a white one, and I just love the car.

Thanks