Turbo Failure/wear Verification - Page 2 - PeachParts Mercedes-Benz Forum

DslBnz · #16 09-03-2003, 07:43 AM

UPDATE

350 might just be fine. After disconecting the EGR, the car ran like a clock. Because of the EGR, it was shaking violently.

The oil consumption has stopped. I left it down a qt 130 miles ago. Looks like valve seals after all.

Phew, that's a load off my back! How many 350 stories end like this?

:p

gsxr · #17 09-03-2003, 12:11 PM

Glad to hear you may have solved the problem. Oh, and glad to see you made it over here, Marshall!

#18 09-03-2003, 12:40 PM

If you are using oil at the rate you report, you have engine problems.

Best information I have is that there were more than 15,000 W140 cars with OM603.97 engines made/sold worldwide and many/most seemed came to the US or went to Japan. There were about 3000 W126 cars with the 603.97 engine by my count. That's approaching 20,000 engines - there were some used in G-wagons too, but I have NO numbers for them. Mercedes has acknowledged that the engine failures were confined largely to US cars (but they have NOT ever actually acknowledged that there is an engine problem with the OM603.97 engine). I have communicated with about 100 owners of cars with these engines. More than half of them have had replacement engines installed. Most were replaced before the engines reached 100kmi and more than 90% of the replacements occuring before 150kmi. I know of owners with 200-300+kmi on the original engine and NO evidence of any malfuntion. I know of two replacement engines (I've included yours) that seem to have failed the same way that the original engines did. I know of one that was destroyed by serious abuse - and I just won't count that. This is a very much lower failure rate than the original engines exhibited (this is NOT a sample that can be considered as being representative, but seems pretty representiative of the MB owners that I know). By 5 years of age the original engines were failing at a high rate. After more than 5 years, the rate of failure of the replacement engines is MUCH lower.

The highest percentage of failed engines that I've seen were in cars that were used largely (50+%) or almost exclusively for city driving. Cars that are used almost exclusively for highway driving seem to have a far far lower failure rate. The reports of failures of original engines has dropped dramatically in the last few years despite almost half the original engines still being in service and most of them having well over 100kmi on them with some having 200-300+kmi. I hadn't gotten a report of one in more than 6 months until I heard of yours. A few years ago I was getting more than a report a month. Oil consumption on these "good" engines (as well as replacment engines) is just about what other OM60x engines display - maybe a qt every 5-7kmi.

More than half of the original OM603.97 engines THAT I KNOW OF that are still running today, use Mobil synthetic oil (either Mobil 1 or Mobil Delvac 1) with a few more using Amsoil synthetic (base stock supplied by Mobil but a different additive package). I do not have any proof that the oil makes any difference, but I have a BIG preference for it based on my own measures of engine wear, improved cold weather starting and lifter noise. Oil sure can't reverse wear or damage that has already occured or damage caused by trying to compress something that is incompressible, but it can reduce wear dramatically at cold start (much less friction) and timing chain wear rates on all of my OM60x engines dropped by more than 50% when they were switched to Mobil synthetics and even when running (fuel economy improves measurably, but by only a few percent in my experience) when conventional oil is replaced by synthetic).

Marshall

DslBnz · #19 09-03-2003, 03:34 PM

Marshall,

You said you've seen many 350 original engines with 200 - 300K miles on them, still running well. I have seen a 1995 with 225K miles on ebay that had an oil burning problem;

The engine failure will happen, it's just a coin-toss as to when.

You said the failure rate for the past five years on rebuilt 350 engines was much lower than when the original engines were in the cars. Maybe the connecting rods last longer in the newer ones, but still cannot hold up to the pressure over time. My 350 has had 2,500 - 3,000 mile regular dyno oil changes and was always highway driven.

I need to find a 350 with the rebuilt engine, that has over 400K miles. As far as I'm concerned, if it can't hit 400K miles, it's not tough enough for me. As of right now, I know of none that have that many miles. Time will tell, I guess.

gsxr · #20 09-03-2003, 04:05 PM

The new connecting rods are MUCH stronger. To date, I have not heard of any of the new rods bending. I believe it was simply a weak design on the old rods, and the new ones should last indefinitely.

I know one old mechanic who ran his German auto repair shop for decades. He's a friend of my family from way back. I asked him about the infamous 3.5L grenades. He said he'd buy one in a heartbeat if it had no symptoms, then promptly tear the engine apart and install six new/updated rods. On an engine with no symptoms of failure. He also firmly believed the problem was the old/weak rods, and replacing them BEFORE they failed/bent was good preventive maintenance. YMMV, as usual... and for the record I still prefer the good ol' OM603.96x, 3.0L...

DslBnz · #21 09-03-2003, 04:29 PM

--
gsxr

Yes they are stronger. So they should last indefinitely?

Out of curiousity, does MB still sell the engines with stronger connecting rods?

--

Marshall,

The 350 does burn about 1 qt in 500 - 600 miles when the oil is topped up. When it is down one qt, the oil consumption practically stops. If it was engine trouble, wouldn't it keep consuming oil regardless of the oil-level?

gsxr · #22 09-03-2003, 05:23 PM

MB doesn't sell any OM603's with the old/bad rods anymore. All you can buy new are the "good" rods.

As to the oil consumption, I'll let Marshall explain to you in detail how those dipstick marks are not "Full" and "Add", they are "Max" and "Min" - two very different meanings that most people misinterpret. (It's one of his favorite subjects!)

Point to ponder: Have you ever considered just letting it go until it reaches the "Min" mark?

DslBnz · #23 09-03-2003, 05:29 PM

Quote:

Originally posted by gsxr
Have you ever considered just letting it go until it reaches the "Min" mark?

In the process,:p

I assume the oil light will flash intermittently. So I will keep that in mind.

gsxr · #24 09-03-2003, 05:42 PM

The oil level light is supposed to be on a 60-second delay. If it's coming on during left turns when low, the delay circuit is bad. This is becoming more common on the older cars. You can ignore it as long as the level is above "Min". Fixing the delay requires replacement of the oil/temp/fuel gauge pod which isn't cheap ($250+).

DslBnz · #25 09-03-2003, 05:47 PM

My sister's '87 300D has that problem. Oil level was full.

However my sister was panicking in the car that it was going to break down and die, or maybe she'd ruin the engine. EVEN AFTER I checked it, and I told her it was FINE.

gsxr · #26 09-03-2003, 05:50 PM

Unplugging the wire to the sensor on the side of the oil pan will keep it off permanently...

#27 09-03-2003, 06:38 PM

In April 1991 Mercedes sent out TSB 00/86a

It reduced the recommended MAX oil fill amount of ALL 601/602/603 engines sold in the US by 0.5 liter. This revised level is about 25% below the MAX mark on the dipstick!

Then in 1995 they sent out TSB 00/57A. In it, they cautioned that owners should NOT top up the oil frequently. They point out that there should NEVER be sufficient oil in the engine so the level ever reached above the MAX or FULL mark EVER. They point out that the optimal level is midway between the top and bottom marks, and that there is NO advantage to adding oil before it reaches the ADD or MIN mark and owner "...should refrain from frequently "topping off" the engine oil level."

I have owned/driven 22 different Mercedes cars for more than a total of a million miles and EVERY one (gas or diesel) would exhibit increased to excessive oil consumption if driven at highway speeds with the oil at or near the MAX level. Drop the oil content of the engine to a level about midway bewteen MAX and MIN and the oil consumption would usually be reduced a lot.

If you happen to use full synthetic oil (especially Mobil synthetics) the oil level registered on the dip stick will under report the oil content of the engine from anywhere from a pt to a qt unless the engine has been shut down and the oil allowed to drain back into the pan - for HOURS. With the Mobil syhthetics that I use, this takes between 6-8 hours! If you top up a recently shut down engine with Mobil 1 15W50 oil to the MAX mark, the engine will be overfilled by at least a qt and oil consumption will be high! I suggest that you check the oil in the AM before starting the car the first time that day. On OM60x engines (and late OM617.95 engines made after 4/84) the distance between the two marks is 2 liters (2.15 qt). If the level is above the MIN mark add a qt. When checking the engine on the road, if the level is below the MIN mark add no more than ONE qt. That's plenty as long as it brings the level up to the MIN mark. Check it the next day after it sits overnight and see where it is. It will usually indicate engine oil content between a pint and a quart above where it was before fully draining. If you engines behave like mine, there will be PLENTY of oil in the engine. I've been trying for several years to estimate what the actual oil content would be when the dip stick reading was MIN or midway at say 5 minutes, or 15 minutes or a couple of hours after shutdown, but the results are NOT consistant. This measuring issue is NOT a serious problem with conventional oils or with MANY/MOST so called "synthetic" oils that have a high hydrocracked oil content.

Marshall

kashbaugh · #28 09-04-2003, 07:59 AM

Marshall,

You seem to be really sold on Mobil synthetic oil. I just bought an '85 300 TD with 231k and want to "do it right". I intend to drive it about 400 highway miles a day - I'm a courier sometimes - and would like to know "the short answer" on why you like the synthetic so well.

Also, with that kind of milage how often should I change a synthetic? And what exactly would you recommend? Is it just "Mobil 1" or is there more to look for on the label?

Sorry to ask such lame questions, but I'm trying to "get some larnin'" on these things.

kma

gsxr · #29 09-04-2003, 11:07 AM

kma,

I'm not Marshall but I'll toss my two cents in for free:

There are numerous advantages to synthetics. Among them are better cold flow which reduces wear at cold starts, much improved winter starting in cold climates, better fuel economy, cooler oil and therefore engine operating temps, much better performance under extreme conditions (such as turbocharged engines), and the ability to extend the drain intervals to save money (and help the environment a little as well).

You change the oil when it's worn out. An oil analysis or two can give you the data you need to determine the maximum change interval, which is usually (but not always) limited by the soot level. Mobil-1 can suspend about 2% soot. On my 617 engines (like yours), that typically translates into 7500-10kmi. My newer 603 engines could go 15k-25kmi since the OA on those shows less soot than my 617 makes, but I change then at 10-15k anyway. Delvac-1 (which is a super-duty diesel version of Mobil-1) can suspend about 3-4% soot, allowing even longer intervals. Anyway for mostly highway driving, I'd say 7500-10k is probably safe, I wouldn't go beyond that without some OA to back it up. Or, maybe 10-12.5k on Delvac-1, again without OA. Changing at 5k with synthetic is, IMO, wasting money and pouring out perfectly good oil (and yes, there are people who do this).

The ONLY version of Mobil-1 that I would use is the 15W-50 weight, with the red cap. All of the xW-30 weights are too thin and NOT approved by Mercedes. the 0W-40 (black cap) is approved but it really is not needed unless you live at the North or South Pole. The 15W-50 has almost the same cold pourability, something like -50F! Best price is for the 5-quart jugs at Wal-Mart at ~$19, but the 15W-50 is not always available in the 5qt size for some reason (it has shown up at my local Wal-Mart recently though, which is nice.)

For the record, I use Delvac-1 but this stuff is HARD to find, you either need to mail order it, or buy from a local Mobil distributor. It also costs more - ~$21/gallon or higher. Amsoil is a good alternative. Avoid any Castrol, Shell/Rotella, or Chevron "synthetics" which are really just processed dino oils, not true synthetics, and aren't suitable (IMO) for extended drains. Whew. Wonder what Marshall will add.

#30 09-04-2003, 03:21 PM

My preferance for Mobil synthetics is based on LOTS of personal experience and discussion with both Mobil tribologists and other lubrication specialists. The product they make does what I want the oil in my cars to do. It does not cost me much more than using very much inferior products (Mobil synthetic can USUALLY be changed less often then conventional oil, but that depends on operating conditions and requires oil analysis to establish). Mobil has usualy been forthcoming with information about the the suitability of products they make and they have NOT insited that the most expensive product was the most suitable product. There are many things the oil must do and maximizing what the engine can do while minimizing the wear and cost is something at which Mobil synthetics excel. There are oils that come close and some of those cost less so under some circumstances they MIGHT have a small economic advantage, but most of those oils have at least some disadvantage and some of the disadvantages are critical to me so make thir use unacceptable. There are also oils that cost more, but I can find NO evidence that the more expensive oils provide ANY benifit in MB engines.

There are many other oils mass marketed as synthetics, but none of them compete favorably with Mobil 1 in my opinion. I'm sure there are marketing people at Shell, Castrol, Valvoline, etc. that disagree. When discussing the subject with independent experts however, none have take exception to my belief that Mobil really makes an exceptional product and it's a bargain!

Marshall