The 200D and 240D were underpowered for sure but the engine was substantially over engineered and the output extracted was well within its tolerances, nothing was being pushed, as I said in my previous posts, the 616 when pushed to 72bhp with raised RPM began to bend rods on vehicles which were not being maintained to 100%, the same engine with abuse and almost 30% maintenance would last up to 400,000 miles with ease.

__________________
99 Gurkha with OM616 IDI turbo

2015 Gurkha with OM616 DI turbo

2014 Rexton W with OM612 VGT

The OM616.x and OM603.971 used the 92.40mm stroke. The OM616.x rod failures were associated with substandard maintainence. It is likely the failed OM603.971 engines were lightly driven and/or not maintained to fleet specifications. These conditions lead to erratic behavior of the diesel engine when starting and probably when stopping.

Really, I think Mercedes engineers are and were perfectly capable of designing a diesel engine with rods strong enough for a 400,000 to 500,000 mile lifespan. Voila, they do last that long in fleet vehicles.

If the vibration/timing were just a little off that would increase loads on the rods enormously in a stroker engine. Going from 84mm to 92.40mm is a huge increase. Going from 88.30mm to 92.40mm is also a big increase. Look into rod failures in high performance stroker engines -- with premium rods. If the timing is off -- it's all over, folks.

There is one thing you cannot really model even with a super computer and that is the effect of negligent maintenance.

These failures are associated with one rod (correct me If I understood that wrongly). That is not a rod design issue. It is a system issue. The same destructive behavior is seen on the tensioners. The loading on the belts from erractic engine behavior is hugely increased.

In the other thread the pictures show #6 piston skirt has similar wear pattern as #1.

There is indication dealer maintained cars were subject to bent rods. This is not a qualification of dealers, rather a suggestion that 603.97s that bent rods received the same care as 603.96s that didn't. My money's still on a design flaw... partially, if not completely.

Sixto
87 300D

Number 6 would be in line with number 1 as far as vibrations go. My thought was that the flywheel and torque converter act as a defacto damper. This seems to be the case if it is a race against which one will fail first.

Is there a correlation between failure rates and the climate? The prediction would be a higher failure rate in colder climates. If a block heater was not used this would likely obviate dealer maintainence. Are block heaters in general use in fleet vehicles in cold climates?

Ah, but if the rods were irrelevant, the new/updated rods would still be bending. And they are not, or at least are so rare that few if any have ever been reported. What is interesting is that the bending mostly occurs at #1 and #6 cylinders. 'Tis a shame the problem exists at all, us power junkies would love a little more displacement. If I could get an 0.030-over 3.5L then I could badge my car "E36", lol...

__________________
Check out my website photos, documents, and movies!

Anybody verify that the replacement engines have these length rods? Or even this actual displacement?

I just converted my 93 300sd to Elsbett SVO/WVO system. When I rebuilt the injectors, the injector nozzles at the front and back of the engine (1&6) would not come out. The others fell out on disassembly of the injector body. Soaked in brake parts cleaner and then came out with some tapping. They were stuck because of black deposits/gunk between nozzle body and injector body. I was also amazed to see the amount of black oily sludge in the crossover pipe, etc. 1/8 inch, some of it hard. I am guessing some of this is coming through pcv valve. Don't know if that is typical or what with these engines?

Yep, the crud in the intake is normal, thanks to the EGR soot mixing with the PCV vapors. Don't spend too much time cleaning it out, it will just come back, but scrape off the major deposits before re-installing.

The only way to eliminate the buildup is to disable the EGR. But this isn't easy... it requires either fooling the computer into thinking the EGR is still working, or converting to a pressure-operated turbo wastegate instead of the computer-controlled, vacuum-operated, reverse-Polish wastegate that is used on your 603.971 engine.

Doing a little research before wrenching, I ran across a couple of interesting things in the FSM:

On the 603 engine, it is mentioned (PR 01.1014/4), in a repair for complained coolant use, that the head gasket can fail. When the gasket has failed into the combustion chamber, it is mentioned that the piston protrusion should be checked, "Possible initial damage to conrod as a result of water hammer.".

It only affects the 124 in this repair, but does IMO support the possibility of hydrolock damage to the conrod due to coolant or oil in the combustion chamber.

__________________

Gone to the dark side

- Jeff

Excellent point -- if you aren't an experienced diesel tech (I am not) you might not think to check for conrod damage from a simple bad head gasket.

this is an excellent point HMX. especially in an inline motor. perhaps MB decided that the piston design couldn't be altered and maintain integrity, so they shortened the rod instead. insufficient R/S ratio could load the side of the skirt as well. HMMMMM

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

It seems to me fairly obvious: this engine should not have been bored nor stroked.

The additional bore eliminated the water-jacket between the bores: not good.

The additional stroke caused the wrist-pin to be moved lower on the piston and the rods to be shortened for clearance issues: not good.

It makes sense to try and develop more power and at lower RPM, especially in an IDI diesel, for emissions and fuel-efficiency reasons. However, this really required a new block, as modifying the 603 took away its reliability and longevity.

They're probably quite happy that this engine was a North American engine only, saved them some embarassment in the rest of the world.

I do have a couple of headless 603s in my shop, the 3.5L is for sale cheap if someone needs a useable engine or even a rebuildable core, ... Anyway, the point is that the 3.0L engine has 256,000miles, and you can see all of the crosshatching in the bores. Beautiful. The 3.5L has 237,000miles, and there are scuffs in all cylinders, not as beautiful. Both were good running engines, but you can see that the 3.5L is not going to last as long as the 3.0, just because there will be more cylinder wear. At least, the 3.5L will be expected to use more oil through its mature mileage.

What Mercedes-Benz Engineers needed to do since Marketing runs the show there, is unknown to us at this point. Most of us would like to have the 603.96x continue with the re-designed head, and adding an aftercooler, a multi-valve head, ... VGT, ... a 606? The 3.5L can be a good engine, but IMO never as durable as the 3.0L.

__________________

Gone to the dark side

- Jeff

Pal of mine who posts here from time to time has about 425k on his 3.0L, head was off about 18 months ago for gasket and crack repair. Other wise has low oil consumption for what it is... 1 quart in around 1500 miles. I've only seen a few HIGH mile Diesel vehicles. 350K and greater, most have clapped out interiors, bad front ends, trans fails, no AC, etc... and that's how they meet their maker.



Nevertheless, have you measured the compression height (wrist pin location) between the 3.0L and the 3.5L? Disregard the diameter of the piston for this. Then we can make a better assessment of what was done to the bottom end I'd imagine once we have all measurements. Maybe the piston was redesigned, maybe not. Doesn't sound like it.

I'm not that great with math so some of you other guys will have to figure that part out... and leave the excessive beer consumption to me for ideas.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

There are lots of this engines (603.971) in Europe, too.
And it is strange, but they don't seem to bend rods like the ones in America...
I have one with 214000 miles and the engine is still very good.

In my opinion the damage occurs during chaotic running. The 3.0 liter version of the engine shows the damage by the frequent failures of the serpentine belt tensioner. There is a huge amount of stress on engine components during this behavior. The number one and number six cylinders would be most damaged -- the flywheel/clutch/torque-converter acts as a de-facto damper at one end leaving the number one cylinder to absorb the shocks. Over time this can easily lead to rod bending.

People, do some research on how sensitive stroker motors, in particular the rods (because of the angles involved), are to damage from misfiring. There is a huge data set out there from motors that illustrate this damage and those that do not.

People want to blame Mercedes engineers for this. I don't think that is fair at all. The engineers must assume the owner maintains the engine properly and that includes the responsibility for assuring that it starts and stops quickly. There is no way for them to anticipate the "ingenious" methods of abuse.