350 SDL Fuel Injector Replacement & Rough Idle? - Page 2 - PeachParts Mercedes-Benz Forum

unkl300d · #16 03-28-2003, 12:35 AM

Well, I looked at the car.
I chatted with the seller's friend, the mechanic who owns the shop. Some young guy who is into mustangs personally.
Anyway the car is white with grey leather interior.
Has a slight dent under the right rear light.
Body looks good as does paint. Rims so so, interior is fair. The rear seat has a deep scratch and some buckling in rear seat pads.
126K miles. What a waste !!!!!

This car looks like my W126 300SE except for ext. color.

The mechanic was airly forthright. He said that it smokes like crazy. It fills the street on a short drive.
He started it up and it has a break on a down pipe part of exhaust, so ehaust smoke rises from engine compartment.
It started right up. No harsh noises except for the glass pack sound of the exhaust leak. I had him turn it off after 4 minutes.

He told me that ndependent diesel mechanics would not touch it and that the dealer quoted a price for a new motor.

Basically, that car is history unless a mechanic buys it for dirt cheap.
Since it does run, he would be better off giving it to a charity for tax deduction.
What a waste!!!
Nice car. Terrible waste

stephenson · #17 03-28-2003, 07:51 AM

Way too bad ... same color combo as mine ... my paint is extraordinary for a 13 year old car ... the 126s hold up so well with just a modicum of care ... particular shame about the leather ... very expensive to replace ... tough to repair well enough.

Am just amazed at how folks would allow cars to devolve to that level ...

On the other hand, if you could buy it for $500 you could likely make some money parting it out ...

Sad.

ezrider · #18 03-28-2003, 10:09 AM

update (I started this thread). My rough idle and injector knock condition was cured with $8.00 worth of parts. The injector pump pressure valve copper seals and O rings were replaced again by a more competent mechanic, problem solved.

I am the original owner of this 1991 350 SDL, it just turned over 150K miles. It has been a wonderful car. It uses a quart of oil every 1500-2000 miles, other than that there are no issues with the motor. There is a leak from the fronk crankcase seal so I can't tell how much I'm actually burning.

The serpentine belt tensioner shock has to be replaced every year or so, there is a bushing in one end that fails, strange that MB won't put a stronger bushing in it.

I was getting a moderate overheating condition and recently replaced the radiator and water pump, problem solved.

I tow a heavy closed motorcycle trailer with this car at 80+ MPH speeds from time to time, no problem mon......

stephenson · #19 03-28-2003, 10:22 AM

hey ezr,

Getting ready to replace damper (shock) again ... this time am gonna replace the idler pulley, as well. Maybe this will help it last longer.

Previous failures (about every 18 months) have occurred with sounds of severe vibration, but this time it sounds as if it someone is "tapping" on an aluminum shaft ... kind of a "tick" "tick" ... on occasionally, and only at idle.

While my oil usage used to be very tiny during a 4000 mile change interval, since I switched to Rotella Synthetic from Mobil 1, it seems to have increased a bit ... maybe 1/2 quart per 4000 miles.

Just found a hi-Cetane station and am trying some $1.98/gallon stuff to see if anything is different ... I think I do have less smoke on start up ... and very limited smoking on hard acceleration.

gsxr · #20 03-28-2003, 11:03 AM

About the serp belt shock failing often. I've been told that the aftermarket parts simply don't last as long, and that the rear genuine Mercedes part is much more robust (and a LOT more expensive, more like $75 instead of $25). Next time mine fails, I'm going to try it. If you guys are already using OE parts and they're still failing, please let me know and I won't bother. I think there's a 12 month warranty on dealer parts, so check it closely at 11.5 months!

stephenson · #21 03-28-2003, 11:09 AM

Have used OE last two times (not from local dealer, but through FastLane connection to dealer network).

Did not see much difference ... fails just outside the 12 month window.

gsxr · #22 03-28-2003, 11:20 AM

What part number did you get? The latest is a 604- number, the older style is a 601- number. The 604- is much more expensive than the 601-. Also, do your parts arrive FedEx direct from Mercedes...? Just curious.

stephenson · #23 03-28-2003, 11:37 AM

Called better half at home ... still in box and bag:

damper is 604 200-01-14
tensioner lever is 601 200-17-73

I think the damper was in the $25-30 range ... forgot to ask her that.

gsxr · #24 03-28-2003, 11:58 AM

It's the 604-200-02-14 that costs twice as much, and supercedes the 01-14 on some models only (which is REALLY weird). On my OM603.960 the 02-14 is the latest part number.

Chris p · #25 03-31-2003, 01:17 PM

I own a 91 350 sdl and it has 183,000 miles on it and it runs great and I have had no problems with it. I was really scared by the postings about this engine after purchasing it 3 years ago. This has been a very reliable strong running engine. I would purchase another in a heartbeat. It delivers 25 mpg at 90 mph with the ac on. I am sure you could also find people who have had gas engines fail earlier that they would like also. you must look at every car individually not lump all of the 350 engines together.

gsxr · #26 03-31-2003, 01:38 PM

Sorry, Chris, but there really was a design flaw with the original connecting rods on all OM603.97x engines. Mercedes wouldn't have re-designed them and quit selling the old rods if they were OK. Not all of the 3.5L engines have failed of course, and not all necessarily WILL fail. The point is that there is a MUCH higher probability than normal for this engine to have a serious bottom end problem. The car itself is great, as you mention, and as long as you're willing to accept the fact you may need a $4-8k rebuild/repair at some point in the future, you have nothing to worry about.

stephenson · #27 03-31-2003, 01:56 PM

Chris,

While I would likely agree with you in most cases, the facts on the the 3.5L do bear out the hysteria heard in many places ... they appear to have an extraordinarily high failure rate - not all, but many do fail. There appears to be no "like occurence" in the world of MB events ... sounds like you and I and few others got lucky.

Now, perhaps there is a common issue that initiated the failures on the ones that did ... the only pseudo-technical issue I have turned up is the incredible amounts of gunk in the intake system created (I think) by the interaction of the EGR and the crankcase fumes (from the valce cover) ... mine was absolutely awful ... and, I had, prior to cleaning it, several instances where the engine would, at high speeds) pause momentarily and emit a very dense, brown puff (not normal diesel exhaust) of exhaust and then return to normal operation. My thought is that the intake was dragging in indigestable chunks of this stuff and that may have been what damage those large percentage of engines that did fail. I would assume the failures would be, based on logic, more prevalent in high heat areas and in town, low rpm driving.

Chris p · #28 03-31-2003, 02:11 PM

I think that you are right about the intake manifold and that crud being the possible cause of the engine trouble. I have had my manifold off and cleaned it as it was very filthy. If a chunk did break off and was sucked into the engine it could do the damage that is referred to in the posts about bent rods and engine failure.

gsxr · #29 03-31-2003, 02:17 PM

I hate to be the consistent stick in the mud

but the intake crud is not likely to be the problem. Why? Because that problem exists on all OM60x turbo engines and it has not caused ANY bottom end failures on the smaller 2.5L or 3.0L versions. My intake was also fully gummed up with a thick layer or carbon. The EGR system is evil and should be positively sealed off, as long as your car allows this (on 1990-up 2.5L turbos this can't be done easily, as it screws up the engine computer and the engine won't run properly).

Here are some photos of my 3.0L OM603.960 intake gummed up pre-EGR removal, and also my EGR block off solution (my engine has no computer controls other than idle speed):

http://www.meimann.com/images/mercedes/OM603_intake/pipe_before.jpg
http://www.meimann.com/images/mercedes/OM603_intake/pipe_after.jpg
http://www.meimann.com/images/mercedes/OM603_intake/EGR_removed.jpg

Regards,

stephenson · #30 03-31-2003, 02:33 PM

gsxr,

Agree that crud cannot be sole cause ... MB obviously changed the rods, ergo, they think stronger rods prevent the end state. Question is, is the bending phenom related to the rods alone in normal operation, or is there a non-linear event that occurs ...? We have heard various opinions ... water in fuel, coked oil deposits, etc ... is the EGR in the same place as the rest of the engines you mention ... seems like the location of the hot gases entering relative to the position of the oil fumes might be significant?

BTW, my intake was even worse ... terrible looking. Was dipped at a machine shop about 10 times and then I spent hours dragging solvent rags through the intake manifold and pipes.

Nice job on the block off ... was it difficult to get the exhaust manifold sealed up with the round aluminum piece and then clamped? (plate was pretty straightforward, right?)