A couple of months back I purchased a 1993 300SD/W140 style. I bought it despite reading alot of comments about engine and air conditioner woes. Bent rods, excessive oil consumption, evaporators leaking, etc., etc.

Against my better judgement, I went ahead with the purchase anyway, trading my venerable 1984 300D Turbo... rusty but reliable.

I sent the 300SD into my local shop to get some things done to it, primarily replace the glowplugs, get some things checked out, etc. I got it back, and I still didn't like the way it sounded and it was still using too much oil. It also sounded like the timing chain had commenced to slapping. So I sent it back in. I had the top end checked out. Seems the head gasket was leaking on #1 cylinder. Injectors were bad on a couple of cylinders. They pulled the head, had 1/10,000 shaved, new injectors, new timing chain, etc. They checked the piston travel and they were to spec. No bent rods....... whew!

I picked it up and after driving it that day about 145 miles, it sounded like a valve was going to pop through the head! It was so loud it was embarrassing and it smoked like crazy... especially at night when the headlights of a vehicle behind highlighted the exhaust.

So back to the shop it went.

The shop didn't replace the hydraulic lifters. So they replaced them for the cost of the parts only. Still a major job....It now runs fantastic... does not burn oil, is unbelievably quiet, and it absolutely will fly..... I cannot believe the acceleration especially compared to my 300D. I have now put about 2,000 miles on it post repair and it is just great. I love it. I know these are much maligned engines and cars. And I was about to go trade this one if I could just get it back together and running. But not now. Not yet anyway!!

The head mechanic at the shop I took it too said that bad glow plugs are the primary culprit of bent rods... that the combustion chambers being so small that if the fuel is injected in too high a quantity/not atomized or the glow plugs are not functioning, it can cause enough liquid to be in the top end that will not compress.....causing bent rods or blown head gasket.

I'm going to give my vehicle a chance now that I've gone this far with it. I am optimistic at this juncture that the previous owner may have thought they had a lemon and I am hoping to have turned it to lemonade.

Any other W140 owners out there to share their experiences?

JMH

This does not sound plausible. If there was too much fuel being injected and the cylinder did not fire, the excess liquid, if it existed as a liquid, would simply stop the engine from rotating. It does not take too much to stop the engine when it is turning at 200 rpm. The forces involved in this stoppage are not high enough to bend the connecting rod.

I also have serious doubts that you could inject enough fuel to have sufficient liquid collect in the cylinder (more than 25 cc.) to cause the engine to stop rotation. The fuel does not accumulate in the cylinder. Every time the exhaust valve opens, some of the fuel charge is forced into the exhaust.

Wasn't there an hypothesis posted about a year ago, perhaps by the dieseling doctor, that the head gasket was failing between an oil gallery and the 1st cylinder causing oil to enter the cylinder and resulting in a bent rod by the method mentioned?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I am only the messenger! I would think that the exhaust valve would release the liquified diesel into the exhaust manifold too, however, the problem is on the compression stroke. If enough of the liquified fuel charge accumulates, the net effect is a washing down of the cylinder walls, residual fuel remains and with each rotation it increases the possibility of the "liquid not compressible" law of physics. Perhaps the head gasket would go first, perhaps the electric starter motor would stop but maybe, just maybe if it hapens enough times, metal fatigue might result and the rod might develop a slight bend. Just a theory based upon what the head mechanic said. The head mechanic I refer to has done many a repair job for me on Volvo's and Mercedes vehicles and has always performed admirably. He has 3 Mercedes with the 603.971 engines and he swears by them as long as they are maintained. The first question he asked me after I bought the car was if the glow plugs were 100% functional. While his statement on the glowplugs and/or bad injector nozzles as the possible culprit/cause of bent rods may or may not be accurate, far be it from me to tell him he's wrong when he has thousands and thousands of miles on his 603 engined cars (3 of them).... and never had a bent rod or needed an engine replaced... and yet that much maligned engine has been vilified on this website as unreliable, poorly engineered, a sign of the downfall of Mercedes quality & engineering, etc., etc.

Maybe he is at least partially right. The miles he has on his cars speaks for something...

JMH

Perhaps. And perhaps that fact the Mercedes designed beefier rods for the engine also speaks for something. If it were truly just glow plugs it seems to me that Mercedes could have saved a great deal of money and customer good will by designing longer lasting ones and replacing the originals via a recall or similar campaign. The replacement parts for the 603.97x suggest that Mercedes knew there was a problem with the rods. Still, the 140 SD's are wonderful to drive when they're right, and I hope yours gives you hundred thousands of trouble free miles. I have a secret fantasy where I get a pristine 140 with a blown engine, and drop a 606 turbo into it. Apparently these were sold in Europe, but never made it here.

__________________
Tjohn

82 300 SD
77 450 SL (gone)

Thanks tjohn... I too hope to get thousands of miles out of this rascal. It is my daily driver/work vehicle. I have put about 2,000 miles on it in the last 3 weeks which would be typical driving for me so I need reliable. The nice thing is I get a mileage stipend so having a reliable car that I own free & clear is a bonus..... and sure helps the slush fund.......

Who knows the answer to all of these mysteries but if Mercedes beefed up the rods, it would point to an acknowledged problem for which they were culpable....

Best Regards,
JMH