So tell me, will a comp. test catch a bent rod in a 140? - PeachParts Mercedes-Benz Forum

muleears · #1 11-24-2006, 12:05 PM

I've searched and I know as the rod bends the cylinder gets out of shape. I assume this causes a loss of compression.

I am in the market for a 140 and may not have the opportunity to drive it a few hundred miles to check oil consumption before I make my purchase decision.

Won't a compression test reveal if the #1 cylinder (or others) are out of spec. and thus have a bad rod?

In my searching I have learned to look for a smooth idle, little blow-by and low/no oil consumption, oil in water, water in oil and quick starting as engine condition indicators. Is there anything else to look for that would indicate a bent rod?

TheDon · #2 11-24-2006, 12:10 PM

ok.. if its the OM603.970 . the earlier ones were problamatic.. the later ones were not as IIRC ... but get a compression test to see what the compression looks like.. only a visual inspection will tell you the condiditon of the cylinder walls

i just noticed this was the first model year to change the name nomeclature from 350SDL... to S350 Turbodiesel with the I6

#3 11-24-2006, 01:28 PM

Unfortunately, I'd recommend you look for a gasser 140 (S320). It's a crapshoot if the engine is on it's way out or not no matter what. The W140 300SD and 350SD should be avoided unless you like taking a risk.

sixto · #4 11-24-2006, 03:20 PM

My SD with two bent rods idled nicely. I don't have the right adapter for canted injector prechambers so I couldn't do a compression test. I've read the engine can have bent rods and still hold compression to within 10% of a neighboring cylinder. Probably because of the carbon build-up when the rod bends.

In short, there's no way to know without pulling the head. The manual talks of sending a dial gauge through the prechamber hole but that would add 10 hours labor to a PPI.

Either get a 95 S350 with chassis serial number 260000 or higher, or a July 95 or later build date.

As FI said, you will pay a lot less for an S320 (or 420 or 500) in comparable condition and have money left over for years of paying the difference in fuel costs.

For what late 95 S350's go for, you can also get a 98-99 E300.

Sixto
93 300SD

Hatterasguy · #5 11-24-2006, 04:28 PM

No the engine will run in a perfectly fine manner until the rod is really bent and you are burning almost as much crank oil as fuel oil!

Compression test no as well.

Buy a gas one.

muleears · #6 11-25-2006, 05:43 AM

Does the bending of the rod happen over time (several thousand miles) or is it a one time 'event'? IOW does the car slowly begin to burn oil or is it a dramatic change?

muleears · #7 11-25-2006, 07:18 AM

I agree with the advice you all have given me. I think the W140 is just too much of a gamble

. I think my best bet is a W210 of the mid/late 90's vintage. I'd really like the turbo with the 5spd. auto, but I'd have to have a '98 or newer. Don't know if the pocketbook can stand it

. Anyway, thanks for the great advice, you have brought me to my senses

.

Hatterasguy · #8 11-25-2006, 05:44 PM

My friends dads S600, and my friends S320 have been dead nuts reliable. W140 is a fine car.

My other friends 98 E300D has needed more work last year than the S320.