connecting rod bearings look worn - PeachParts Mercedes-Benz Forum

petecooke · #1 12-03-2011, 06:06 PM

I am replacing the rings on my 1983 240d.
The bearing on #2 and #3(haven't done #1 or #4 yet) look a bit worn. I've attached photos. There's about 200k miles on the motor.

If I replace the connecting rod bearings, do I need to have the crank ground at a machine shop?

Any thoughts?

Thx

pete

kerry · #2 12-03-2011, 06:08 PM

You're right, those don't look good. I think it depends on the condition of the crankshaft. From the appearance of those bearings I'd venture the engine had been run out of oil or something.

layback40 · #3 12-03-2011, 06:11 PM

Quote:

Originally Posted by kerry

You're right, those don't look good. I think it depends on the condition of the crankshaft. From the appearance of those bearings I'd venture the engine had been run out of oil or something.

X2 on low oil.
Best check main bearings as well.
Is the oil pump good?
What did it run like before the motor was pulled down?

engatwork · #4 12-03-2011, 06:38 PM

Are there any visual indications on the crank? If there are you are going to want to get it to a machine shop for check out.

47dodge · #5 12-03-2011, 07:34 PM

Measure the crank to see if it is round, and within spec. Also does it mirror the wear on the bearings if so then it will likely need to be polished or ground. If it is smooth and within spec you are fine. Run your finger nail across it, should not catch or feel bumpy.

t walgamuth · #6 12-03-2011, 07:35 PM

At two hundred thousand miles the bottom end if well cared for is like new on these engines.

As the other fellows said it looks to have been run low or without oil.

And that said you will need to go completely through it as there will be bearing trash in all passages and worn parts such as cam cam chain and oil pump.

Sorry.

47dodge · #7 12-03-2011, 07:58 PM

I am sort thinking this engine may really need to have a real good look at it. Broken piston unknown cause(broken valve but why?), bad bearings. Seems the list of ills is getting bigger. Is the engine out of the car? A complete tear down may well be in order to truly assess it condition.

vstech · #8 12-03-2011, 08:04 PM

while those bearings certainly do not look good, I have seen MUCH worse.
they look like a car that went WAY too long on the oil, or one that has had coolant in it. I do not think it was run out of oil before.
look at the bearing thickness, it's near factory. a bearing that's been run OUT of oil will have many many many times worse wear than that.
how much have you taken apart on the motor? is it out of the car? is the head off?
I seriously doubt ANY wear has occurred on the crank with that miniscule amount of wear. I would certainly pull the oil pump, and inspect. it's relatively simple to do on a 240, or a N/A 617, so pull it, and heck, get a new pump drive shaft, and pump while you are at it, likely the pump itself has serious wear. you may want to have the cam towers checked for wear also, they are at the top of the oil passage, so low oil would hit them first I'd think.

now that I think on this, the bearings look like someone used S type oil instead of C type... AND left it in too long...
3K oil changes with dino, 5K with synthetic... bypass equipped filters are a MUST too... DON"T use the wix full flow!

vstech · #9 12-03-2011, 08:06 PM

BROKEN piston!!!

well there's your wear indicator right there!

likely the oil got REALLY old, and the wear on the cylinders is excessive, I bet there was no air filter in the motor either...

petecooke · #10 12-03-2011, 09:37 PM

The crank looks very clean and smooth. The bearing look like they took the wear, not the crank. I will take some pictures tomorrow of the crank and post them.

The engine is out of the car. The motor has a bent intake valve on the #3 cylinder. The head has be pulled and the machine shop has rebuilt the head.
Since I had the head off, I decided to replace all the rings and flex hone the cylinders.

When I noticed the wear on the connecting rod bearings, I figured I'd post the pics in this forum and get some feedback.

I guess I need to order a new set of bearings. My concern is that new bearing will wear differently with the crank if the crank is NOT machined. Is this usually the case or will I be ok with just replacing the bearings? I really don't want to completely rebuild this motor to spec. I will probably only drive it about 5k miles a year. It doesn't need to last another 300-500k miles. I'll be dead long before that.

Thanks for all the replies.

pete

t walgamuth · #11 12-03-2011, 10:05 PM

The only way to tell what you have on the crank is to mic the journals. If they are not too worn it might polish without being turned.

Have you determined what caused the broken valve? They don't just break.

bigblockchev · #12 12-03-2011, 10:13 PM

This will tell you the clearances & help to decide the course of action. Check the oil pump drive shaft. If i recall correctly the non turbo motors are driven by a shaft which runs off a bevel gear on the IP drive mechanism. the plug on top of the block can loosen, up the bevel gear rides up and the oil pump drive shaft goes with it, bingo the tang which should reach the oil pump no longer does. result no drive & no oil pressure. this actually happened to my buddys car , took us forever to figure that one out. Cheers Dan

DeliveryValve · #13 12-03-2011, 10:29 PM

Pictures of bearings can sometimes make them look worst than what they are. With that said, it appears the was some debris stuck in the middle of the bearing. How did the sump look internally? Was it clean or was there some sludge?

.

Diesel911 · #14 12-03-2011, 10:36 PM

"Plasitgage the bearings"

The above could only be done if He bought new Bearings. Doing it to the Old Bearings would be a waste of time.

Also Plastigage will not as easily tell you if the Crank is out of round. That is easier to do with a micrometer.

vstech · #15 12-03-2011, 10:48 PM

I would certainly pull the crank, and have a MACHINE shop inspect the crank. unless you have high quality micrometers, and the skill to use them on crank surfaces, it's best left to a machine shop.
they can also give you the current diameter and recommend what size bearing to install.
THEN you can put in new bearings and use plastigage...
oh, and of course, pull the oil pump and shaft, like we suggested above.