That's what I paid for my used engine, and it's a good one. If your rod bearing is messed up, I think you need to take a real good look at the crank journal. Personally I don't think pulling the engine is that big a deal, and if you are going to get a used engine, you will be halfway there. There really is no substitute for working on an engine REMOVED from the car.

Pulling the engine is ...
 

Personally I don't think pulling the engine is that big a deal,

From January to March it can be...its easiest from May to June and Sept to November....the worst part is the rain right now.

I had some gusto even back in January, I rewired my whole Volvo engine management system..

So what happened to the 'Ring Job' part of this question ?

I'm not sure about the MB, but American undersized rod and main bearings are often marked on the backside of the bearing. I agree with the post earlier-if a bearing/surface got roughed up, I would definitely have the crank turned and the "big end" of the con rod checked. By the way, isn't piston clearance normally checked by using an internal micrometer on the cylinder in 3 or 4 different places and an external mike on the piston in the same way(or is the Benz different??)? I'd want to pull out all the oil gallery plugs, camshaft, and clean the daylights out of everything-I'd hate to go thru all that work and big $$$ just to suck a turbo!!! :eek: :eek: :eek: :pukeface:

Bullwinkle,

All oversize bearings, both rod and main, from MB engines I have seen have been marked with 0.25 mm, 0.50 mm etc. on the back of the bearing shell.

Connecting rod ends can be rebuilt if they are stretched. Some of the metal on the cap where it mates to the rod is ground off and the rod is reassembled and rebored. The rod has to be removed from the engine to do this.


BTW, crankshafts are not turned. That is a lathe term. A crankshaft is cylindrically ground on a special crank shaft grinding machine where tolerances can be held to a few 1/10,000 of an inch.

P E H

Carrameow,
If I remember right, aren't you the one that has worked on the Mazda rotary and the dreaded Volvo diesel? :eek: :eek: If you can keep the Volvo diesel going you can do anything! :D
From a person without engine rebuilding ability{me}, it sounds like you either need to find a donor engine, or another car and use this one for parts. I only say that as you mentioned rust, sagging seats, 325K! Why not just find your next MB, and get your 325K out of it?
I also commend you on being one of the most polite forum members whenever I see your posts. You're OK! :thumbsup:

So what happened to the 'Ring Job' part of this question ?
 

So what happened to the 'Ring Job' part of this question ?

the compression is 370 across all 5 cylinders; and she doesnt lose a drop of oil, I cant believe it...

Thanks JimmyL, that makes me feel good! Made my day.

don't be tooo suuure....

I once drove a Lincoln with the sweetest little long-stroke inline diesel one could ask for... A BMW 6-cyl ! :D

I think they only shipped a few of 'em....in....84-85 ?? something like that.

Ran like a swiss watch.

regardless, I agree completely, pull the motor.

I've had more than one case of a damaged bearing where the crank was still perfect. In fact, if anything, I'd say it's more common than having damage. At least in my own experience. Of course, I don't run them 30K miles after the knock starts... :D

In the heavy-equip diesels I work on, in-frame overhauls are far more common than pulling the engine out; and a crank will typically stay in spec for several sets of bearings (20K+ hours of hard time).

Dozer, Those big engines you work on probably have
1. Preoilers
2. Huge double filters maintained religously
3. A Repair schedule which would not allow them to be run after a knock was detected...as you mentioned..
4. Relatively few complete shutdowns and startups compared to our consumer automobiles.

Carrameow, I still don't understand why this thread had ' ring job' in the title...

Bullwinkle, Yes, that is how the MB piston to bore is measured also....but for the rod and crank bearings I believe the plastigage is better because it measures the area left after ' bearing crush ' .

On the subject of plastigage....
 

I've never seen this addressed; maybe i think about it too much, but what does plastigage measure?
Specifically, is it calibrated to measure the gap between the shaft and the bearing, or is calibrated to measure the total clearance? In other words, the clearances you read off the package--is that for one side of the clearance, or both? Boy I'm making this confusing, let ne try an example. Suppose you squash the plastigage and the package tells you that the measurement is is .0015 inches. Does that mean you have .0015 inch clearance all the way around, so that the the shaft is really .0030 inches smaller than the bore? Or does it mean that the shaft is only .0015 smaller than the bore so the clearance at any one point is only .00075 inch.

Am I over-analyzing this?

It is used in industry to measure other gaps... and they would not have any way of knowing if it were one part of a circle it was checking or just one space.... so it measures the space which would be left for oil between our rod and bearing at the point measured. The Mercedes manual gives the dimensions for each item.... and thus you get the gap by subtracting the numbers after careful measuring... but some manuals give the size as measured on the bottom of the bearing cap with the plastigauge.
My old Ford pickup truck has long had a ' thumping' noise in the engine.... when I got to reading about it I found that the factory had sent out some engines with too much clearance on the crank bearings....and specified putting oversized bearings in... and I think this was only on the cap side... to take up the slack. It was also recommended that one purchase the ' higher' grade plastigauage... a higher tolerance than normal... which I would think would be proper for our engines also....

Leathermang, you hit 3 or 4 out of 5 anyway... :D

Being poor miners, none of our equipment is new enough to have pre-oilers...

Although, the older and larger of the Cats -do- have pre-oiler, in a way.

The big main engine is started by a 'pony motor', a 2-cyl 25hp gasser. You fire that up, engage the drive to the main, and let it crank. It takes a good 30 seconds before oil-pressure starts to come up on the main (it's a BIG diesel motor... :D )

After it's been in the green for a bit, you turn off the compr-release, hit full fuel, and she rumbles to life. Of course, there -are- the jerks out there who start firing the main right after they engage the pony... :mad:

Cat also ran the pony exhaust pipe right up the middle of the main's intake-manifold (6' long inline-6), AND ran the main's coolant through the pony's water-jackets. So, if yer in Alaska, or even Minnesota :D , you'd just let the pony crank the main for maybe 5 minutes, pouring 50kw of heat through the exhaust and coolant, and THEN fire the main off.

It's really a great system, but unfortanately, the modern world doesn't seem mature enough to deal with waiting a minute; so all newer Cat's have electric-starters on them. blechh...

I guess it doesn't bother the guys who only own newer ones; but when yer used to seeing the oil hit 60psi before firing, on your older one, and you hop on one of your newer ones and hit the key, and she fires to life while that gauge is reading ZERO....man, it makes me cringe every time ! :D

he seems to enjoy rebuilding engines so let him do it his way. check his website.

lots of engines to rebuild.....so little time, should be on his license braacket.