Question on Lazy man's ring job on a 85 300D?
 

I got a knock in my 85 300D from when I plugged the breather and lost oil.
I'm trying to do the Piston connecting rod bearings without removing the engine. To do them I have to remove the huge lower oil pan.
The huge lower oil pan consists of the main large pan and a smaller pan underneath it. By removing the smaller pan and part of the oil pump, you can reach two of the piston bearings but to reach all five, you have to remove the main pan.
The #1 piston bearing was a mess. #2 was okay. The front main bearing was okay.
The larger oil pan--can it be removed? I am asking myself that question now. My biggest concern are the front rubber crank seal and the rear seal.
My question is WILL THE SEALS HAVE AN IMPACT on THIS JOB? Also there may be some interference with the front timing gear.
My theory is that even if you unbolt the lower pan, the engine crossmember will block you, so you will have to undo the mounts and raise the engine.
You may not be able to remove the main pan completely, but you may be able to tip it or rock it to get to the rear 3 pistons. The job will be messy because oil will drip all over your face. If the seals will cooperate I will do it. The engine is basically great, believe it or not.
I wont know for another few days..

What size connecting rod bearings do you use?
 

The catalog list 52, 51.75, 51.5 mm rod bearings. Assuming crankshaft wear, would you select the smaller size (51.5 mm) bearings?

Save yourself a boatload of grief and pull the engine... You will need to replace the seals, the rear seal will require you to remove the crankshaft.

If you will tell us who gave you the idea this was possible or legit we will tar and feather them for you.....

plastiguage the bearings after you put them in...just to be certain clearances are in spec....it would ruin your day to find out they weren't after you put it back together and find out the hard way.

I vote on pulling the engins and doing the seals too....if they aren't leaking already they are likely to do so soon....

Not pulling the engine--
 

I still think its possible in all due respect.
Anyway I have nothing to lose. If I fail I pull the engine anyway.
I know someone who did it this way on a Lincoln.

The fact that you have to ask which size bearings is an indicator you are not an experienced engine rebuilder... which is different from removing and replacing parts on the rest of the car.....
The size bearings are not determined until you have taken the rods off the crank throw and put the plastigage on them and retorqued them... then you take it off and carefully inspect how much it was crushed comparing it to the ' guage' on the paper container the plasti-guage came in.
Then you order your proper size bearing.
That Lincoln was not a long stroke inline engine. And it was not a diesel.... where tolerances are much closer than most American made gas engines ever considered being...
But it won't hurt for you to try if you are well versed enough to tell when you have hit a procedure which you can not continue from underneath and do well... that is the point at which you change to normal rules...if you are to not lose your efforts from trying it this way...

Yank it!
 

Do yourself a favor man.!!
Pull it out!
You can do it ....We can help!!
Ask me how I know!

Undersize rod bearings aren't made to take up "slack". They are to be used on a crank that has been turned (machined).

Talk about a disaster waiting to happen!!
 

If bearing #1 is messed up you are well beyond the cheap fix stage. Find a replacement motor or sell the car and move on....

I just do not see where you will save any effort nor any time by trying to get the lower engine case off with out pulling the engine. It is tough enough to get off with the engine out and on a stand.
The rear seal is just a length of braided stuff that needs to be trimmed to fit in the rear bearing cap and in the block. Problem there is that the lower engine case has to come off and the crankshaft needs to be lifted to get to it. There are two pins that poke into the seal, one is easy, it is in the bearing cap. The other is in the block. Front seal is accessable from the front of the engine.
I think I would look at least look at a new oil pump and chain while I was in there. With what you have I would seriously consider having the crank turned and oversize bearings. Nothing less than a crank polish and a new set of main and rod bearings.

I replaced the rods and mains on a TR-7 in situ once. Even though I had the car over a pit, it was dicey. I would never do that again- at least not in a car that has a crossmember or a 617 with the lower pan and the rope seal. It took me a looong time and I was very concerned about getting dirt in the bearings. My conclusion was that it would have been quicker to pull the engine. I suspect you will agree if you continue

Boy I wish I were young again..
 

The fact that you have to ask which size bearings is an indicator you are not an experienced engine rebuilder...by leathermang


When I was young I was very competitive and something like this would get me motivated.
I mean all of us are stubborn and tuff or we wouldnt be doing this..but I'm 45 now, at this age we all got other stuff on our minds...
Mr leathermang, you will be 45 someday...

Carrameow, just ignore him. He gets all cranky when his back is bothering him and he cannot go out and mow the grass. :D

I do have to agree with him regarding pulling the engine. I know that you are a very resourceful fellow and, if I had to bet, I would say that you will get this job done with the engine in the vehicle.

But, I would be very concerned that you will make an error in the process and have to do it all over again. There is significant risk when working upside down in unfamiliar territory.

Thanks Brian!
 

If I lived near you, I would help you do anything!

Ohhhhh, Greg........................don't you wish!!! :D

Likewise. I need your motivation and karma!! ;)

Leathermang is past 45..............in fact he is past 55 ....check his profile..

Heck that makes me feel good!
 

The reason I keep wrenching is to stay young!
Thanks for the motivation, Leathermang.
Yes I never used plastiguage I got by on an inner micrometer and an outside micrometer and a dial indicator and blocks, and a straight edge thats all I used for all of my engines. You may not need palstiguage unless you are blueprinting. You just cant afford everything. There was a day when there was no Internet and Fedex and EBAY and you couldnt buy everything everyday.

I got a liitle distracted recently by Turbo gas motors and computerized engine controls..

Anyway being 45 has its advantages i will pull the engine starting this weekend.

"When I was young I was very competitive and something like this would get me motivated."

I already tried the short route on so many things... and discovered it was actually the long route... I am trying to save you from having to learn this the hard way on a nice engine...

Another thing to consider is what you consider success.... it may be different from what all these old conservative guys are thinking about when they posted in this thread...
I think that you should be able to run your engine to the same point that the rings would have worn out had you not acquired this knock.. if you do this correctly... you may consider getting 10,000 miles more out of this engine as success.... I don't know... and it won't be my money or knuckles hurt by experimenting on your engine... could be a lot of fun to watch if you are honest about what you run into trying it... But we had to be honest in our opinions.. or we would not be able to say " I Told You So ! " afterwards (if you don't follow our advise ) :D .....

PlastiGuage is a Godsend for normal mechanics.. you have way more invested in those tools you mentioned that what it would cost to Plastiguage several engines ......
Even nicer is the fact that most people will get WAY closer to accurate with the plastiguage than with your equipment... which I know takes " FEEL" and practice to use...

http://www.plastigauge.com/

"There is significant risk when working upside down in unfamiliar territory."

Try twice having to get hold of my eye doctor to remove flecks of rust on my eyeball late in the evening or a weekend... ... very hard to see straight up... and then all that oil following gravity's wishes straight at you.... and trying to wear goggles in a hot humid climate... and needing great light to check things... and trying to keep your arms raised above you for long periods of time... and then when you graduate to bifocals... FORGET IT !!!

I just ordered some Plastigage from Summit Racing for a M117 motor I am working on for one of the 300SELs. I wish there was something similar for piston skirt clearance...

And because of that, nowadays the only route Greg will even begin to consider is the long one.

Aren't bifocals wonderful? Let's see--the top isn't right I'll try the bottom. That isn't right either. Oh hell I'll do it by the Braille system.

Carrameow, sorry I'm coming into this late but I'm happy to see you are considering removing the engine. It really isn't too bad if you pull it with the trans. The last time I did it I put huge turnbuckles on the engine tilter and it made a big difference in ease. Once you get that engine on a stand and take off that upper pan you will be glad you did. Some of those allen screws seem to be such a risk to strip out even under ideal conditions - if you try to take that upper pan off in situ, I think that would be enough to make you give up on MB forever - I really think that it would do that for me. :eek:

I have always thought that when you refresh an engine unless you refresh the accessories also you have really not increased your reliability very much. So I would pull the engine and refresh the alternator, starter, engine mounts, etc while you are at it.

If the car is not rust free I would not do this job.

Didn't you rebuild your 240 engine?

"Aren't bifocals wonderful? Let's see--the top isn't right I'll try the bottom. That isn't right either."-- J.R.B.

After long consideration I have decided that my arms are the wrong length.

Carrameow,

To use oversize bearings, sometimes called undersize bearings, the crankshaft must be reground. I had a rod bearing journal reground with the crankshaft in the engine in the car once but I don't know if there is enough room in a MB engine to have it done or if the process is still done.

Is it the bearing that is bad or is the rod journal also bad. You can usually tell if the journal is bad if it feels rough to the touch. You might measure journal with a micrometer to see if it is out of round.

I don't know how deep the hardening goes, so the journal might have to be rough ground, rehardened and finish ground.

P E H

Why i considered the Lazy man alternative...
 

I got my 325 K from the car; and it went 30K even with the knocking...the car has started to rust, also. The seats are saggy.
I know all of us can make these cars last forever...but..when is enuff enuff..
Please dont get me wrong i don't do things half-a__ed --I considered rebuilding the motor, but when i rebuilt my 240D transmission and engine , a year later the car got totaled..

I can pick up a used motor for $400 maybe.

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.