Diesel RVs: Re: [diesel_mercedes] Anyone want to buy my '81 300D? Not really. Just tell ...

My comments...

1) STOP running the engine. Something is wrong and only will cause more damage.

2) overfill the engine with kerosene. It will leak out of any bearings/seals that were damaged.

3) check for leaks, Push back and forth on the vibration damper/pulleys on the front of the engine.

4) drain and drop the oil pan.

5) look at the lower bearings on the crankshaft to pushrods. Look at the upper piston/rod bearings if you can. check for looseness on the pushrods.

6) The number one bearings that fail would be lower bearings. The crankshaft bearing turns 360 degrees and is hammered by the one firing piston. It is the most abused bearing that turns 360 degrees with uneven forces. When you run low on oil, usually it is only the front rod bearing or the rear one. The oil would have flowed to the front or to the back, leaving an end one dry.

These are probably brass bushings, captured inbetween the pushrod and the end cap. remove the screws and remove the damaged (missing bearing) and replace. They sell oversized ones if there is wear.

If you have run the engine enough to slam the pushrods into the crankshaft and damage it, try using emery cloth to clean up any bumps. You need the camshaft to be slick to not spin the bearing and shred it.

Engines will run (inefficiently) with bad piston rings, etc. But if you throw a rod through the side of the engine, it won't run long. And you will leave alot of oil on the car driving behind you.

disclaimer. I have never torn apart a mercedes(yet?). Some small differences may exist.

Carl

On 10/13/2011 3:15 AM, Bobby Yates Emory wrote:

Trish,

Amen to Tom's comments. I have also done a repair only to find that it was not needed.

Let us know what you find and the guys who know can suggest what to test.

This may involve some small expenses and dirty fingers, but may save you paying big repair bills.

(Reality note - it may be a really busted engine - but then again, it may not be.)

Bobby

On Thu, Oct 13, 2011 at 1:35 AM, <audiolaw@aol.com> wrote:

Trish,

    When bad things happen, people can panic or jump to conclusions. It sounds like something has happened with your car, but you need to step back and contemplate the possibilities.

    First, you have to remember what you have - a diesel, with an overhead cam engine. The overhead cam is driven by a chain. The valves don't have lifters associated with them.

    This is partially good for you, because taking the valve cover off is a normal task associated with adjusting the valves (every 15,000 miles, and when you first take possession).   With the valve cover off, you get to look at the complete cam shaft, the top of the drive chain (front end of the cam) and all the valves and springs and rockers, etc.

    Next, think about that dieselness of the engine. No spark ignition system to worry about, so all the electrical complication comes down to one simple question - are the glow plugs heating the prechambers before you start? If not, that's a problem to be addressed, separately from any banging noises.

    The engine itself only needs THREE things to run: 1) Fuel, properly delivered; 2) Air, sufficiently delivered; 3) Clear exhaust to vent the combusted gases. Before you start digging into the engine, you must establish that each of these three is taken care of.

1)    Is it possible that the injector pump broke? That could make some unpleasant noises. Or that some other mechanism is causing a failure of fuel delivery to the cylinders?

2)    Did something get into the air intake and crap up air flow to the engine, starving it so that it can keep running? Since your's is a non-turbo, this is easier to scope out.

3)    Has anything clogged up your exhaust line? When you get it running, even briefly, is it putting out exhaust?

    Stay with the exhaust for a minute. If it is firing, is the exhaust smoke brown/black (unburned fuel) or blue white (burning oil) or steam white (water)? If it isn't blue/white, then the engine may still be OK.

    Don't tear the engine down, or rip it out, or anything else until you've figured out what's happening. You tell us that it cranks and will run for a little while. What noises is it making during that process? What smoke or other things are coming out, and where are they coming out from?

    Remember why you got this - these engines are tough buggers. YES it was wrong to let it get low on oil. But if there was sufficient oil to run the oil pressure guage, and it wasn't puffing out oil smoke, it may be that the low oil only has you confused and is not really related to your problem. (You wouldn't be the first person to have been confused about a problem - don't ask me how I know that.)

    Step back, take a few breaths, and then start to diagnose it the way you would a problem with any other machine or with a sick animal. Check each system / organ and make notes of the symptoms. ONLY AFTER that will you be ready and able to start diagnosing the problem.

Tom