617 combustion chamber - how to add oil? - Page 4 - PeachParts Mercedes-Benz Forum

leathermang · #46 01-19-2007, 01:51 PM

Quote:

Originally Posted by Shorebilly

In all actuality, piston rings are pressed against the cylinder wall by the gasses of combustion......the spring in the ring is there to initially hold it against the cylinder wall.....
I really don't feel like looking this up and typing a whole paragraph on the exact design principles.....but I will if I must...!!!
SB

The chamfer on the top inside of the piston ring is for the purpose of utilizing combustion pressures to AID in pressing the ring outward to keep it in contact with the cylinder wall..

But you would not need to use a ring compressor to install pistons if that were ALL the story.

Our engines have two compression rings and one oil ring... while significant outward pressure might be available for the top ring... that leaves compression ring two and the oil ring needing something else... for the oil ring an Expander Spring is placed under it.

As an engine wears ... Vstech 's description comes into play... as those rings flex going up and down the bore they eventually lose their springing action...

Your need to throw ' credentials' into the discussion should be a warning flag to others..if you can't explain something with examples of logic and physics ( and a little human nature thrown in ) something is missing...

Your statement concerning ' washing down the cylinder walls " potential is amusing... try computing the actual fluid involved in my ' three second burst while the engine is turning' and try to remember that the piston has oil holes behind the rings... there is no way for what I have suggested to come remotely close to having any potential for damage due to lubrication washing from a solvent condensing on those ' cold ' bores...

And to anyone who might be trying to qualify as nitwit.... I AM a farmer... and you have no sense of humor.

leathermang · #47 01-19-2007, 01:58 PM

Quote:

Originally Posted by rrgrassi

No, not easy, a real PITA on diesels and gassers, not to mention time consuming, but better than paying some shop to do the same testing, and better than tearing into the wrong part of the engine.
On diesel I prefer to add oil through the GP hole. Gassers is always the spark plug hole. I also use the GP hole for the compression testing. I use an old metal oil can with the small flexible spout to add oil for compression testing. I only add oil if the initial test results in one or two cylinders with lower reading than the others.

I have no problem with the concept of using oil to check the sealing capacity ( or lack of it ).
But you could to the SAME thing while attaching a Leak Down Tester to your engine... AND not have the potential of the (diesel ) engine starting up on you when you hit the starter... not that kind of problem with a gas engine.. but getting that much oil down into the bore through the glow plug hole.. or even the injector hole... through those TINY RADIALLY drilled holes in the precombustion chamber... seems to be more in keeping with the leak down machinery... since that would actually work to force the oil through those tiny holes... whatever oil is in the precombustion chamber when trying a compression test could be a problem.

kafer65 · #48 01-19-2007, 04:31 PM

SeaFoam top end cleaner does the same thing as the water. I have been told by mechanics that using water to free carbon deposits like described on gas motors works. Just my $.02.

rrgrassi · #49 01-19-2007, 04:58 PM

Quote:

Originally Posted by leathermang

I have no problem with the concept of using oil to check the sealing capacity ( or lack of it ).
But you could to the SAME thing while attaching a Leak Down Tester to your engine... AND not have the potential of the (diesel ) engine starting up on you when you hit the starter... not that kind of problem with a gas engine.. but getting that much oil down into the bore through the glow plug hole.. or even the injector hole... through those TINY RADIALLY drilled holes in the precombustion chamber... seems to be more in keeping with the leak down machinery... since that would actually work to force the oil through those tiny holes... whatever oil is in the precombustion chamber when trying a compression test could be a problem.

That is one reason why I leave out the GP's when doing a test. No chance of starting, and only the jug with pressure is the one being tested. The only problem with a leak down is that you can't tell for certain if it's only the rings. Also the rings could be sealed fine since a leak down is done a BDC (Bottom Dead Center). Bores tend to wallow a bit in the center because of thrust angle on the wrist pin in relation to rod postition. I was taught to always start with a compression test.

My teaching was:

1. Dry compression test, looking for large differences in readings.
2. Wet compression test. If readings come up on the lower reading bores, then rings are suspect. If on a diesel, a little compressed air can force the oil down to the cumbustion chamber.
3. Leak down test to test for cracks, bad head gaskets, burned or valves not closing properly.
4. Tear down and repair or better yet, rebuild unless it was just a bad head gasket.

Only a tear down reveals the final conclusion, unless visible signs like coolant or oil leaks are seen, or bubbles in the coolant, or oil/coolant mixing.

I grew up ranching, spent time in the city after college, and am now living back out in the sticks. I prefer farm/ranch living to city life. I do have a sense of humor, so I'm ok unless some one attacks me on a personal level. Once it becomes personal, lines have been crossed IMHO.

captainmonk · #50 01-19-2007, 05:30 PM

i'm a simple folk fisherman compared to to a simple rock fisherman I guess Should i just stick my 2 inch was down hose in the engine room of the boat for a few hours?