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  #1  
Old 08-26-2004, 11:31 AM
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Join Date: May 2002
Location: SouthCoast, MA
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"1982 240D... needs rings" - what do you think they mean?

Saw this add today... what would be your best guess as to what this car needs to have done?

$500, 1982 Mercedes 240D 185K, Lots of new parts, needs rings. $500 OBO. For restoration or parts. 610-258-7742

thanks

ps - I can't really afford another car, so feel free to call and grab it for yourself... before I convince myself otherwise...
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  #2  
Old 08-26-2004, 11:34 AM
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Stella!
 
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It means that they think it needs rings. What it really needs remains to be seen.
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  #3  
Old 08-26-2004, 12:07 PM
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Maybe I can be of more help;

A common symptom of high mileage cars among "many" others of course, are Worn Piston Rings. There a a few techniques to determine if this is the problem.

Piston Rings seal the Pistons against the cylinder walls to create a near air tight seal. This will allow the cylinders to produce compression (more important in diesels) during the "compassion stroke". With out adequate compression and engine will have blow-by, burn oil, and smoke and lose power or not run at all. Other problems can however cause the same symptoms such as worn value guides and or valve seats, indicating a need for a valve job. Rings require an engine tear down, valves send the head out to a shop.

While doing a compression test measure each cylinder and compare it to factory spec and look for a problem cylinder. Squirt a bit of oil into the problem cylinder and retest. A temporary rise in compression pressure will indicate worn rings. If there is no change, then valves are the most likely cause, then cracked rings, etc....... Of course you can never be sure until you pull the motor apart. In aviation we normally will put a bore scope into the cylinder to have a little look-see before doing anything.

Hope that helps a little.
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  #4  
Old 08-26-2004, 12:54 PM
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Just fix it
 
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Quote:
Originally Posted by 97E300D
Squirt a bit of oil into the problem cylinder and retest. A temporary rise in compression pressure will indicate worn rings. If there is no change, then valves are the most likely cause, then cracked rings, etc.......
Hope that helps a little.
On a diesel I would squirt a bit of oil and then crank the engine with the combustion chamber open before doing a compression check. This will allow excess oil to be expelled but leave the cylinder coated with oil. There is a very small risk but a serious risk that the cylinder could fire or go hydraulic and do some damage if you squirt too much oil in the cylinder.
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  #5  
Old 08-26-2004, 01:32 PM
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Yep, your probably right. It would be best to disable the injector pump during the test, since the engine could fire on the compression. It is a diesel after all. A static leak down test could also show an indication of rings, but in the field it may be more difficult.
What is the approved method of compression testing on a diesel? The oil my not be the best option if it could act as detontation fuel.
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  #6  
Old 08-26-2004, 03:48 PM
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A cylinder leak down test could provide the same information and point towards the rings OR towards the valves.... in one test... except you can't squirt the oil onto the top of the piston on a horizontal bore engine....
97E300D, Do you own a borescope ?
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