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  #1  
Old 04-07-2008, 11:20 PM
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83 240D low compression in 1 cylinder is it terminal?

Hey all- I just bought an 83 240D to add to my collection! It supposedly had a bad transmission but when I looked at it I could tell the linkage was just worn out.(no bushings in any of the shift rod ends) So I bought it for $300 and had it towed home. At home I started it up and it ran rough at idle and low speed but seemed ok at higher speed. So I replaced the shifter bushings and did a valve adjustment but it still ran rough,so I did my first diesel compression test. From front to back it was 300-350-350-100. I squirted some oil into the cylinder through the glow plug hole and the reading came up to about 200. I did do a search on this forum, and there was one post about the rings being stuck from using WVO. I think this car may have been run on WVO or other alternative fuel as it came from Santa Cruz and looked to be well abused. Also the glow plugs were oily and had a funny smell when I pulled them. So, what are the chances that I can get lucky and unstick the rings? Any tricks I should try? The post I read mentioned Marvel mystery oil. If I try that where do I put it in at- the injector bore or the glow plug hole? If it turns out to be a parts car at least it had a new lifetime warranty starter in the trunk! Thanks to all who reply-Scott

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Old 04-07-2008, 11:47 PM
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the cyl that is low is 4 they are numbered front to back... MMO in the cyl might unstick the rings and synthetic oil might help..

AFAIK the only thing that a low compression cyl will do is cause hard starts
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Old 04-07-2008, 11:57 PM
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drive it HARD

on diesel
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Old 04-07-2008, 11:59 PM
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Adjust valves too.

Tom W
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Old 04-08-2008, 12:05 AM
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Quote:
Originally Posted by 10fords View Post
and did a valve adjustment but it still ran rough,
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Old 04-08-2008, 12:43 AM
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I should add that it starts up fine, even cold. one other thing- when I was spraying carb cleaner around the intake/exhaust manifold gasket it caused a dramatic rise in rpm. I know the gasket is leaking, but that couldn't cause rough idle and low compression could it?? -Scott
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Old 04-08-2008, 12:58 AM
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Driving it for awhile on biodiesel if you can get it in your area should help to clean the engine up. Another trick I used that I was taught at Chrysler was to slowly inject water into a running engine at about 3500 RPM to help get piston rings unstuck, but I have no idea how well this will work with vegetable oil! I would drive it on biodiesel or diesel for awhile first.
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Old 04-08-2008, 01:03 AM
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How much do you know about diesels? not trying to be rude, but couldn;t word it any other way. ( incase you don't know about run-away diesels)

Brake/carb cleaner acts like starting fluid (ether) and is pretty bad for diesels as most members will agree. I would assume that if you had a big enough leak in the intake Man. that it could cause the RPM to rise. Did you you hear alot of knocking?
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Old 04-08-2008, 01:08 AM
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No knocking- actually seemed to run smooth, but that was probably from the higher rpm.-Scott
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Old 04-09-2008, 01:15 AM
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So , back to my original question, is it likely that it's just a stuck ring or a worn out one?-Scott
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  #11  
Old 04-09-2008, 07:32 AM
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Quote:
Originally Posted by kerry View Post
Doh!

Tom W
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..I also have a 427 Cobra replica with an aluminum chassis.
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Old 04-09-2008, 09:18 AM
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Even though you adjusted the valves carbon, or whatever, could have built up between the valve and seat still leaving it open. This is where the water spray can help. Or a soaking of Marvel yet spin it over with the glow out so not to hydro lock her up.

A stuck ring treatment, per my German factory trained and probably the most knowledgable Mercedes mech. I ever met, drain the case new filter add 4 qts Marvel Mystery and 4 Qts ATF and drive that puppy. Boy I was scared yet oh man does it work and wow what a clean motor afterward.

Yet first did you do a leak down?
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  #13  
Old 04-09-2008, 11:00 AM
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I haven't done a leakdown test yet. since the compression came up when I squirted in some oil I am assuming it is ring related. What I'm trying to find out is if the rings are toasted or just stuck. Since the 240D motor seems to be almost bulletproof I'm hoping its just stuck! I think I'll go ahead and try the various methods to unstick the rings and see what happens. Please keep the advice coming and I'll post the results. Thanks-Scott
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  #14  
Old 04-09-2008, 11:05 AM
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MM oil and ATF

Dave, with your 4 qts MM oil, and 4 qts ATF, did you cure a compression problem? How long, or how many miles, did you run this mixture?

I have a 220D run ?miles without thermostat by PO. It has the following readings: 290 - 180 -150 - 290 on a 40K "rebuilt" engine. The engine starts hard, runs rough until warm, and puts out a lot of blue smoke for the first 5 minutes or so. Maybe I should try your suggestion before I tear it down?

Ron
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  #15  
Old 04-09-2008, 11:37 AM
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Quote:
Originally Posted by myssrhl View Post

A stuck ring treatment, per my German factory trained and probably the most knowledgable Mercedes mech. I ever met, drain the case new filter add 4 qts Marvel Mystery and 4 Qts ATF and drive that puppy. Boy I was scared yet oh man does it work and wow what a clean motor afterward.

Yet first did you do a leak down?
Where do you put the 4qts MM oil + 4qts ATF?
If it replaces the engine oil how long do you drive it like that?

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