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Mercedes Model: 1978, 250, 6Cyl, Gasoline: Chasis: 123026-20-044500, Engine: 123920-20-021475
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41 Posts
Discussion Starter #1
Unfortunately this is a stage the Engine has come to. However it seems to be sudden and resent, although no major event took place. The car has usually been neglected and standing for prolonged periods of time.

I read up on several posts regarding reasons and have taken following steps:
1. removed the blow by pipe from the Air Cleaner box, so it does not cycle back the EGR - Exhaust gas recirculation into the combustion chamber.
2. changed the oil and filter. I was told that sometimes the choice of Oil makes a difference. I was advised to use fully synthetic oil so I have changed it to SAE 5W-40.

Could anyone advise if this is the right choice.
Any other advice.
 

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'89 300E Turbo project, ‘85 Audi Coupe Quattro, ‘71 BMW turbo 2002, '73 BMW 2002tii, ‘67 Kaiser M725
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17,692 Posts
If you get a few days to let it sit, pour some Marvels Mystery Oil into the spark plug holes and let soak. This could free up gummy piston rings and take away some of the blow by.
 

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2008 AMG CLK63 Conv., 2012 R350 4-Matic, Wife's 2015 C300 sedan
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+1


In my University days I had a Yamaha 550 that spent the winters parked up. Thing was a beech to start in the spring, fortunately my parents lived at the top of a very steep hill.

Only years later did someone tell me to put a teaspoon of engine oil down the spark plug holes when I parked it up, then repeat before thawing out in the spring.
 

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Mercedes Model: 1978, 250, 6Cyl, Gasoline: Chasis: 123026-20-044500, Engine: 123920-20-021475
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41 Posts
Discussion Starter #4
If you get a few days to let it sit, pour some Marvels Mystery Oil into the spark plug holes and let soak. This could free up gummy piston rings and take away some of the blow by.
this is an interesting concept, could you shed light on how much per cylinder.
Also let soak for how long?

most importantly what’s the concept of gumming up that potentially causes blow by
 

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Registered
Mercedes Model: 1978, 250, 6Cyl, Gasoline: Chasis: 123026-20-044500, Engine: 123920-20-021475
Joined
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41 Posts
Discussion Starter #5
+1


In my University days I had a Yamaha 550 that spent the winters parked up. Thing was a beech to start in the spring, fortunately my parents lived at the top of a very steep hill.

Only years later did someone tell me to put a teaspoon of engine oil down the spark plug holes when I parked it up, then repeat before thawing out in the spring.
Could you shed some light on the cause of how gumming causes blow by and how this remedy Works
 

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2008 AMG CLK63 Conv., 2012 R350 4-Matic, Wife's 2015 C300 sedan
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9,964 Posts
Gumming up occurs when combustion residue and oil combine and harden in the piston rings grooves preventing them from moving freely. To form effective seals against the piston bore they need to press against it. Moreover when the engine warms up, the piston rings warm up, they expand, the gaps between the ends of the piston rings close up, the grooves in the piston close up and the rings press more firmly against the cylinder bore. QED if they're stuck in their grooves they can't move freely and don't seal as well.

Adding engine oil before a start from long term storage provides both initial lubrication and helps create a temporary seal.
 

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'89 300E Turbo project, ‘85 Audi Coupe Quattro, ‘71 BMW turbo 2002, '73 BMW 2002tii, ‘67 Kaiser M725
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17,692 Posts
this is an interesting concept, could you shed light on how much per cylinder.
Also let soak for how long?

most importantly what’s the concept of gumming up that potentially causes blow by
1-2 oz per cylinder, make sure car is on level ground. 1 day is good, 2 days is even better.

Before putting spark plugs back in, place a towel/s over spark plug holes to blow out any remaining MMO via cranking engine.

Expect smoking for first 5-10 minutes of running while MMO burns off inside combustion chamber.
 

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Mercedes Model: 1978, 250, 6Cyl, Gasoline: Chasis: 123026-20-044500, Engine: 123920-20-021475
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41 Posts
Discussion Starter #8
Gumming up occurs when combustion residue and oil combine and harden in the piston rings grooves preventing them from moving freely. To form effective seals against the piston bore they need to press against it. Moreover when the engine warms up, the piston rings warm up, they expand, the gaps between the ends of the piston rings close up, the grooves in the piston close up and the rings press more firmly against the cylinder bore. QED if they're stuck in their grooves they can't move freely and don't seal as well.

Adding engine oil before a start from long term storage provides both initial lubrication and helps create a temporary seal.
1-2 oz per cylinder, make sure car is on level ground. 1 day is good, 2 days is even better.

Before putting spark plugs back in, place a towel/s over spark plug holes to blow out any remaining MMO via cranking engine.

Expect smoking for first 5-10 minutes of running while MMO burns off inside combustion chamber.
sorry for being an amateur, but I just want to be sure, you’re saying I should open plugs, pour MMO into combustion chamber, leave plug ports open for 2 days, crank it while plug ports remain open to drain out over flowing MMO, then start?
 

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Mercedes Model: 1978, 250, 6Cyl, Gasoline: Chasis: 123026-20-044500, Engine: 123920-20-021475
Joined
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41 Posts
Discussion Starter #9
1-2 oz per cylinder, make sure car is on level ground. 1 day is good, 2 days is even better.

Before putting spark plugs back in, place a towel/s over spark plug holes to blow out any remaining MMO via cranking engine.

Expect smoking for first 5-10 minutes of running while MMO burns off inside combustion chamber.
MMO seems to be unavailable here, any alternate?
 

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'89 300E Turbo project, ‘85 Audi Coupe Quattro, ‘71 BMW turbo 2002, '73 BMW 2002tii, ‘67 Kaiser M725
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17,692 Posts
50/50 mix of acetone and dextron/mercon transmission fluid works
 
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