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#1
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89 300E Fouled Plugs
My trustworthy mechanic has discovered that I've got oil fouling all my spark plugs. The engine is, consequently, missing incredibly and running extremely rough. Also, I have very little power. The compression is good and I'm not turning out blue smoke.
So, does anyone have any ideas on how the oil is getting into the cylinders? |
#2
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are you using platinum plugs? this engine doesn't like them and fouls them.
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2005 Mercedes C230k sport sedan, 6 speed 1987 Porsche 924S - 968-engined track car |
#3
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Valve guide oil seals, undoubtably.
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Steve Brotherton Continental Imports Gainesville FL Bosch Master, ASE Master, L1 33 years MB technician |
#4
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What's your measured rate of oil consumption - mile per quart.
Even if it gets down to a quart in less than 300 miles the proper Bosch H9DC plugs should not foul. High oil consumption will cause a lot of black deposit buildup on the metal shell, but that's not fouling. Fouling is heavy deposit buildup on the insulators and the insulators on H9DCs should only have minor white to tan deposit buildup, even if oil consumption is high. Duke |
#5
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I've spoken to my mechanic and he replaced the valve guide oil seals earlier, when the head was machined. Oil consumption is around a quart every 300-400 miles.
My mechanic is trying to avoid a rebuild. I'd like to do the same. |
#6
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If oil consumption is a quart every 300-400 AFTER the valve guide seals were replaced then the valve guides are probably worn. This is common on M103 engines, but even at that rate Bosche H9DC plugs should not foul.
You didn't mention the plug mfg. and number you are using. Care to let us know? Duke |
#7
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If the valve guides were bad, would that cause the same problem as bad valve guide seals? The seals have been replaced and the plugs are the correct ones.
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#8
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If the guides are severely worn new valve seals may not improve oil consumption or only improve it marginally. My Cosworth Vega uses the same plug (geometry and heat range) as the M103 (except a resistor version and the NGK TR5 is my choice), and it got down to a quart every 200 or less before I pulled the head and replaced the guides and seals, but even at that rate of oil consumption it did not foul the plugs and ran great.
Duke |
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