Quote:
Originally Posted by TMAllison
Guessing that when the plug gets weak and then stops glowing is when "most" of the carbon collects. When working, they get red hot; something like 1200F.
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Actually they shut off when the car is running after a short period of "afterglow" which sounds almost pornographic. The driving style, and I suspect, the EGR flow, lead to conditions of higher soot formation inside the engine. We don't notice this as an external soot discharge from the engine because of that soot oxydizing catalyst drum in the exhaust. But lots of loafing around will pack carbon inside the crevices in the prechamber. And, once the carbon is there it is a good thermal conductor - much better than air - and it draws the heat from the plug into the prechamber. The larger mass of the prechamber and cylinder head will prevent the plug itself from burning away any soot deposits completely, and may contribute to hardening it in place.
Find a long hill and after all is at normal operating temperatures take a run with the throttle pretty much wide open up the hill. Take a few passes. The idea is to get the temperatures up and flow rates up so you can burn off some of that stuff before you attempt to pull your glow plugs.
I have been relatively fortunate - I have not had any plugs stick and, changing them only as they fail, I have changed all 6 twice now. One was actually no more than hand tight the first time I tried (number 6), leaving me to suspect the dealer did that one in the past without taking the manifold off. And I have taken to using the car wash bays for DIY with the high pressure nozzles as the place to clean my manifold out. Does a great job on about 85% or more of the inside in about 3 to 5 minutes. Takes longer to clean out the bay.
Jim
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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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