My 300 wagon blew it's oil filler cap off! Talk about pressure. it's physically broke. A few days later now I am having the engine stop problem, haven't checked for vacuum leaks yet, and I am wonderring if anyone sees a connection between these two events. Could it be related to biodeisel use. FOr the sake of all veggies I do hope not. Fuel filters changed 100 miles ago.
I have the slightest front end wag at idle and have been lazy about checking the rack dampner screw.
Also new to computers and this forum and wonderring where I may find or search for a used fuel sending unit/tank gauge.
thanks. bowlcole

BTW, Nothing in the archives under exploding oil filler caps.

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1972 220d Blew motor twice! ouch
1985 300TDT 169k
Many nissan pickups 86-89 200k plus
A vast portfolio of oldies
1949 chevy 1/2 ton
1947 international kb-3
1955 Cadillac coupe de ville
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1977 BMW R 100/7
1987 BMW K100RS
1985 Honda XR350
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The shutoff problem would probably be the vacuum switch either at the Injection Pump, or the Ignition Switch. As to the oil filler cap blowing off Sound like no crankcase ventilation. I'd check the PCV Hose to see if it's clogged. To check if you have excessive blowby I'd try running the engine with the cap off, if it puffs like a smokestack that's too much, A little blowby is normal. I'm sure other people with more experience have more input.

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83 240D four bagger stick diesel 276K

I'd like to see some of the old pros/ experts comment on this. I know diesels can run on their own crankcase vapors if sufficient quanity is availible. Is that a possible scenario in this event?

coleman kelly,

Try searching for threads on blow-by and crankcase ventilation. The cap blowing off sounds like your crankcase ventilation is plugged and you are eventually pressurizing the interior parts of the engine that are intended to remain at atmospheric pressure. It also sounds like this may have damaged your fuel shut-off mechanism, which works on vacuum. The vacuum can't shut the engine down if there is no intact diaphragm, or if the mechanism has been distorted and there is more than the as-designed resistance.

If you are not familiar with these devices, please be careful. There have been reports of runaway engine racing resulting in destruction of the engine if the shut off mechanism is not functional. Check the manual shut off lever and see if it is bound or free, and working.

I am not aware of how biodiesel might have caused this problem, but I would not rule much out at the moment. By the way, did the dipstick pop out of its hole? If not, you may just have had a really worn out oil filler cap and its failure may have had little to do with internal pressure build up. Good luck, 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)