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Plug at rear of valve cover....[200/85] posted by John K on
Thursday, 22 October 1998, at 8:51 p.m.
I've got a PVC problem. My 1985 240 - 166K keeps popping the plastic plug at the back of the valve cover. It never comes completely off so I don't loss any oil. But now I check it all the time and snap it back into place.
I've been good about changing the flame trap and oil trap box.....What else should I be checking??? No performance problems...
John
Re: Plug at rear of valve cover....[200/85] posted by Don Foster on
Thursday, 22 October 1998, at 9:07 p.m.
John --
If that plug is popping out, it almost certainly means you have positive pressure in the crankcase.
A way to check this is with the "jiggle" test. Loosen the oil filler cap, but leave it sitting in place with the engine idling. If you have positive pressure, the cap will jounce and bounce and jiggle around from the idling engine. But if you have appropriate crankcase vacuum, the cap will be pulled down and won't jiggle.
If you still have positive crankcase pressure, it probably means you've missed the small vacuum hose (easy to do, I did on my '86). The flame trap housing has a third small vacuum line that frequently plugs rock-hard solid. Replace it. Also check the fitting in the intake manifold the hose connects to -- it often plugs, and must be reamed out.
A good trick is to fasten a strap across the plug. On either side of the hole is a bolthole -- 6mm, I think -- used to mount the distributor when that engine is installed in a 700. You can fabricate a strap across the plug secured at each end by bolts (I did exactly this). IPD now sells an adapter for this.
But be aware that if you have crankcase pressure, you run the risk of additional problems. Engine seals and gaskets may be seeping, and on rare occasions you can pop a seal out of its housing. A popped rear main seal is a much bigger headache than that plug.
Friday, 23 October 1998, at 12:17 p.m.
replace plug (and valve cover gasket)...they sometimes loose their shape
and not fit right after they fall out
jv
(Shameless Plug - unrelated to Bricks)