Quote:
Originally Posted by jt20
2 things.
you are saying the force exerted by your hand on the VC will be greater than the pressure required to BLOW APART the cast aluminum valve cover. And, that the VC has the weakest seal on the engine. I find both of these very difficult to believe, please explain.
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Correct and the answer is in the theory of hydraulics. Let us assume you hold your thumb over the valve cover vent pipe sealing the crankcase and the pressure fails to move the pump shutoff diaphragm cutting the fuel. Let us also assume that the pressure rises to 10 psi.(as it would quickly with high blow-by). The area of the breather pipe is approx 1/2 square inch – i.e. a force of 5 lbs on your thumb. The area of the VC is approx 25in x 6in = 150 in² x 10 psi. A vertical force of 1,500lbs on this 3mm aluminum casting held down with 4 screws and this same pressure is pushing horizontally on the sides of the cover. We have the same story down below on the crankcase.
Quote:
Originally Posted by jt20
2nd- do you think that the absence of a postive crankcase ventilation system would cause harm to an engine? Lets say the the crankcase pressure only had to overcome atmospheric pressure at all times.
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If your breather were to be left open to atmos. you would always have positive pressure in the crankcase as blow-by is now being pushed out instead of being sucked out. Vacuum between T/C and filter is 4 to 5 inches at 3000rpm and increases with rpm – it’s not insignificant! Blow-by reaches a maximum under high load/high rpm. Crankcase pressure is undesirable, causes leaking F/E and R/E oil seals and in extreme cases as the subject of this thread can blow oil out of dipstick. My own 300D with 465k miles on original engine still passes the test I describe in a post above.
High blow-by, indicated by positive crankcase pressure, poor compression and high oil consumption that all go hand in hand is really decision time.
Realistically you have 3 options:
1) Sell now as a runner for what you can get if the car is not worth a rebuild.
2) Run it into the ground and sell to a junkyard.
3) If the car is worth a rebuild and you intend to keep for the long term, say 5 years or more, rebuild sooner rather than later. The longer you leave it the more it will cost and you may as well have the benefit of the new engine now rather than in a year or two.
Have a nice day