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Re: sorry john but it dosnt dissipate overnight..
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Posted by trog100 [Email] (more from trog100) on Tue, 21 Jan 2003 23:33:49 Share Post by Email
In Reply to: Re: when still cold, but after running, JohnK, Tue, 21 Jan 2003 17:16:14
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with a small initial leak the pressure gets into the cylinders during the combustion proccess.. not exactly sure how high the pressure is in the cylinders when they are under load during the fireing stroke but its high.. far higher than cranking pressures.. once in the cooling system it stays there assuming the system is otherwise leak free.. in fact the cooling system maintains a constant 15 psi all the time whether the car us running or not.. a very small and slow pressure release occurs between cylinder and waterway.. the cap lets this go at 15 psi.. if it didnt the system would blow very quickly.. but once in there the pressure stays in there it does not dissipate overnight.. and whilst the high cylinder pressure causes the gas to go one way.. the very low (relatively)15 psi dosnt cause the water to go the other way.. its all very simple and logical once u know what happens.. also this leak only occurs under heavy load at first not when the engine is idleing so looking at caps to find the slight hiss as the gas gets out (over 15 psi gets out under 15 psi stays in) will not do much good..

what u decribe is exactly the same problem but further down the line.. ie.. a bigger leak.. right at the beginning it does exactly as i describe.. go even further down the leak proccess road and the water will get drawn into the cylinder all the time and the rough running will never go away.. in fact a hydraulic lock will occur the next time the car is started..

basically dude we are talking exactly the same problem.. just the various stages it takes.. stage one is how i describe.. stage two is how u describe.. stage three is the actual gasket blow with water in there all the time and a car that cant be run.. stage four is off with its head.. he he

stage one is not normally considered a problem by the way.. but it happens.. its just that folks arnt aware of it.. i am trying to make them aware of it.. so i stick to my original (it was me by the way) statement.. pressure in the system when the car is cold and has been stood overnight is the first signs of head gasket failure.. which of course mustnt be confused with the second or third stages of head gasket failure.. he he

not knowing about stage one is the problem by the way.. cos the system is not meant to have a constant 15 psi in it all the time.. stage one must have sold more water pumps.. hoses.. radiators.. u name it.. as folks desperately try and fix all the leaks and other mysterious symptoms that keep popping up..

that cap blow off point of 15 psi by the way is an emergency pressure release... under normal conditions the pressure would only get that high if the temp gauge was in the red and the car well over heated..

trog100



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