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Ford 9N, 2N & 8N Discussion Board

Re: Hot Weather and Oil Pressure

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Posted by TheOldHokie on September 02, 2013 at 12:49:12 from (

In Reply to: Hot Weather and Oil Pressure posted by RumT on September 02, 2013 at 12:11:35:

Quoting Removed, click Modern View to see

I am not in the least closed minded and I am not upset - perhaps we are simply failing to understand each other. I've read your responses and I see no answer to my last question. I spent a fair part of my professional career reading and writing technical specifications so I'm pretty good at deciphering them. I understood your earlier explanation of how a malfunctioning (i.e. a weak or leaking valve might produce a higher pressure when cold and lower pressure when hot. A very delicate balancing act and while I agree it is possible I must believe it actually manifests extremely rarely. Obviously if you are experiencing low oil pressure issues cleaning and checking the valve to make sure it is in fact seating properly and has a significant cracking pressure (.e.g spring tension) is appropriate. So let me rephrase my last question and make it more explicit and perhaps we can get back on the same track:

If the system oil pressure is 30 PSI at cold startup and 10 PSI at hot idle and the cracking pressure of the valve is 50 PSI (e.g. worn engine) will increasing the cracking pressure to 60 PSI increase the system oil pressure?

And the corollary: if you reduce the cracking pressure of the valve to 30 PSI will it reduce the cold or hot oil pressure in this engine?

The answer should be clear- increasing or decreasing the cracking pressure does nothing because as long as the cracking pressure is 30 PSI or greater at no time is the valve ever off it's seat. Cold or hot the pump is simply unable to produce enough flow into the engine to create more than 30 PSI of back pressure in the supply line. This is almost universally the situation in N-series (and most other) automotive engines experiencing low oil pressure readings.



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