Hot Weather and Oil Pressure

A couple of weeks ago I posted that my OP was low and had lost prime at start up.

This morning was finally cool, when I started EvelyN 48, the OP was up around 30 at idle. That is what I had before and I am not concerned any more.

I know my O. Pump is less than perfect. I have only about 5 lbs when really hot idle. It has been that way for years.

We had a couple of months mostly in the 90s. The N sat for about a month and lost it prime. Using 10-40 fwiw.

(quoted from post at 19:12:15 08/21/13) A couple of weeks ago I posted that my OP was low and had lost prime at start up.

This morning was finally cool, when I started EvelyN 48, the OP was up around 30 at idle. That is what I had before and I am not concerned any more.

I know my O. Pump is less than perfect. I have only about 5 lbs when really hot idle. It has been that way for years.

We had a couple of months mostly in the 90s. The N sat for about a month and lost it prime. Using 10-40 fwiw.

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Lost prime is a wear issue. If you can start it and get pressure by manually priming just be prepared to take the extra step of priming it. The problem won't get better with time and an oil pump rebuild is cheaper than an engine overhaul. The last pump I got appeared to be toast but a new set of gears made it like "new". Your problem is not the grade of oil you are using - it is a worn oil pump.

TOH

Thanks! I will be watching the OP gauge. So far the loss of prime is a one time thing, which I partially attribute to heat and time.

Hey OH!!! is that the OP you had the big speeal about the teeth wear on and on and at the end you said to my reply "well it should be obvious what's wrong" Now lets be fair I was right! right? LOL.Yall never admit to it will ya? LB master of the obvious.

(quoted from post at 16:20:32 08/22/13) Hey OH!!! is that the OP you had the big speeal about the teeth wear on and on and at the end you said to my reply "well it should be obvious what's wrong" Now lets be fair I was right! right? LOL.Yall never admit to it will ya? LB master of the obvious.

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Actually Sir Master you clearly missed the obvious. Despite your doubts it was obvious what was wrong from my description and the pics I posted. The good news is the wear on the housing was minimal and all new gears, a new shaft bushing accurately reamed, and resurfacing the cover fixed it. It bench tested 150 PSI @ 500 RPM into a 1/2" discharge using SAE 10W30 oil at 75F with plenty of flow. I come from the world of science and engineering and I try not to guess or speculate - I measure. Now educate me again about how engine oil never wears out and it's all a big sales conspiracy - I'm still having trouble with that little bit of "obvious" back yard physical chemistry....

TOH

Science and engineering, Oh ya those were the guys who sat in an AC office and told us grunts how to put wrecked aircraft back together and why with out them an their neat papers with the fancy numbers on them it could not be done and the food chain would be broken. Don't forget all the science and engineering that went into the Titanic, now those were some real educated science fokkkk and engineers. Who designed that mess, water tight doors thats great and bulkheads that failed to go all the way to the overhead DAAAAA. My favorite sell job other then the 3K oil change scam was the thing on stage 34 in Hollywood the moon landing Ya right what a public scam that was.I have a challenge for TOH find 5 qts of used oil that has been sheared and all the other things you say can go wrong and has LOST its ability to lubricate, I will put it in one of my 100K or 200K motors and run it. Ill buy you a drum of your favorite oil and filters to go with it if my motor takes a seize. one thing to make this a fair deal, you can not produce something that does not exist outside the hidden laboratories where all that stuff is discovered.I cannot believe you real buy into oil change scam.

(quoted from post at 01:45:15 08/24/13) Science and engineering, Oh ya those were the guys who sat in an AC office and told us grunts how to put wrecked aircraft back together and why with out them an their neat papers with the fancy numbers on them it could not be done and the food chain would be broken. Don't forget all the science and engineering that went into the Titanic, now those were some real educated science fokkkk and engineers. Who designed that mess, water tight doors thats great and bulkheads that failed to go all the way to the overhead DAAAAA. My favorite sell job other then the 3K oil change scam was the thing on stage 34 in Hollywood the moon landing Ya right what a public scam that was.I have a challenge for TOH find 5 qts of used oil that has been sheared and all the other things you say can go wrong and has LOST its ability to lubricate, I will put it in one of my 100K or 200K motors and run it. Ill buy you a drum of your favorite oil and filters to go with it if my motor takes a seize. one thing to make this a fair deal, you can not produce something that does not exist outside the hidden laboratories where all that stuff is discovered.I cannot believe you real buy into oil change scam.

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Wow - every time I think it can't get any worse you prove me wrong
It seems that if you want to know the real truth you just ask L.B - "master of the obvious".
So far boys and girls L.B. has taught me that:

• [*:dafd50bb37]Chemistry, physics, mathematics and engineering in general is just a bunch of worthless drivel put together by lazy mindless incompetents who don't know what they are doing and never really worked a day in their lives.[*:dafd50bb37]Their research is really just propaganda commissioned in support of corporate conspiracies designed to bilk the real grunt working men of their hard earned dollars.[*:dafd50bb37]Engine oil never loses it's lubricating properties and consequently there is no need to replace the oil in an internal combustion engine[*:dafd50bb37]Man never landed on the moon.[/list:dafd50bb37] Tomorrow's lesson: The international space station is just a plastic model in a studio somewhere and the earth is really flat????
  
  TOH
  
  
  

With ambient temps like that I would seriously be considering a heavier/straight wt oil...hd30.

Perhaps the next step would be to check the pressure relief valve spring for serviceability. Or just add washer(s) behind it. I am up to using straight 40W and max hot pressure is at 12 psi. I cant pull back to idle hot, the pressure will drop off.

(quoted from post at 10:59:35 09/02/13) Perhaps the next step would be to check the pressure relief valve spring for serviceability. Or just add washer(s) behind it. I am up to using straight 40W and max hot pressure is at 12 psi. I cant pull back to idle hot, the pressure will drop off.

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Please explain to me how a spring that maintains 30 PSI at startup suddenly can't maintain 10 PSI when the engine warms up.

TOH

The spring could be weak and allowing oil to bypass all the time. You could have 30 psi at start up, due to cold oil viscosity, even with the plunger off the seat. Oil reaches operating temperature and pressure drops.

(quoted from post at 12:51:13 09/02/13) The spring could be weak and allowing oil to bypass all the time. You could have 30 psi at start up, due to cold oil viscosity, even with the plunger off the seat. Oil reaches operating temperature and pressure drops.

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Possible but incredibly unlikely IMO. I'll hazard a guess that over 99.9999% of the times that an engine exhibits these symptoms it is because the engine is worn and internal oil clearances, including the pump itself, have opened up. In fact the only advantage of the oil pressure gauge versus a light is as an an indirect measure of internal clearances. When new TOOH's Cadillac Catera pegged the gauge at 80 PSI when cold and made 60 PSI at road speed on a blisterrng hot summer day. Now it still pegs the gage when cold but only makes about 45 PSI when hot. At 150K miles I'm quite sure that is a sign of bearing wear not a leaking oil pressure relief valve.

TOH

Seen this and dealt with it in aviation engines that had no adjustable PRV. You shim them with washers to make adjustment. Clearances open over time. Add AN960 washers/"shims" to increase spring pressure.

You sound like an engineer. Perhaps?

(quoted from post at 13:46:29 09/02/13) Seen this and dealt with it in aviation engines that had no adjustable PRV. You shim them with washers to make adjustment. Clearances open over time. Add AN960 washers/"shims" to increase spring pressure.

You sound like an engineer. Perhaps?

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Nope - not an engineer but I've worked with many. If you read the archives you'll quickly discover this topic is one of my pet peeves.

One more time - how does increasing the cracking pressure on ANY pressure relief valve increase a system pressure that is below that cracking pressure?

TOH

(quoted from post at 11:16:08 09/02/13)

(quoted from post at 13:46:29 09/02/13) Seen this and dealt with it in aviation engines that had no adjustable PRV. You shim them with washers to make adjustment. Clearances open over time. Add AN960 washers/"shims" to increase spring pressure.

You sound like an engineer. Perhaps?

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Nope - not an engineer but I've worked with many. If you read the archives you'll quickly discover this topic is one of my pet peeves.

One more time - how does increasing the cracking pressure on ANY pressure relief valve increase a system pressure that is below that cracking pressure?

TOH

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Yes, you do seem upset by this thread, but it is good you are admitting to your problem. The answer was in my first post on this thread. You ask that I explain this to you. This is only feasable if you are receptive and open. I feel that you are closed minded to this subject and, accordingly, not receptive. The simple answer is there. It's up to you whether you are capable of finding it or not.

(quoted from post at 15:11:35 09/02/13)

(quoted from post at 11:16:08 09/02/13)

(quoted from post at 13:46:29 09/02/13) Seen this and dealt with it in aviation engines that had no adjustable PRV. You shim them with washers to make adjustment. Clearances open over time. Add AN960 washers/"shims" to increase spring pressure.

You sound like an engineer. Perhaps?

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Nope - not an engineer but I've worked with many. If you read the archives you'll quickly discover this topic is one of my pet peeves.

One more time - how does increasing the cracking pressure on ANY pressure relief valve increase a system pressure that is below that cracking pressure?

TOH

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Yes, you do seem upset by this thread, but it is good you are admitting to your problem. The answer was in my first post on this thread. You ask that I explain this to you. This is only feasable if you are receptive and open. I feel that you are closed minded to this subject and, accordingly, not receptive. The simple answer is there. It's up to you whether you are capable of finding it or not.

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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 [u:8b7b05643a]might[/u:8b7b05643a] 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.

TOH