My oil pressure line is clear and I can see the line is not completely filled with oil. (Checked when running)
Rice Killer said:when my motor is warmed up my oil pressure reads just a hair over 0 at idle but at 2500 rpm (for instance) it reads over 50psi.
Is it ok to run like this?
Air is more compressable than oil is correct but once the pressure stabilizes it will read correctly even with air in the line. It will be slower to reachJeffblk72 said:. Air is far more compressible than oil. Bubbles will throw it off. Burp the line and see if it helps.
Pressure is pressure in a dial guage.You are not compressing the oil nor the air,(compressing liquid would be an ugly situation,if possible at all).wskaiser said:Air is more compressable than oil is correct but once the pressure stabilizes it will read correctly even with air in the line. It will be slower to reach
pressure and will show pressure longer when the engine is shut off until the air pressure bleeds off but the end result is the gauge will read correctly under operating conditions even with air in the lines.
You have described in better words what I was trying to say but I still say the air in the line is compressed equal to the oil pressure in the line. That is why the gauge response is delayed if there are air bubbles. It takes a while to compress the air on startup and a while for the pressure to bleed off at shutdown, short as it may be.keithsixty3 said:Pressure is pressure in a dial guage.You are not compressing the oil nor the air,(compressing liquid would be an ugly situation,if possible at all).
novaboy009 said:I had to switch over my mega-mile, beat to death, almost impossible to kill 307 to 50W20. It read 0 psi at idle after getting off the highway or driving at a constant rpm for awhile. With the thick oil I have about 15-20 psi at idle. All better.
I have had a similar experience. I built a mild bracket engine with very loose bearing clearances (.0035 rods and .004 mains). I was making use of some parts that were worn and since I was building it for myself I knew there would be no panic or complaints. It was fine on the dragstrip since the engine was started cool and then cooled off after ever run. I eventually put the engine in a street car and had 5 psi oil pressure at idle and 30 psi at 2500 rpm when the car had warmed up to 180 degrees. This was with 10-40 oil. The engine also had a standard oil pump and did not have a high pressure spring. I changed the oil to 4 quarts 20-50 and one quart Lucas. The idle oil pressure went to 22 lbs and the driving speed pressure was 45-50 at 2500-2800. I knew nothing was wrong with the engine except being to loose in the bearing clearances. I put almost 5000 trouble free miles on it before I changed it out to another engine. If you have cut your filter apart and did not find metal particles and residue the oil change is the cheapest and simpliest way to increase pressure. I DO NOT WANT TO TELL YOU TO DO THIS AND THEN SOMETHING BREAKS AND BLOWS UP BECAUSE OF MECHANICAL PROBLEMS. DO THIS ONLY IF YOU THINK THERE IS NO MECHANICAL DAMAGE IN YOUR ENGINE.
Pressure is pressure period.Your statement about compressing oil and air was inaccurate.Even in hydraulics arent you pumping the fluid to increase the pressure.Liquid+compression,nasty.I know all about needle fluctuation,I work with it every day.Speaking of hydraulics,we have recently switched over to a synthetic oil that resists those evil temptations of boiling.It also has an increased run life,probably costs triple the amount of the organic based oils.Jeffblk72 said:In the low pressure world of cars, I'll give you the guage pressure is just that, but air will tend to take up fluctuations (needle twitch). In the area of thermodynamics, I wouldn't stick my neck out and make a statement like that. Sorry, my b.s. in mechanical engineering and FAA mechanic license are showing. As far as fluids go, I wouldn't test that pressure is pressure regardless of medium idea with brake fluid. You'd be suprised how hydraulic fluid boils in a mini cup car or aircraft hydraulic system with just one little biddy bubble.
Both ends of the line are fine. I dont know if the gauge is fine, "its auto gauge".Paul Wright said:If you are sure the gauge and line are fine then your bearings are probably worn out.
Have you tried a different gauge? You realy need to hook up a manual gauge to rule out your gauge or the sending unit as the culprits.Rice Killer said:So do you guys think that if I put new rod bearings and main bearings in, my pressure should be good?