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I checked the oil and noticed a little (not much at all, just enough to dilute) water in the oil. The first couple of times at fire up, the oil pressure would read 55psi and go down to 45 at idle, but now is showing 30-35psi at idle. Will water cause that much of a pressure drop? I am currently running a 10-40 as this engine has new bearings, but am ready to go to 20-50. It has about 6 hours on the new bearings.
Are you talking like a few drops of water? If just a few drops it may just be condensation. I would change the oil and run it but keep a close eye on it.
check that timing cover..seems to be a common cause.
When you say "noticed" do you mean at the top of the valve covers or on the dipstick? That can be important. If on dipstick then checking the source makes sense. If on top of valve covers only, can be from evaporation and may not be a problem.
45 idle psi versus 30-35 psi is significant, but oil pressure strongly depends on temperature, and that difference is only meaningful if the oil temp was identical for both tests. Was the 45 after a short run and the 35 after some long hard runs? Same day? Were lake and air temps the same? Without knowing oil temperature for both readings it's hard to say if the difference you recorded means trouble.
About the water caused pressure drop question...oil pressure also depends a lot on viscosity, as you suggested with the change to 20-50. But water in oil, forming an emulsified liquid, actually increases viscosity in many cases I believe. Just working from memory here so take it for what it's worth http://free.***boat.net/ubb/smile.gif
And with only 6 hours on bearings, loosening clearances may not be a big factor, unless maybe you redlined it all 6 hours?
So my guess is the drop in idle pressure may be temperature related...so make sure you rule that out during your trouble-shooting.
Good luck,
jer
[This message has been edited by LVjetboy (edited March 17, 2002).]
Actually, I have a draincock installed on the side of my oil pan and just emptied a little into a clear container and checked it out. I was looking for bearing material to make sure that wasn't the problem and found a little water in there.