He said 90K, do the think the mains, seals, gaskets, etc. would be wore out already and lower oil pressure this much? TallPaul and NM5K put all there examples or comparisons down on the screen pretty well, I knew where they were going w/ it, although I understood what they were talking about anyway. But 5psi. is nuts, but then agian I have a diesel 6 cly. tractor that runs 0 at idle and 20 wide open and it's been like that for 10 yrs. and it's never given any trouble, not spinning a bearing anyway. So what I'm getting at here is if you can't locate the problem, take out the gauge and hope for the best, there could always be some junk stuck right in the insert line into the motor and your engine is fine, but that's unlikely. Good luck finding out whats going on, those other 2 guys pinpointed your most likely low oil psi. causes.

Redneck-Cowboy

 

Herothc2003,i have the exact same problem as you,my oil pressure was low at idle so i put a mechanical gauge on my motor and cold my pressure is 50 lbs and when warm is around 5 lbs at idle.at highway speeds pressure is around 25 lbs. engine runs great and also has no abnormal noises doesent burn or leak oil.ive come to the conclusion that the previous owner didnt change oil often and my bearing clearances are the culpret.i just try not to let the motor idle for any length of time.i live in a rural area so thats not too hard.if i had to guess i bet thats what you have going on too.

 

I'm curious what weight oil you run. Also what is your idle, 700rpm? You may want to adjust it up to say 1000 or so to get at least 10 lbs for a measure of security.

 

I am running 20w50 right now just to see if there was any pressure difference from 10w30. I`m going to drain the oil,jack motor and trans. up, take pan, oil pump, screen,and replace pump(high volume) and clean or replace screen , if needed.That`s all I now to do right now.It will be my first time attempting, though there is a first time for every thing.Fellas I appreciate all the input @ advice and I will let you know what I find,Thanks again!!!
herothc...............

 

A good experiment about vicosity would be to get two gallon jugs, one funnel ( not a big one, just one that has an outlet about 3/8" to 1/2") 1 gallon of engine oil (straight 30w works good) , and one gallon of water. One gallon milk jugs are best becuase the pulsing of the oil and water being poured out fast represent the pulses of the oil pump spinning. Thats not really important, but keeping a realistic flow is important to the experiment ( this would not work with a 1 gallon bucket to pour from, you can easily keep the funnel full with that.)

The water represents hot oil, and the oil is the cold oil.

Take one gallon jug and put the funnel in the top. Poke one hole, not a big one, about a 1/4 inch will do, in the top of the jug just below the neck. This is so the test is not tainted by pressure from filling the jug fast, the funnel can make a seal and not allow the fluid to drain from the funnel at maximum velocity.

The funnel represents your main bearing clearances.

Now pour the gallon of water as fast as you can, steadily, trying to keep the funnel full to the brim. Have someone time you doing this. Should go very quickly and at first kinda hard to keep it full.

Next. do the same thing with the oil, have some one time you again.

You will notice that the water ( hot oil) pours much quicker (your time taken to pour the gallon of water) and was harder to keep the funnel full ( The funnel being full represents the engines ability to get oil to the top of the engine). This is what happens to a warmed up engine with large bearing clearances. The oil was easier to keep the funnel full, and took more time to do it. The difference in time between the water and the oil represents the time the oil pump had to create pressure. With all the oil passages full, the pump makes pressure. That is why you have good oil pressure at cold idle until the engine warms up.
The hot oil flows out of the bearing clearances faster, and gives no time for the engine to buld pressure or get oil to the top end.

Make any sense? Now try the same experiment with a much smaller funnel. Easier to keep the funnel full of water, isn't it!
and the time differential is about the same, but if that were an engine pumping oil, you would have 70 psi cold and 40 hot.

Hope that helps explain oil pressure and bearing clearance to you, NM5K.

 

I meant the last post for herothc2003, not for NM5K.

Sorry NM5K, said the wrong person.

herothc2003 was the one who need the training.

 

tallpaul,im running 10W30 oil.....dont have a tach yet so dont know exact on idle but seems like its about right where it should be.bought bronco for 500.00 from rancher who was selling it for his son.he said the bronc runs good(it does)but change the oil as soon as possible.ive driven that thing all summer including 3 camping trips with no probs

 

All this talk about low oil pressure got me worried b/c my fac. guage is a piece, so this Sat. I put in a mechanical I had laying around (intended for my tractor) just to see (it's clamped in my ash tray right now) and I'm running about 45 at idle and 52 running down the road and about 25 driving 15mph up a hill in 4th gear (boy I love how that 6 can do that and still pull out of it.) I am also running 10w-30. Anyway this truck has about 220K on it and it gets beat pretty hard, although I take really good care of it mantinancewise. I'm really impressed w/ the oil pressure it still has, so I'm gonna guess that you're prevouis owner didn't change oil to much because that's ridiculous.

Redneck-Cowboy

 

If you are getting 5 idle and 25 lbs at highway speed with 10w30, I would recommend a 10w40. With 5w30 I was getting 16 and 36 and so drained off two qts and replaced with 20w50 to simulate approx 10w37. Pressure is now around 19 and 43. Next I will go with 10w40 and expect slight improvement over my experimental mix. BTW I ran the weeee out of this truck one afternoon and got the oil press down to 40, a 3 lb drop. Not sure what that equates to in oil temp, but assume it got hotter and thinner.

Hows things in Rifle? Colorado and Michigan are my favorite states. I have climbed up Mt. Elbert a couple times as well as ran all the way down Pikes Peak (in my younger days). I hear the front range area from Denver on north is liberal and like a little California, but out west of the continental divide everybody is cool and has rear window rifle racks in their pickups.

 

thanks for the input tallpaul,next oilchange ill throw in some 10w40 and give her a try.i used to run 10w40 in the summer and 10w30 in the winter until i heard the thiner oil gives better mpg.took bronc in last week for new winshield and side vent window.shes in the garage now getting prepped for paint.things are good in rifle,were hoping to get some snow....been high in dry for a month now,ski areas getting nervous...

 

On thinner oil giving better mpg, see: http://www.machinerylubrication.com/...up=Maintenance