Losing Oil Pressure above 4k RPM

[98yellowstang]

The 01 motor in the 98 is losing oil pressure above 4k RPMs, not completely but as the revs climb to 6k is almost down to nothing. This is under free rev or in gear. If I leave the car in gear and let off the oil pressure goes crazy, up and down and up and down as the revs decrease. Now I have concluded that its not the gauge because as the revs go up and down the valvetrain noise gets louder and quieter.

I ran full synthetic in it when I first put the motor in, then I went down to synthetic blend and now I am at pure oil and this is when the problem surfaced. I have not tried switching back to the synthetic yet.

Total miles on motor is 36k, unless the junkyard was lying about mileage.

Thoughts, concerns comments?

Thanks
Jason

 

[hotstang]

remember Ford, even with the bean counters beating them to death, spent the money on a Synthetic blend in your car from the Factory.

 

[mity2]

i have yet to tear in to 4.6, so i don't know much. But, oil pump is mechanical right?
So if that is the case, then loosing pressure at high rpm doesn't make sense. If pump is gone, then you'll have no puressure at any RPM. low or high. If your losing puressure somewhere, enough to cause this, then you'll have steady low pressure, because as pump is pumping, your losing puressure. right? So I must assume that its electrical. May be not gauge, but may be sending unit? As matter of fact, Befor I bought my GT, I test drive 00 GT, and sucker did almost identical to waht you wrote, and it turned out it just had bad connector at the sending unit...

So I would take it to your fevoret mechanic, and have them check the oil puressure using reliable gauge. Ford OEM gauge isn't exactory known for its accuracy afterall.

 

[Skud]

From dealing with the low oil-pressure problems in the ford 400 I seem to remember the following rules.

1) If oil pressure is high when cold, but low when hot. And if the pressure goes up with RPM's this it's the main bearings.

2) If oil pressure is good when cold, but low when hot. And if the pressure LOWERS with high-er RPM's then it's the rod bearings.

If I remember correctly, when the oil is hot, too much of it is seeping out of the rod ends and gets flung out as the rod spins around. The fatser the rod spins, the more oil gets past the bearing and flung away resulting in low oil pressure at high RPM.

Also, check to see if the oil is pooling in your valve covers. Maybe there is a restriction in the heads or oil passages and all the oil is getting sucked up out of the pan.

Riley

 

[98yellowstang]

Thanks for the replies.

It shows no audible signs of bottom end wear. The car has been run hard but so was the stock engine and it had 65k on it before it croaked. Maybe its just a bad motor who knows.

Later
Jason

 

[DBMSTNG]

it's the main bearings. either someone beat the piss out of the engine before you got it, or it has more miles than was advertised.

 

[98yellowstang]

Problem solved: It was a lose wire on the pressure sender.

Glad it wasn't something deeper.

Thanks to all who replied.

Later
Jason