no oil press after hot or idling 4.0 auto

[92dangaranga]

My 92 Ford Ranger has just started to loose oil pressure after it gets hot, but only looses it when i come to a complete stop and it is leaking around rear seal and valve covers but its been leaking a little since i got it, i have not had a problem with this truck since i got it a year ago now all of a sudden its blowing oil. ive been told it could be the screen but ive also been told i would have to pull motor to clean that

 

[RonD]

First, when warm and idling are you now hearing the lifters/rockers(valve train) "ticking" if not then pressure is below 6psi(0 on gauge) but above 4psi.

Oil gets thinner when it is warm, it is normal to have less pressure in warmed up engine, but not below 6psi

Rear main seal can be repaired, but transmission needs to come out, flywheel(manual) or flexplate(automatic) is removed and rear main seal can be replaced, cheap part but hard to get to.
Failed rear main seal can pump out oil quite fast

Valve cover leaks are not pressure leaks, but you do loose oil so best to fix the leaks.
The stamped metal valve covers bend if over tightened, so after they are off make sure to straighten the flat metal rim that clamps down on the gasket, or it will just start leaking again.
And snug down the bolts, don't crank on them, lol.
Use cork gasket, it seals better, rubber gaskets are used if you will be pulling of valve covers fairly often, they can be reused, cork can't be(shouldn't be).
Cork swells with age and contact with oil on the inside

You can also use spreaders or "clamps", they go under the valve cover bolts and spread the clamping force over a wider area, but a good straight valve cover will be fine without them.

Make sure PCV system is working correctly it keeps a slight negative pressure in the valve covers and oil pan, so keeps oil from seeping out, but once it starts it will keep leaking

 

[92dangaranga]

Thank you for the information. The truck only looses oil pressure at low rpm like when im stopped. The gauge will go as far down as possible as if there werent any pressure at all but as soon as i give it gas it comes back up to normal. its rather confusing

 

[alwaysFlOoReD]

The oil pump is directly related to rpm. The higher the rpm, the higher the oil pressure, to a point because there is a pressure relief valve to prevent too high pressure. If the motor is old then bearings are worn and oil leaks past them easier leading to low or no oil pressure at low rpm.

Sent from my XT1032 using Tapatalk

 

[RonD]

Thank you for the information. The truck only looses oil pressure at low rpm like when im stopped. The gauge will go as far down as possible as if there werent any pressure at all but as soon as i give it gas it comes back up to normal. its rather confusing

Do you hear "ticking" from the valve train at idle that isn't there at higher RPM?

 

[enjr44]

Thank you for the information. The truck only looses oil pressure at low rpm like when im stopped. The gauge will go as far down as possible as if there werent any pressure at all but as soon as i give it gas it comes back up to normal. its rather confusing

That is because it is not a gauge. It is a switch connected to the needle (like the oil pressure light in many vehicles). Above 6 psi it reads normal. Below 6 psi it reads zero. Ford figures that if you have 6 psi you are good to go and there is no reason to tell you more. And by the by, back in the 50's many Fords had zero oil pressure at idle and they lasted for years that way.

If it were mine, and before I had a heart attack, I would change the oil pressure sending unit on the engine (they are cheap). They don't fail often; but, ......... It sounds to me like a high mileage engine that is just starting to get tired. And with the pressure gauge, not being a gauge it just showed up.

If it isn't the sending unit, I would put a heaver oil in it. Maybe something like 10w40 or 20w40 rather than the 10w30 it calls for. The 40w will maintain oil pressure a little better when hot. Someday, the engine is going to have to come out and be rebuilt; but, with care that could be several years (or, maybe tomorrow, who knows!!). Done right, after the rebuild,it will be ready for another 200K.