oil pressure drops under throttle!? could use some advice...

Err...it's my daily driver..Ford Ranger 4.0l V6.

factory gauge, Under heavy throttle, the oil pressure drops right off. FIne at idle but anything more than 3k and the pressure starts to drop right off. This has me kinda worried.

Engine is only 2 years old and has less than 9000 miles on it.

Changed oil/filter and pressure sending unit. no joy.
Blown mains?

Thanks for any advice you may have.

Every penny I drop into my DD is less I have to spend on my hot-rod.

 

Any noise associated with the dropoff in pressure?I would start by hooking up a known to be reliable mechanical oil pressure gauge and check it out.Could be a defective relief valve on the oil pump(I'm guessing here)but it sounds serious.

 

no noise...just a sudden drop just before 3000 RPM. No flakes in the oil (magnetic drain plug).

thanks

 

I agree with Safariknut. Hook a mech gauge and see what it is really doing. If I remember correctly we stocked a 4.0 oil pump in the inventory for just this reason.

 

Well if there is no noise associated with the drop then I would suspect the gauge.Another possibility(small)is that if you are lunging forward under hard throttle,the oil in the pan is being forced to the rear and if the pan isn't baffled properly,could cause an oil pressure drop but you would probably HEAR it before you noticed the gauge.

 

How's your oil level?

 

Just out of curiousity, what numbers are you talking about here? Idling at what? 40? and dropping to 20?

 

Haven't put a gauge on it yet, (don't own one) but I think I can borrow one.

Oil level is good, no noises. The gauge is just an idiot gauge reading low/high.

it's not a sump issue, as it it will drop even when parked and reving up the engine.

The problem is it's dropping when you give it throttle. At idle, idiot gauge reads fine.

 

i know my oil pressure is low when my oil is low.

 

Just a few thoughts;

Bad pump.
Low oil level.
Clogged pump pick-up.
Wrong filter.

 

i agree with the clogged pump theory.
if its a fresh rebuild you could have some silcone floating
when you rev it the pump turns faster which causes more suction.if your oil level is fine this might be your problem.
of course this is just a guess.

 

i just realized your in canada.
is your oil rated for cold weather?

 

what year ?replace the oilsend unit..ford has had some issues on some of the sender not reading right.mostly on start up.

 

What brand parts have you replaced with, genuine Ford? A friend had trouble with a Exploder getting hot. He replaced 2 or 3 thermostats with aftermarket ones, couldn't fix it. Finally listened to our radiator shop buddy and got a Ford thermostat and fixed it. Maybe same thing ?

 

HAven't replaced anything yet, I have a new sending unit I'll be installing tonight.

Changed the oil and filter, problem still exists.
Oil is 5 w 30 synthetic Castrol.
Engine was rebuilt 2 years ago, 9000 miles on it.

damned money pit.

I guess I'd better find somebody with a mechanical gauge and check it out. Engine needs to come out for the pan to drop to change the pump. A BIG FRIGGIN HASSLE. Somebody stole my engine crane and I will be doing the job oustside in the snow.

thanks for the help folks!!!

 

Trying some thicker oil (just as a test) might help you eliminate some possible problems- if it's a bad pump, the thicker oil would probably improve your oil pressure, and you'd know that was it. But if it's a clogged pick-up screen or something jammed in the relief valve, the viscocity won't make a big difference. If you've got decent pressure at idle (20 psi warmed up) it's doubtful that it's bearings.

 

My guess is the pressure relief spring has gone south, and and is opening when the pressure rises above 30psi. I'm not familar with that particular oil pump, but I had the same problem on a 283, I just swapped out the pump. KK

 

Faulty Oil pressure sensor.

$8 part and 10 minutes to replace.

WHEW!

Thanks for you help folks, this is why I love the H.A.M.B!