Oil pressure drop again!!

[03blackmerc]

hey hey back again with some same questions. about a year ago now i was sitting in the car wash with the MM in drive. i noticed the oil pressure sittin at 25psi at idle. it always usually sits around 72psi always no matter if its in drive or whatever. i thought the problem just went away on its own. only that one day i saw it drop to 25psi, but never again. then today after about an hour and a half drive i noticed the oil pressure droppping again to 25psi only at idle with it in drive or reverse. so the drop is only occuring when the motor is at idle with a load. driving, and idling in park or nuetral the pressure iis right up to 72-75PSI. ive heard many times that this gage is a fake dummy gage. what would cause this drop. im using motorcraft synthetic 5w-20 oil which is recomennded. i got about 120k on the clock now, do you think this is caused from just engine wear?

[RR|Suki]

hey hey back again with some same questions. about a year ago now i was sitting in the car wash with the MM in drive. i noticed the oil pressure sittin at 25psi at idle. it always usually sits around 72psi always no matter if its in drive or whatever. i thought the problem just went away on its own. only that one day i saw it drop to 25psi, but never again. then today after about an hour and a half drive i noticed the oil pressure droppping again to 25psi only at idle with it in drive or reverse. so the drop is only occuring when the motor is at idle with a load. driving, and idling in park or nuetral the pressure iis right up to 72-75PSI. ive heard many times that this gage is a fake dummy gage. what would cause this drop. im using motorcraft synthetic 5w-20 oil which is recomennded. i got about 120k on the clock now, do you think this is caused from just engine wear?

You don't have 70 odd psi at idle with a warm motor anyway, and as a general matter at idle the psi will go down vs driving around being on the freeway etc. The gauge is "fake" if you have the stock one, and I'd guess either it's going bad or the sender is acting up.

[cougar9150]

Don't quote me on this but I think I remember seeing someone mention that if the stock gauge actually gets down that low the pressure is actually closer to 5-10psi inside of the motor.

I know w/my working auto meter gauge I run around 75 psi when cold at idle, once it warms up I get around 70-75 psi when I am pushing on it, 45-50 psi when cruising, and 20-25 psi when at idle (I hate short sweep gauges).

I think if your stock gauge is actually reading that low you may have another issue and are possibly loosing pressure somewhere. What it could be I am not 100% sure but with the age of your motor and depending on how anally it was maintained it might just be about time to to get her freshened up.

I would also see if a member who still has their stock sending unit and gauge around might be willing to sell or give it to you. It may just be an erroneous signal from your stock unit. I would check this prior to moving on to anything major. My above statement is because I'm used to expecting the worst and finding it to be true.

The best bet would be just to swap in a real gauge and verify what the actual pressure is. This has always been one of the first mods on any of my cars just because I don't trust idiot lights to warn me before it is already to late.

[fastblackmerc]

Real oil pressure gauge and running 5w30 or 5w20 at idle I get over 120psi when cold and 25psi when hot. Just like it should be.

Sounds like your sender or gauge maybe on the way out. Could also be a bad / loose connection at the sender or gauge. The way the stock system works, as long as there is oil pressure at the sender it will read 65 - 75 psi. As stated before it's a dummy gauge.

[Blackened300a]

Real oil pressure gauge and running 5w30 or 5w20 at idle I get over 120psi when cold and 25psi when hot. Just like it should be.

Sounds like your sender or gauge maybe on the way out. Could also be a bad / loose connection at the sender or gauge. The way the stock system works, as long as there is oil pressure at the sender it will read 65 - 75 psi. As stated before it's a dummy gauge.

+1 I have the real gauge and it shows 22-25psi on a warm engine and about 100psi on a cold start. Normal driving I pull around 55-75psi. The stock gauge was always at 60psi.

[RF Overlord]

03blackmerc, it's a very simple system with 3 pieces:

1) a switch that closes when there's more than ~6 lbs of pressure
2) a wire that connects directly from the switch to the gauge
3) and the fake gauge itself.

The gauge reading will never change, regardless of the oil you use or the miles on your motor, or the gear you're in, unless the true pressure gets below ~6 lbs, then the gauge will read zero. If your reading EVER changes, then one of those three pieces is the culprit. Do yourself a huge favour and get rid of the useless fake setup and install a real working gauge.

[Blown3.8]

03blackmerc, it's a very simple system with 3 pieces:

1) a switch that closes when there's more than ~6 lbs of pressure
2) a wire that connects directly from the switch to the gauge
3) and the fake gauge itself.

The gauge reading will never change, regardless of the oil you use or the miles on your motor, or the gear you're in, unless the true pressure gets below ~6 lbs, then the gauge will read zero. If your reading EVER changes, then one of those three pieces is the culprit. Do yourself a huge favour and get rid of the useless fake setup and install a real working gauge.

What he said. And its prolly the sending unit that is acting up.