Weird Oil Pressure Gauge Readings?

[Bret]

Hey guys,

Well I noticed a weird little (maybe big) problem with my 2001 F-150 that I’d never seen before with any other vehicle I’ve ever owned.

First thing in the morning the engine’s oil pressure gauge goes to normal then drops to 0 PSI and the check oil light comes on then pops back up again and the light goes out.

It only does this for a few seconds the pops back up and continues to do this for the next two or three minutes and goes away completely when the engine is warm. Only when it's cold? Hmmmm?

Anyway I couldn’t fine any thing wrong; oil looks good and was actually changed about a week ago. I used my OBD II decoder, but no error codes shows up. Took it back to the shop where I changed the oil but they couldn’t find any problems. I would have left it with them to diagnose further, but they wanted another $100 bucks just to pop the hood, before they went any further. Being the untrusting sod that I am; I told them thanks but no thanks & drove it home without any problems.

I’m not 100% sure but I think its my oil pressure sensor is lose or defective and will try to swap that out myself before I drop any money for someone else to look at it.

Again only when she's cold? Any other ideas if the oil pressure sensor isn’t the problem?
/ubbthreads/images/graemlins/confused.gif

 

[MattP]

Check consumer reports website for recalls. I seem to remember Fords having one on the oil system about then, but I am not sure.

Good luck.

 

[mailbox]

Never heard of that problem before. This may sound DUH-HUH, but did you check the oil level? I have had that problem with the oil level low. If the crankcase is full, you need to determine if you are actually losing oil pressure. Get you a mechanical oil pressure and hook it up. This will confirm if you are actually losing oil pressure or just have a problem in the guage. What weight oil are you using? It might be too thick causing the pump to cavitate and pull air into the oiling system(it could happen). Try changing your oil and filter again with a 10w30 and see if that helps. The only other things I can think of are oil pump going out,filter defective, or the pickup screen in the sump is clogged. Well, that should get you started. Good Luck! /ubbthreads/images/graemlins/grin.gif

 

[aerog]

Is it in actual oil pressure gauge, or the on/off "gauge" that Ford had been using for awhile (such as in the Explorer, etc)? If so - then it could well be just a loose wire on the sender, or a bad sender. If it were actually a pressure drop I think you'd see more of a trend down than a sudden drop then rise again. I also have a feeling the light is part of the same circuit, just comes on when the needle drops to nothing, etc.

 

[Graham]

BE CAREFULL!!
The most likely thing to cause that type of reading is the sender unit, "BUT" I had trouble years ago like that with a Morris and it turned out to be a sticking oil pressure relief valve. When you started it, it would stick open for a few minutes then as the oil warmed up it would return to normal. I got complacent about it and didn't do anything about it, just accepting it as one of the funny things cars do, right up until it stayed open completly, starving the engine of oil presure and totaly wrecking the crankshaft.
I havn't heard of anyone else having that problem since, but if that is your problem it can be VERY expensive if you leave it too long.

I hope its only the sender.
Good luck
Graham. /ubbthreads/images/graemlins/cheers.gif

 

[Bugeye58]

Bret, is it a 302? Let me know some particulars, and I'll ask some Ford powertrain guys Saturday at our race banquet.
I wish I had known sooner, I could have asked them tonight!
Jeff

 

[Bret]

Hey,

Thanks for the suggestions everyone. The oil level is fine and according to the shop that did the servicing there is plenty of oil pressure. But alas they didn’t check it until after the engine was warmed up. So who knows.

Jeff,

The engine is the 5.4L V8. Not exactly sure what that translates over to in CI but I think it’s a little bigger than a 302.

I did talk to a couple of guys at a local shop about the problem and they seemed to be pretty confident that its just my pressure switch (sensor) that it is either flaky or it is losing contact.

Also to be safe, I’ve parked the truck until this weekend when I’d planed on doing some work on it anyway. So whatever information you guys could give between now and then I would be extremely appreciative.

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Thanks again,
Bret

 

[Aphyle]

I had something similar when I first got my MGB in the early '80's, back when you could still get replacement parts at Jaguar dealers. It turned out to be the oil pressure relief valve, which was slightly worn on one side. When replaced, the problem went away.

Cheers!