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oil pressure question

 
  #1  
Old 07-17-2008, 12:54 AM
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oil pressure question

oil gauge is slowly moving to the low side of normal,checked the oil level it's good what could it be, why is the going down?
 
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Old 07-17-2008, 04:35 AM
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What year truck?
 
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Old 07-17-2008, 02:54 PM
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Hook up a mechanical gauge and read off of that. The stock gauges merely "ballpark" actual conditions. I wouldn't put too much trust into what those say.
 
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Old 07-17-2008, 03:05 PM
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Factory gauge is a glorified warning lamp. It's either on (normal) above 6psi or off (red zone) under that.

Hook up a mechanical gauge and get a real reading. These senders and elec gauges are known for being unreliable.
 
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Old 07-17-2008, 04:19 PM
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It depends on the year. Somewhere around 89 is when Ford switched (no pun intended) to the "idiot gauge" oil pressure display. My 87 has a variable resistance sender and variable gauge from the factory.
 
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Old 07-18-2008, 12:35 AM
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sorry 91 F250 i've had the truck for two years now always on the "R" since i got it now it go's past the "N" seams ok on the way home from work(night time) but on the way in gets me wondering. i'll do the mech gauge and see what i get should have one out in the shed. thanks guys.
 
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Old 07-18-2008, 04:41 AM
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Your truck should have the oil pressure switch. If the gauge is not dropping all the way to zero, there may be a bad connection between the oil pressure switch and the gauge, or possibly a problem with the gauge itself. You are on the right track in checking with a mechanical gauge.
 
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Old 07-18-2008, 02:28 PM
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I have a simular issue,
mine did exactly what yours is doing, except today the needle bottomed out.
It fluctuates from normal to zero. Truck seems to run fine with no signs of oil starvation.
 
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Old 07-18-2008, 04:35 PM
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hook up a mechanical gauge to get a proper reading.
 
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Old 07-18-2008, 05:22 PM
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You can't always rely on the engine to make noise or act strange when you loose oil pressure. I drove a '96 E250 with 351 that had a flickering oil pressure gage, but ran nice and quiet. I hooked up a mechanical gage and it had 7psi from idle to 3000rpm The main and rod bearings were worn out. The customer declined repairs and drove it for a while before it started knocking. The 1990 truck in my signature has a bad cam bearing and reads 0psi at any rpm once it warms up, and has run nice and quiet for the past 1000 miles. Its been kind of an experiment of mine to see how long it will last.
 
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Old 07-22-2008, 06:48 AM
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if a oil pump started to fail, would it not be either a steady decline in pressure or a sudden permanent loss. I do agree the best way to find out is a mechanical guage.
By the way, is there an easier way to get to the pump without almost pulling the engine?
 
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Old 07-22-2008, 09:10 AM
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clogged pickup screen is the most likely suspect.
 
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Old 07-22-2008, 04:29 PM
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A clogged pickup would show itself at higher rpms where oil flow rate demand increases, not so much at idle. I didn't see if there was any mention as to when the oil pressure gauge/light would flicker, but just wanted to point this out before anyone jumped to conclusions.
 
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Old 07-22-2008, 05:16 PM
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a clogged screen will show at other times other then high rpms.
 
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Old 07-22-2008, 07:49 PM
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i have a guage on the dash,
the irratic movement is very random. i first noticed it on the highway.
it does it at idle and city speeds. i picked up a new pressure switch for 15 bucks. ill try that first. im having a hard time finding a mechanical guage around here.
something to be noted here. when it fluctuates, it goes from middle to maxxing out to the left. I just replaced the oil pan 6 months ago. screen on pump was clean then.
 

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