Author Topic: low oil pressure  (Read 9517 times)

mustangluver

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low oil pressure
« on: April 27, 2010, 12:49:00 PM »
on my 66, while warming up, it stays between like 25-like 50 and after it warms up and gets over like 180/190 it suddenly drops to like 10-25. ive been told it can be my sending unit or my oil pump,  but want a few opinions to be sure. please note that i did a oil change not long ago.

Tim175

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Re: low oil pressure
« Reply #1 on: April 27, 2010, 12:52:42 PM »
Try replacing your oil pressure sending unit first. Also what type fof sending unit/gauge are you using? What oil are you running?

Soaring

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Re: low oil pressure
« Reply #2 on: April 27, 2010, 04:23:36 PM »
A sending unit either sends or it doesn't.  They are cheap though, so go ahead and replace it along with a factory oil pump. 

mustangluver

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Re: low oil pressure
« Reply #3 on: April 28, 2010, 01:44:31 AM »
my gauge i believe is an aftermarket sunco gauge. my oil is a all season grade if i remember right its castrol 5w-30 high mileage full synthetic. is the oil pump fairly easy to replace and how long would it take? i dont always have alot of time to spend with the car.

Soaring

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Re: low oil pressure
« Reply #4 on: April 28, 2010, 02:24:11 AM »
It will take a couple of hours to replace the oil pump.  You have to remove the oil pan to get to it. 

6mustang6

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Re: low oil pressure
« Reply #5 on: April 28, 2010, 05:47:58 AM »
Ok, we all got to remember that a oil pump doesnt pump pressure but volume. The oil being pushed through the bearings creates the pressure. If your bearings are worn then you are going to have low oil pressure espiacally when its warm. It all honestly every ford i have has low oil pressure at idle when they are warm. Throwing a new oil pump on your engine is unlikely to help any. I swear to you that my 352 in my truck when warmed up and idling has less then 10 psi!! but it doesnt make a noise. Just deal with it i say as long as you are getting oil up to your rockers and they arent making any noise, then you should be getting oil to all your bearings.

66GTKFB

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Re: low oil pressure
« Reply #6 on: April 28, 2010, 10:12:00 AM »
There is an oil pressure relief valve built into the oil pump. It is the means to keep oil pressure from getting to high and is, as all mechanical things, subject to failure. It is supposed to "dump" oil over 50 to 80 lbs by use of a spring. It also gets stuck. As it is not serviced, you need to replace the oil pump.
Jim

Jeff73Mach1

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Re: low oil pressure
« Reply #7 on: April 28, 2010, 01:59:50 PM »
First gauges are inaccurate!  Verify the actual numbers with a mechanical gauge.

IMHO That is a thin oil for that engine.  You might go to a heavier weight to see if that keeps the pressure a bit higher when warm.

Most likely you have worn main bearings-at least to some extent and the oil pressure is dropping because the oil has excessive space to travel through and can't create back pressure.

if something in the neighborhood of a 15W40 can't keep your pressure at a true15 pounds at idle, you are likely looking at a rebuild.

rule of thumb is a minimum of 10 PSI for every 1000 rpm the engine turns.

so at 2500 rpm, you really should have 25 psi at a minimum and at 5500 rpm 50psi is only okay.

If pressure was good and this is a new development, it could be a sensor or a gauge, but it could also be spun main bearings.

I spun the main bearings in a boat motor last summer and heard a change in the engine note under full throttle before the gauge even registered the drop in oil pressure.  I couldn't explain what I heard to anyone else in the boat, just that it had changed and sure enough I throttled down and the oil pressure dropped to virtually nothing.

I think you just have some wear and too thin of an oil.  5W-30 is designed for modern high tolerance engines.  A 10W-30 or 10-40 or 15-40 will be more appropriate for old iron v-8's, especially with some miles on them.

mustangluver

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Re: low oil pressure
« Reply #8 on: April 28, 2010, 02:19:23 PM »
I know i can test the sensor. but no idea where i can go get the tool. and ill be changing the oil out later on next month anyway  :)

mustang245

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Re: low oil pressure
« Reply #9 on: April 28, 2010, 11:35:30 PM »
easiest way to test the sensor would be to get a scan tool. try any tool manufacter or try ebay. you should be able to find one

mustangluver

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Re: low oil pressure
« Reply #10 on: April 29, 2010, 01:42:41 PM »
mustang245,
you do realize that a scan tool isnt for a 60s mustang right? if they make one for a 43 yr old car please share with the rest of us.

6mustang6

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Re: low oil pressure
« Reply #11 on: April 30, 2010, 08:28:45 AM »
???? Im hoping he is talking about a multimeter. lol

mustang245

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Re: low oil pressure
« Reply #12 on: April 30, 2010, 01:22:29 PM »
Sorry, forgot this was a classic mustang. A multimeter will help determine if you are getting voltage to the sensor, or if there is a break in the circuit. I would replace both sending unit and pump

mustangluver

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Re: low oil pressure
« Reply #13 on: May 04, 2010, 02:02:42 AM »
oh boy  8) lol theres voltage running to it seeing as how the needle moves.   

Soaring

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Re: low oil pressure
« Reply #14 on: May 04, 2010, 03:18:29 AM »
Then you are in luck.  Replace the sending unit 

mustangluver

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Re: low oil pressure
« Reply #15 on: May 04, 2010, 11:59:58 AM »
last time you responded you said it was my oil pump. ill go ahead n replace the sending unit first though. correct me if im wrong but i need a special socket dont i?

66GTKFB

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Re: low oil pressure
« Reply #16 on: May 04, 2010, 01:57:16 PM »
No.

mustangluver

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Re: low oil pressure
« Reply #17 on: May 06, 2010, 01:44:43 AM »
that has got to be the shortest reply i have ever seen on here haha. before i do the repair imma get a mechanical gauge and do a direct check on the oil pressure.

 

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