79 f150 oil pressure issues

[xkotyx]

when i start my f150, the oil pressure is fine (alittle low but nothing to worry about). well as it warms up the oil pressure slowly drops until it reads no pressure. there isnt any serious oil leaks or anything and the oil is at the proper lever.

any suggestions?

 

[robertc1024]

I'd get a mechanical pressure gauge and double check. No oil pressure = blown engine.

 

[xkotyx]

I'd get a mechanical pressure gauge and double check. No oil pressure = blown engine.

yeah. its bugging me how it starts out fine for about 5 to 10 min though! good thing i havent been driving it. tryna get it running good before i take it out.

any suggestions on the possible cause?

 

[robertc1024]

How many miles? If it's really dropping to near nothing, you've got a bad oil pump or seriously wasted bearings. I would think you could hear that though.

 

[xkotyx]

its around 130k maybe 140k? cant remember exactly. and it sounds fine when it runs. thats what made me think its maybe a sensor.

i left for about 10min to let everything move around, came back and looked around the outside and stuff. then i look in the cab and its not reading, so i shut it off. its not really leaking, other than a few drips where it needs a new drain plug... which i doubt that would cause any oil pressure issues

 

[snake]

How old is the oil? It may be broken down and that would cause this. Also, smell the oil on the stick and see if it smells like gas or some other contaminant that could have gotten in and thinned it out. Most likely a sending unit though, if the oil pressure was that low you would hear the engine start ticking (first) then knocking, then boom.

 

[kimcrwbr1]

Take the wire on the pressure sender and when the pressure drops pull the wire off the sender and touch it to ground while someone is looking at the guage. If it reads high pressure it is either the sender, pump or engine. Have you changed the oil lately if not add a 1/2 quart of ATF when the engine is cold and bring it up to temp if it is not getting any oil it should start getting noisy. You can also pull the valve covers and see if the upper end is getting oil when the guage drops off but do a oil change first after the ATF treatment and smell your dipstick for fuel I have seen fuel pumps go bad and thin the oil out. I dont think it is the guage cluster or the other guages will drop also. I am guessing oil or oil pump start with the cheapest first. Oh yea does the pressure go up when you give it gas rev it up to about 3000 rpm for a few seconds to see if the pressure comes up it wont hurt the engine any more than it already is if it is bad berings.

 

[OilPatch197]

change oil weights might give higher pressure to compensate for worn engine.

or put in a bottle of STP oil treatment, see if that helps.

 

[OilPatch197]

I was also a mechanic on a demolition derby team. A lot of these cars run wide open (or nearly so) for maybe 15 minutes at at time, sometimes with little or no coolant.
We used to run some of these cars with 100%, or nearly 100% STP oil treatment in the crankcase. You got to remember that most of these engines were real loose and sloppy.

 

[xkotyx]

i changed the oil the other week when i got it. first thing i did to it. it doesnt smell like anything but oil.
and i did forget to mention, if i hold on the gas alittle, the pressure slowly rises back up. but then drops as i let off.

 

[OilPatch197]

personally it sounds fine to me, the gauge could be *not* that accurate. What was the recommended factory oil weight for that motor? 10w40?

Most engines only need around 10psi per 1000rpms. You could get a cheapo mechanical gauge temporarily to test pressure. Then you can up the oil to 15w40.

 

[xkotyx]

personally it sounds fine to me, the gauge could be *not* that accurate. What was the recommended factory oil weight for that motor? 10w40?

Most engines only need around 10psi per 1000rpms. You could get a cheapo mechanical gauge temporarily to test pressure. Then you can up the oil to 15w40.

yeah i think its 10w. ill get a cheap gauge, and after it runs alittle more, ill up it to 15w.

lets hope its just the gauge haha

thanks for your help!

 

[kimcrwbr1]

Did you touch the sending unit wire to ground the needle should peg on high if it dont the guage is probably bad but if all the guages go lower after a bit then the supply for the guages is bad you should be getting about 8 volts pulsing to the wire going to the sender if that voltage changes it is the power to the guages. A mechanical in line pressure guage is your best bet for monitoring oil pressure at least it is getting oil.

 

[xkotyx]

Did you touch the sending unit wire to ground the needle should peg on high if it dont the guage is probably bad but if all the guages go lower after a bit then the supply for the guages is bad you should be getting about 8 volts pulsing to the wire going to the sender if that voltage changes it is the power to the guages. A mechanical in line pressure guage is your best bet for monitoring oil pressure at least it is getting oil.

havent gotten around to it. i gotta charge up the battery first. just been busy and havent fooled with it. had a water leak at the new home, so just been busy working on getting all that fixed up.

ill get around to it when i get the next chance to mess with it. id like to see it running good eventually! haha

thanks for the help guys!