hello everyone, glad to post first question on the new board....

ok, here's my problem now, when I drive my f150, 4x4 302cid truck, I'll drive it so that is will come to operating pressure, then it will be fine, but a little after that, my oil pressure gauge says that my oil pressure drops to the "low" side!!!! But this only happens when I stop. However, if I put the tranny in park, then the pressure will rise again?? Whats happening?? When the oil pressure is low I don't hear any knocking sounds, or any rattling of my bearings, but i can't think of what the problem is..


thanks for your help in advance,

Oniram

 

Dear Oniram,
You do not state the area of the country you are in. Is it hot or cold? What type oil are you using? Sometimes 10w30 gets to thin in hot areas. Try changing oil. See if that helps.
I prefer Valvoline in my truck. If that does not help have a oil pressure guage hooked up and see your exact pressure. It would be a shame to loose your engine.

 

There are several factors that contribute to low oil presure, first a bad oil pump, not likely, due to good oil presure at higher speeds, worn main and/or rod bearings, type of oil, temp of engine, and / or a bad sending unit. What type of oil are you using, and what part of the country are you in? Let us know and we will post with suggestings.

Dave

 

Depending on how many miles you have...You could either have a faulty sending unit, or you could see the initial signs of excessive wear on the engine internals. Worn bearings/oil pump symptoms can cause your condition. The oil pressure rises when the engine is running at a higher RPM. If you don't have any urgent problems, I suggest planning on a replacement set of bearings, and a pump in the future when you have the money and the time to do it.

 

Not knowing specific psi numbers, sounds normal. Idle pressure usually drops when the engine warms up and increases with rpm. Best thing to do is get a cheap K-Mart mechanical oil pressure gauge and see what the real numbers are. Should have 10-15 psi at idle and 45 psi at 2000rpm. Doubt if you have a problem. Electrical pressure gauges in Ford trucks are little more than symbolic.

 

Mine did the same thing and it turned out that the oil strainer was getting stopped up. $20 and a couple hours and it all returned to normal.

 

My 87 F-150 is doing the same thing, can you tell me where the oil strainer is located?

 

You emailed me back with the question that the vacuum tubes are going, what are you talking about? Also the belt wont have any effect on the oil presure, unless it is letting the engine get too hot. The possibility that you have something in the oil pan and plugging the pickup tube screen is very slim, check your oil presure with a mechanical gauge, or change the sending unit first, if the problem still exists, plan on changing out your rod and main bearing, a job, but it can be done with the engine still in the truck. let us know

Dave

 

I would just like to thank everyone that has taken the time to, help me with this problem, and I think that I am going to start with the screen, and try to replace that, and I will get back to you guys on the results..


Thanks again,

Marino

 

Unless you have reason to suspect the pan is full of junk and the screen stopped up I would certainly change out the oil pressure sending unit and gauge or like previously posted put a mechanical gauge on it. The gauges on my '88 302 were flaky from day one. Ford replaced gauges two times but did not fix the problem. I replaced with a mechanical gauge and from then on I knew what my pressure was. 120K miles later it still ran like new and had good pressure. Good luck.
ray

 

Have you gotten any responses to your question? I am having the same problem with my 97 F-150.

 

If you do find with a mechanical gauge that you do indeed have low oil pressure, you may want to remove a valve cover and check for evidiance of worn/broken/hard valve stem seals laying around in top of oil valley. If after you confirm this you may want to see if screen has some pluging it up. Only problem now you will be faced with if it is plugged and then you must determine if your rod bearings are gone> I suggest spot checking them. GOD BLESS