302 oil pressure question

1986 302 w/ 160k miles. Loses oil pressure at idle after driving approx 10 miles. Rev engine to about 1500 rpm and hold it there, pressure builds back up. Oil & filter change w/ 10W30 gives no improvement, oil & filter change w/ 20W50 cures problem for 100 miles, then the pressure starts dropping again. In your opinion, oil pump problem or bad bearings? BTW, when pressure drops, I do not hear any lifter clatter.

Is the engine all grungy inside? maybe it needs to git flushed.
Also it'sa cheaper to stick on a new oil pump than a new engine.

Also it'sa cheaper to stick on a new oil pump than a new engine.

Good point, try a new oil pump first.

Are you going off the stock gauge still? When pressure drops by how much are you talking? I would really suggest getting a more accurate gauge to monitor the exact oil pressure.

You have a 160k miles motor, it's going to start showing signs of wear. Low oil pressure can be associate with bad or warn bearings. As long as you don't get lower then 15psi, or spikes to 0, I wouldn't worry about it too much. Since you said pressure builds back up as rpms increase, things still sound ok.

Remember this; As oil heats up it thins out, and as oil thins the oil pressure will drop. Now a motor oil like 20W50 is a lot thicker, and will create more oil pressure cause of its consistency. But like any oil it will thin as the oil heats up. Since you motor has 160k on it, and you have oil pressure problems, I would start to run a heavier weight oil to withstand the clearances the motor now has cause of wear.

One other thing. Oil pumps are no fun to change, and I don't really see that as your problem. From what you described, everything sounds right for a motor with high miles on it.

On the stock Ford truck style gauge, after 10 miles driving, when I stop at a light, the gauge will drop all the way to the left indicating no oil pressure. This is with 20W50. One thing I don't understand, if the oil pressure is that low, shouldn't I hear lifter clatter?

So it only drops that bad at an idle? When cruising it's good? I would get an aftermarket gauge, something cheap, but good enough just to get a more accurate reading. The stock gauge will drop off after pressure reaches a certain level. So in reality you might have, say 5psi, but the gauge will read 0, that's why you don't hear lifter clatter.

How does the rest of the truck run?

Everything else is just fine. Allways starts up, runs like a champ. The only real problem I've ever had with it was the time the fuel pressure regulator went out, what a mess, gas everywhere. Even the air fiter box was soaked. I just wish Fords didn't rust so bad.

Fritz the Cat, i have the same oil pressure problem in my 92 302 5.0 , i am getting a new oil pump done today, did you resolve your problem, and how, maybe i can let you know if this worked for me, please send me a email @ bradn38@comcast.net thanks

Change your sending unit first(lower right side of the block,above the oil filter-looks like a bell with a wire on top) or better yet,get a REAL,mechanical o.p. gauge.Ford OP senders are crap.So are their gauges.Especially tachs on 5.0 Mustangs.Mine was out almost 800 rpm from what THREE aftermarket tachs read.

Hi:

I drive all over the NW for work and this truck is great. It is just shy of 300,000 miles and runs like a champ. The oil pressure always reads right in the middle of normal, but last week it dropped below the "N" in normal but no where near low or danger.

I keep this rig in pretty good shape and am getting concerned. I know it has 300K, but my last 302 made it to 475K, so I have a long ways to go. I gather from the messages here that the best way to go is:

1] replace sending unit
2] check pressure with a real gauge.
3] clean pan and intake tube.
4] change oil pump
5] drive it til she drops
6] new engine

BTW there is no lifter or engine noise at all and it is not
that serious now, but why wait for something serious?

Any comments, and has anyone had luck in regaining pressure
from changing the oil pump?

Thanks,

Joe

i had the same problem with my 302 in an 88' f150 i changed the oil sending unit that screws into the driver side of the block and fixed the problem

I have a 89 bronco with 302 with the same problems. It's ok until the engine gets warm , but then it drop.There is no bad noise to hear fro the engine.
I have changed the oil pressure unit.But the problem is still there.
The engine has only 78 000 miles on it.

Try revving the engine to about 2000 rpms. If you feel a vibration the mains are weak. I have discovered this situation many times in the past.

I have a 89 bronco with 302 with the same problems. It's ok until the engine gets warm , but then it drop.There is no bad noise to hear fro the engine.
I have changed the oil pressure unit.But the problem is still there.
The engine has only 78 000 miles on it.


I have the same problem 89 Ford Bronco with 302. The oil pressure drops when I come to stop after the truck warms up. The oil pressure drops all the way down and the engine light comes on. What do I do?? I love my truck and I need help.

I have the same problem 89 Ford Bronco with 302. The oil pressure drops when I come to stop after the truck warms up. The oil pressure drops all the way down and the engine light comes on. What do I do?? I love my truck and I need help.

Hi

The problem was crank and bearings.:mad:

Regards Per Arne Sund

Hi

The problem was crank and bearings.:mad:

Regards Per Arne Sund
The mechanic says bearings also:( how freakin sad

I own a 1995 ford e-350 club wagon van w/140k miles on it...the van is in great condition, until this....I was driving about 65 MPH and slowed down to about 50-55 MPH when comming apon a stoplight...when all of a sudden a fire truck come out into the inersection with the lights on...i was about 20 yards from it when the light changed to red.....in an attempt to slow down quickly, i droped the gearshift into low 1 when i did this the van did what was expected and slowed very quickly, whitch reved the engine very high for the tranning to catch up. when the van came to a stop the engine died...i started it back up and i noticed the oil presure gauge was on the very low side and was "wiggling very fast back and fourth" so i reved the engine up and the pressure went back to normal til the RPMs went back down, then did it again. (and continues to be that way today) well i continued to drive the van to the nearest gas station and checked the oil and noticed it was 2+ quarts low added the oil to bring it back to full and checked for any oil leaks...found NO LEAKS at all. so i drove the van as normal for the next 2 days, and now there is a "clicking sound comming from the engine....but only after the van warms up (10-15mins)
and the sound is not all the time after hearing it for 20-30mins it sometimes gos away then comes back 30-+mins later. so it seems that there is a progressing problem....is there anyone out there that can help me get to the bottom of the problem....this is my only car at this time and most of the work i do is 60-70 miles away....so i'm traveling 4 days a week...PLEASE HELP... Thankyou -Brian

I have an '89 F-250, 5.8L, with the original oil pressure gauge, and an aftermarket PSI gauge installed, and even after adding nine quarts of oil, it still drops to zero PSI whenever I slow to a stop, or I'm moving really slow. Do you think it could be the oil pump causing the problem? Cause when I check the oil manually, it shows plenty of oil on the dipstick. Don't know what else it could be.

I have an '89 F-250, 5.8L, with the original oil pressure gauge, and an aftermarket PSI gauge installed, and even after adding nine quarts of oil, it still drops to zero PSI whenever I slow to a stop, or I'm moving really slow. Do you think it could be the oil pump causing the problem? Cause when I check the oil manually, it shows plenty of oil on the dipstick. Don't know what else it could be.

Most likely your bearings are getting worn. You might try running 15w40 oil and in the summer even adding a quart of Lucas oil stabilizer.

Do you know how many miles are on the truck? If you don't let the engine run for any length of time while on zero oil pressure it may well run you a very long time that way. Don't put too much oil in the engine, not much over the full mark on the dipstick.

PS I have a 1990 F-150 with a 302 that basically has the same oil pressure problem as your truck. I am doing as I advised you and it is serving me well.

Found out, the oil pressure only drops when the engine is warm. While it's cold, and it's cold outside, the oil pressure stays at about 40psi whether I'm running at speed, or coming to a stop. But as soon as the engine warms up, the oil pressure starts dropping and reducing to 0psi.

Found out, the oil pressure only drops when the engine is warm. While it's cold, and it's cold outside, the oil pressure stays at about 40psi whether I'm running at speed, or coming to a stop. But as soon as the engine warms up, the oil pressure starts dropping and reducing to 0psi.

That's pretty much how an engine with worn bearings acts. It could be your oil pump, but quite a job to replace with the engine in the truck. My guess would still be worn bearings.

How many miles on the truck?