Today my Dad and I bought a 1990 Bronco, 302ci 4X4. When we test drove it everything seemed fine all across the board. We had drove about 20 miles when we decided to engage the 4-wheel drive, when I got out to turn the hubs my Dad yelled for me to come take a look at the OIL gauge it was bottomed out! We killed the engine and sat there for a few min's. We then started it back up and the pressure was right back where it belonged? We drove off and all seemed fine.. we stopped at the next stop sign and my Dad put the clutch in and the pressure dropped again and the engine lights came on!!! We just drove it back to the guy selling it and shut it off, all along watching the pressure rise and fall at stops. The temp never rose and we felt/heard no noises from the drive train.... We talked to the guy and told him what happened, he said that the front seal was bad and that was the cause.... I dont think so! Anyway, we had already seen the bad seal and noted it. We went ahead and bought the truck. When we got it home we fussed around with it and checked it out further. We found: While at idle after initial start up the oil pressure is dead on, as it heats up it is still dead on. When we drove it up the block it repeated the same symptoms. We found a few recipts in the glove that were from the local Ford place and an independant garage that pretty much stated the same as we had encountered but from last year!!! THis guy sunk $1400 into the rear end having a 9" Auburn Posi installed 3 months ago. He is selling due to a divorce, he said he was going to build it into a "play" truck.. Does anyone have any thoughts on what could be going on?? The truck is in AWSOME cosmetic shape with NO dents and only minor hood chipping.. It has 130,000 miles on it now.

Sorry this was so long...

Thanks

Spitdriver

 

You don't say, but I assume there are no other symptoms other than low gauge oil pressure. I doubt oil pressure is actually going to zero, as you would have lifters clacking and main bearing knock. Probably a failing oil pressure sender or wiring defect to the gauge.

Don't lose focus on everything else while watching the oil pressure. Two professional pilots drove their L1011 into a Miami swamp, while focusing on a "bad panel light", which was actually the only defect.

Good Luck

 

try changing the oil. go with a 10w-40. when i picked mine up a few weeks ago it did the same exact thing. it stopped as soon as i change the oil. 1991 302 bronco

justin

 

Hook up a mechanical guage to it and see what the real pressure values are. You can pick up a mechanical dash guage for about $20 at any auto parts store, and you can just hook it up under the hood and watch while you idle/rev to see what's going on. Don't trust the dash guage.

 

ford oil gauges are a fake they are just an on off switch . definatly install a mechanical geuge and see what the true oil pressure is. the oil pressure sending unit is really just a pressure activated on off switch, your gage has a resistor across the back of it to keep the fake gage from going all the way up. you can use a sending unit from an older 302 thart is a variable resistor and cut out the resistor from the back of the gage and it should operate as a real gage.

 

Wouldn't it be a better idea to jumper across the resistor with a wire than to cut out the resistor? It would seem that if you cut out the resistor, you would break the circuit, and would get even less information out of the guage than before...

 

now that you say that big ric i think that is what was discussed a while back my mistake sorry

 

Here's a good thread on the subject:

https://www.ford-trucks.com/forums/s...il+%2Bpressure