I have a 1988 351 5.8 3 spd auto bronco. I'm losing oil pressure when the engine heats up and the rpm's drop below 1000. I had a mechanic tell me to replace the oil with 20w-50. Any suggestions?

 

Last time that happened to me I had the 351W motor rebuilt. If I was you I would listen real hard for motor noise. My main bearings were shot and I could hear/feel a rumble when I was on the freeway doing high RPM's.

 

it may mean that your main bearings might be going out. look to see if your crank pulley is at all slightly wobbling while the engine is running. mine did the same. started to lose oil pressure when about 10 min or so of running and notice a slight wobble on the crank pulley.

 

Did you do the rebuild or have a shop pay for it? What did it cost?

 

i just dropped a rebuild engine last weekend...$850 longblock (modern engines), and i believe its about $500+ for all the little things (IAC, cleaners, oil, power steering fliud. tranny fliud, spark plugs, ford 9mm wiring set, cap/rotor, starter, set of line tools, torx 30mm, engine mounts, exhaust bolts, etc etc...still fine tuning her) and the price still goes up and up....

 

You cannot trust the factory gauge. Do you hear any unusual engine noises when the pressure appears to drop? If not, it is probably ok. Try replacing your sending unit, it's easy to do.

 

Where's it at and how do I do it?

 

The sending unit is in the side of the block near the filter. Should be a single wire connector to it. It threads into the block. Its a matter of disconnecting the wiring and unscrewing it from the block. Install is reverse procedure. If you are concerned about loss of pressure, it might be a good time to install a mechanical gauge at this time to chekc the actual pressure as opposed to the "reading" that the factory gauge gives you. Which, by the way, is a misnomer since the factory gauge & sending unit responds to I think as little as 5 PSI which is hardly enough to protect your engine.

 

Thanks! I'll try that this weekend if I find time when I'm not in the woods.

 

OK, I purchased a mechanical oil gauge today. What do I need to look out for when installing it? Where can I find step by step instructions?

 

You could try converting your stock switch to a gauge. I did this on my 90 5.8L with great success. This is from a previous post of mine:
"The stock oil pressure gauge is actually a "switch", shorting to ground for any pressure over 6 psi. There is a resistor on the back of the instrument panel which allows the needle to show about 60% of fully reading when the switch (sending unit) is grounded.

If your needle only fluctuates at idle, it is possible that your oil pressure is running right around 6 psi, thereby the switch is turning off and on, causing the needle to fluctuate.

One remedy for this is to convert your oil pressure switch to a gauge. I did this on my 90 5.8L Bronco with great success. Take a look at this link. All you need is the variable pressure sending unit, an extension to mount it on, and a diode to "short out" the resistor on the back of the instrument panel.

http://www.sfuller.net/projects/cobra/oilgauge

Good Luck!"