Weird oil Pressure

[easyed]

I have a 1989 Ford F-250. When I am driving down the highway my oil pressure is normal. When I sit at idle in park or neutral my oil pressure is normal. Once the engine temp gets to normal operating range things change. When I step on the brake and come to a stop my oil pressure goes to zero. When this happens I can quickly shift to neutral or park and the pressure returns to normal. What's happening and how can I fix this.

[ September 13, 2004, 10:04 PM: Message edited by: easyed ]

 

[Geoff]

On an engine that age I'd say you have a plugged oil pickup and/or worn engine bearings. Either would drop oil pressure and cause the oil light to come on at idle when the pump is putting out the lowest volume. On Ford's (I think even the '89s) the oil guage is really just an idiot light with a needle. It moves out of "normal" at a certain pressure.

The screen can get plugged from varnish or a sloppy oil pan sealing job. How does it look down the oil filler cap? If you are mechanically inclined I would drop the oil pan and check it out.

I would run a good heavy duty oil like Chevron Delo 15w40 (blue jug at Walmart) and change the oil/filter often. They have a lot of detergents and could clean things up fairly quickly, and the viscosity should help maintain pressure.

 

[BIGJ552000]

I think if it really is at 0 psi. your engine would be dead by now. So my guess is replace the gauge.

 

[tpi]

You probably are the victim of a Ford oil pressure idiot gauge. The gauge registers normal at anything over about 5 PSI. Below that it will read zero. There is no in-between. First off I'd change the sensor, it may be out of spec. If that doesn't work, I'd increase the viscosity (if the engine isn't making unusual lifter or bearing noise).

I currently have a 99 F250 with a full complement of idiot gauges. The alternator completely failed in July and the voltmeter maintained its "idiot normal reading."

Rant: Automakers stop installing these useless gauges.

 

[Gary Allan]

easyed

Can we assume that you have no accompanying lifter tapping or "rumble" from the engine when this occurs?

If no, then the aforementioned idiot gauge is the probable cause. At zero oil pressure ..you will hear "stuff".

If yes, you may want to pull the pan and consider an oil pump upgrade/swap (I'm fond of high volume pumps myself =-= they're not for everybody). This would probably compensate for a few loose tolerances ($50-60 and a few hours work for a few more years type thing).