I have a 2002 Ford Ranger that doesn't have a real oil pressure gauge
- it has one of those "fake" gauges that always shows either zero or half scale. The oil pressure has always behaved normally (i.e. it's not zero :-) until a couple weeks ago when we took it for about a two hour drive.
It was fine on the freeway but when the engine was idling in the hotel parking lot I noticed that the gauge was "twitching". Since the gauge can't actually show any real values, my guess is that it's just intermittently oscillating between zero and normal, but the gauge is too heavily damped for it make the full swing. No warning lights, if that matters.
I shut it off and it sat there in the lot for about an hour, and when I cautiously started it up about an hour later it was normal again. Steady pressure reading. In a couple of days of short trips driving around town it behaved perfectly normally.
Until, that is, we took a two hour drive to get back home, and by the end of that trip, it was doing the exact same thing again. But since then it still behaves normally for trips, even as long as 30-40 minutes, around town.
Even a 30 minute trip seems like it should be enough to get the engine and the oil plenty hot, especially with the A/C running and the hot weather. I just can't think of anything that fail after two hours that wouldn't do the same thing sooner, and it's really difficult to troubleshoot a problem that requires two hours of driving to reproduce!
Any guesses as to what might cause this?
Thanks, Bob Armstrong