Thread: 390 Oil Light

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I have a 64 Galaxie with a 390. When I drive the car for more than 10 minutes (enough to warm up completely) the oil light comes on. It doesn't just light up, though, it slowly flickers, very dimmly when I come to a stop sign (i.e. when I put a greater load on the engine. It's an automatic). Eventually it stays on bright. When the engine cools this starts all over. The engine runs good and strong with no temp issues even when the light comes on. the temp gauge shows right in the middle.

Initially, I thought the oil pump didn't like the thinned (hot) oil. But this engine has all factory parts and I changed the oil pump with a new-original replacement. I still get exactly the same issue with no variation. If it were the pump, it's not likely I would get the same symptoms on two different pumps. I'm going to try to change the oil sending unit today, but my question is this:

To my knowledge, only the pump and switch affect this oil light. Is there anything else that might cause the light to come on like this? In case it matters, I had the timing set on the car recently after I rebuilt the heads and it runs like a champ, but I never had this issue before.

Have you checked the oil pressure with a mechanical gauge??? Could be some bearing clearance issues causing the low oil pressure, might want to put a mechanical gauge on and see what the pressure actually is....

Put a guage on it. I've seen old Ford senders that put the light on at 20lbs. Yours could be worse.
If the pressure really is low, the bottom end needs rebuilding, or maybe the cam bearings are shot. Either way, its time to pull the engine.
Could the pump just be loose? Or maybe the drive shaft is rounded off and slipping? A long shot, but it happens.

The engine was completely rebuilt 3K miles ago. Everything had been running great until now. The car runs great, so I'm hoping there's nothing too serious wrong.

Could just be a bad sending unit. Might be best to check it with a gauge and know for sure, though.......

I think the internal resistance of the sending unit is breaking down as it heats up, it appears to be acting more like a temp sending unit.

That makes sense. I'll change the sending unit tonight and give it a test drive.

It may have taken me 3 weeks to change the sending unit, but I did it. The light stays out now. So, for anyone else who has a light that comes on after the engine warms up, it's most likely a sending unit.

It's always best to change the easy stuff first. Thanks for the input, guys.