After a 45 minute drive at higway speeds, the oil pressure light in my truck comes on at idle with tranny in Drive. Goes out when tranny placed in neutral. Could the oil pump or relief valve be at fault? Pressure sender? Motor runs great and doesn'trattle or knock, but it is a high mileage unit I'm sure. Any hints or advice appreciated. Davey

could be any of the three but my best guess would if it has high miles over 100 thousand miles and by what you describe .1 oil pump 2 relief vavle 3 sending unit. Maybe Dan or Charlie or Lou can help you better on this. Thanks Ron Parker









Bagels On Juice Im On Boost

Go ahead and service the oil pressure relief valve, see this thread and this one. And put a new sender on it while you're down there. What grade (viscosity) of engine oil are you using?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I just changed the oil in it and used a good filter and straight SAE 30 oil. No particular reason for this, I just had some. I use 15W40 in everything else, maybe that would help this old slant. What do you think?

Where do you live?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I live in South Carolina, and the summers here are brutal. If this old motor is loose enough that the OP light is on after a mild warmup in February, I'm concerned that it will really be bad in August. Surprisingly, the guy that had it before me actually had air conditioning on it. I haven't had a chance yet to ask if he noticed the huge red oil light shining in the summer when he had all that cold air blowing in his face. Davey

Mine does the exact thing you are describing, Davey. 76 Feather Duster, stock except a Super Six, with roughly 30,000 on the clock(130,000). My light generally only comes on when I haven't changed the oil in a while. I put a new oil pump and sending unit on it less than two years back. I'll try the relief valve servicing described in other threads and hope it works.

Maybe the engine is gunked up in some key places that might reduce pressure...? I'm not yet knowledgeable about these things...

Billy

Billy, do you ever go to "sweptline.org" ? This is another great website, and under the engine forum I asked this qestion there too. I got some great answers. You might want to take a look. I'm going to do a couple of things, I'm going to either Rotella 15w40 or 20w50, and I will add a quart of Lucas oil stabilizer. If this doesn't solve the prob, I'll look at a new oil pump. Davey

My valiant did that when I first got it. I put main and rod bearings in it and a new oil pump. I also put a mechanical guage on it. Now with the engine idling, it makes 30 psi of pressure. After all that, I happened to read in my owner's manual it actually says that it is okay if the light comes on at idle as long as it goes away when the rpms pick up! Has anyone else read that?

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69 valiant

Yep, that's in the manual, you didn't hallucinate it. Technically it's true, given the allowable minimum oil pressure at idle and the production (& resultant performance) tolerances in oil pressure senders. But, it's also possible to fix things so that this doesn't happen, and I do not regard the oil pressure light being on when the engine is running and has adequate oil pressure to be acceptable under any conditions. It spoils the ability of the light to warn when there's actually a problem!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.