Oil light

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naa10104

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Joined
Jul 26, 2014
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Location
Reston, VA
My Car
1973 Convertible, matching #'s H Code, Auto
Hello,

      Have a 73 vert with 351 C 2V . Runs fine ... no issues.  Last night was out and noticed that at traffic light stopped in drive the oil light would flicker and come on solid or just flicker.  If I put the car in neutral which increased the rpm's the light would go out.  While driving the light would stay off.  I have a set of Bosch mechanical guages installed which show engine temp at 190 - 195 degrees.  Car has proper level of oil in it.  The OP guage shows app. 25-27 pounds at idle and and app. 50 pounds while driving.  On initial startup the pressure is at app. 75 pounds until engine warms up.  I believe the oil light is coming on do to a loose wire or maybe a bad oil sender, which is original to the car.  Any thoughts ?  Thanks

 
Hello,

      Have a 73 vert with 351 C 2V . Runs fine ... no issues.  Last night was out and noticed that at traffic light stopped in drive the oil light would flicker and come on solid or just flicker.  If I put the car in neutral which increased the rpm's the light would go out.  While driving the light would stay off.  I have a set of Bosch mechanical guages installed which show engine temp at 190 - 195 degrees.  Car has proper level of oil in it.  The OP guage shows app. 25-27 pounds at idle and and app. 50 pounds while driving.  On initial startup the pressure is at app. 75 pounds until engine warms up.  I believe the oil light is coming on do to a loose wire or maybe a bad oil sender, which is original to the car.  Any thoughts ?  Thanks
Click to expand...
As a point of reference, my '73 H Code Vert with the original never rebuilt engine (50Kmi) idles at 45-50 psi.

 
Last edited by a moderator:
25 psi is OK at idle, just not great. It's likely the oil pressure switch (sending unit). After 46 years the spring in the switch is probably tired. The idiot light comes on when the switch provides a ground, so if it's not the switch the wire to the switch is shorting out. Test it by pulling the wire off the switch and driving around. If the light comes on with it disconnected it is the wire shorting out.

You didn't say what oil you are using or how long it's been since the oil and filter were changed.

 
25 psi is OK at idle, just not great.  It's likely the oil pressure switch (sending unit). After 46 years the spring in the switch is probably tired. The idiot light comes on when the switch provides a ground, so if it's not the switch the wire to the switch is shorting out. Test it by pulling the wire off the switch and driving around. If the light comes on with it disconnected it is the wire shorting out.

You didn't say what oil you are using or how long it's been since the oil and filter were changed.
Click to expand...
Hello,  thanks for the info.  My engine has 63k miles on it and has been rebuilt once before I owned it.  I change the oil once a year as I only put app. 1K miles on it.  New filter and oil, good grade 10W -30.

 
Just fixed the exact same problem today. Oil light flickered on and off or stayed lit when idling. Went off in neutral or when I stepped on the gas. Oil level was fine. Just changed it using 20-50. Swapped the sensor and that fixed the problem.

Hope that works for you.

Mike

I'm just fixin' to get ready to start to get going.

 
Just fixed the exact same problem today. Oil light flickered on and off or stayed lit when idling. Went off in neutral or when I stepped on the gas. Oil level was fine. Just changed it using 20-50. Swapped the sensor and that fixed the problem.

Hope that works for you.

Mike

I'm just fixin' to get ready to start to get going.
Click to expand...
thanks for all the advice, a few additional questions.  My main concern is do I have a bad oil pump ? one of the manuals I have says my motor should be making 45 - 75 lbs of OP when hot.  Mine is 25-27 at idle hot .... is that a problem ?  Could a thicker oil correct this ?  One of the comments was to test the OP with a reliable guage, is this to verify what my Bosch mechanical guage is telling me or would the test be more accurate ?  I am assuming that I would connect this gauge to the port where the current OP sender switch is located. I will check into the sender switch which probably needs to be replaced.  Wondering if a good starting point might be to install a new sender and change the oil to a thicker grade and see what that does to the OP and the flickering OP light.  Again thanks for the advice !!!

 
I prefer to do one thing at a time. If you go to a different oil and change the oil pressure switch at the same time you won't know which one fixed the idiot light problem. I would start with the switch and see if that solved the light problem and then go to the new oil and see what that does to your idle pressure.

The Bosch mechanical gauge should be good, but as has been said many times on our forum, new does not mean good. I have an SW gauge that I know is good that I use for testing.

You didn't say how many miles are on your engine. The most likely causes of dropping oil pressure are worn main bearings, worn rod bearings, worn camshaft bearings, worn lifter bores, worn oil pump, and stuck oil pump pressure relief valve. Oil pumps typically supply more pressure than needed, and the excess pressure is relieved through the pressure relief valve.

 
I prefer to do one thing at a time. If you go to a different oil and change the oil pressure switch at the same time you won't know which one fixed the idiot light problem. I would start with the switch and see if that solved the light problem and then go to the new oil and see what that does to your idle pressure.

The Bosch mechanical gauge should be good, but as has been said many times on our forum, new does not mean good. I have an SW gauge that I know is good that I use for testing.

You didn't say how many miles are on your engine. The most likely causes of dropping oil pressure are worn main bearings, worn rod bearings, worn camshaft bearings, worn lifter bores, worn oil pump, and stuck oil pump pressure relief valve. Oil pumps typically supply more pressure than needed, and the excess pressure is relieved through the pressure relief valve.
Click to expand...
Hello,

I have owned the car for app. 5 years ... it has app. 63K on it.  My understanding is the engine was rebuilt in roughly 2013.  I can't tell you exactly what was done, but i do know some head work was completed and earlier in the 1980's or 90's a replacement block was installed. It runs well and seems strong.  I have never done a compression check on the engine ... I could do so if that is necessary.  To check the OP with a second guage does it get connected where the oil sender is located ?  Thanks

 
Yes, that is where I would check it. Where do you have the Bosch gauge connected, a tee at the sending unit?

That location is after the oil has passed through the engine, and gives a better idea of overall engine condition.

 
Yes, that is where I would check it. Where do you have the Bosch gauge connected, a tee at the sending unit?

That location is after the oil has passed through the engine, and gives a better idea of overall engine condition.
Click to expand...

Yes, Bosch guage is connected at a tee at the sending unit.  Thanks

 
I believe the 45-75 psi number you quoted is with the oil warm and the RPMs at about 2000. The Ford manual will confirm the exact RPM. As others have said, change the sender. Chuck

 
I believe the 45-75 psi number you quoted is with the oil warm and the RPMs at about 2000. The Ford manual will confirm the exact RPM. As others have said, change the sender. Chuck
Click to expand...
Thanks,

Little further for whats its worth.  Just went out and noticed a very small amount of oil on top of the motor where the tee is screwed in at the oil sender port. Not a puddle just damp.  It seems that oil is weeping either from the body of the sender or where it screws into the tee.  This is something fairly recent as I check this area occasionaly. I will replace the sender, curious could this cause the lower OP reading or OP light issue ?  Thanks again for the info. !

 
Most likely related to the light issue, the switch is (has) failing internally. It's doubtful if it's leaking enough to affect the gauge, you would be making big puddles if it were.

 
In my case the problem started right after I changed the oil and filter. It was the first time I changed the oil since I bought the car last fall. The PO said he had just changed it and it looked clean on the dipstick so I put it off. I used 10-30. Right after I changed it the light started coming on. I changed the oil to 20-50 hoping the thicker oil would help but no luck there. The oil level was fine, no puddles or noises, so I put a new sensor in. Been driving around for a couple of days and no light.

Sent from my SM-G950U1 using Tapatalk

 
I Installed the new oil pressure sending switch today and the red light on the dash is no longer coming on. Inexplicably the oil pressure has improved at idle. The oil pressure switch has nothing to do with the gauge reading so maybe the minor leak was enough to lower the pressure a little. Time will tell. Thanks for all your advice appreciated.

 

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