What does "oil - low pressure" light mean when it just barely starts coming on?

[jpilk99]

I'm out there brush-hogging and noticing, after 10-15 mins that the oil - low pressure light on my odometer is flickering/glowing coming on when really under load and then goes off when rpms climb back up. I checked oil level before use and it was good. Any thoughts? Normal??

Thank you,

Jay

 

[/pine]

I'd check the wire on the sensor...

 

[Eagle1]

on my old truck it means I'm a quart and half low if it flickers up hill.

 

[Raul-02]

after 10-15 mins that the oil - low pressure light on my odometer is flickering/glowing coming on when really under load and then goes off when rpms climb back up

Ummm check your oil.
Just do that and, don't overthink it.

 

[JimRB]

One of my cars like 20w50 oil. Oil light would come on with thinner oils. Note that it is a pressure switch, not an oil level switch.

I had an oil light come on in my Toyota. Turned off engine and got a tow back home. New oil pressure sending unit fixed that problem.

 

[Eagle1]

Yeah but if my truck is low on oil the pressure varies. YMMV

 

[Hay Dude]

I'm out there brush-hogging and noticing, after 10-15 mins that the oil - low pressure light on my odometer is flickering/glowing coming on when really under load and then goes off when rpms climb back up. I checked oil level before use and it was good. Any thoughts? Normal??

Thank you,

Jay

Are you on hills? Sometimes that can make warning lights come on.
I could see where REALLY under load could make a oil pressure light flicker- like close to stalling.

 

[JC-jetro]

several things could cause it.
1- Your oil sender unit is defective or close being defective. Sender is a normally closed switch by action of an internal spring. Upon start up, it maintains a closed circuit hence oil light pressure illuminating. As soon as pump start pumping oil, then the oil pressure will opens the switch and then oil pressure light will go out indicating pressure. Now this is for only "idiot light". The sender could also have a variable resistor, calibrated to digital or analog(needle) that actually shows pressure. This one is more preferable but mainly used on some automobiles more so than tractors.

2- If your oil level is low and you are in an incline (up or down) then you oil pick up tube and screen might suck some air while pumping, causing the pump to cavitate a bit, not making pressure and illuminating the low pressure light. A partially clogged screen can cause that and to clean that engine pan needs to be removed.

3- There is a very low possibility that your gear driven oil pump is damaged or has some restriction. This is very seldom a root cause but there is a possibility.

4- Check for loose wiring at the sending unit and also check all the fuses. Also check the connection at the back of tachometer.


By the way, I had to change my oil sending unit once 15 years ago. It was stuck closed.

 

[Doughknob]

How old is your oil?

 

[DK35vince]

If it were my machine, I would mount an oil pressure gauge so I could see what the pressure is.

 

[Sawyer Rob]

Keep in mind, it only takes about 2 pounds of pressure to make the light go out, so IF the wiring and sending unit is OK, I'd be looking for the problem SOON and not running it much until I found it!

SR

 

[sd455dan]

Keep in mind, it only takes about 2 pounds of pressure to make the light go out, so IF the wiring and sending unit is OK, I'd be looking for the problem SOON and not running it much until I found it!

SR

FIL just replaced his older 2 stroke 60HP outboard on his pontoon boat with a new 85 HP Suzuki 4 stroke ~$10000 with controls and install.
He just got the first 8 hours on the engine and oil light started flashing. Got the cover off and engine was at the correct oil level, limped it into the dock we took it to the dealer, sure enough defective sender.
Engine was idling with 60 psi warm. Of course no senders in stock so boat sits until the sender comes in. My TA Pontiac 455 still has a replacement mechanical gauge after 40 years because I got 2 defective senders in a row, just installed a mechanical may order another electric sender and try again. Those electric senders do go bad sometimes.

 

[PILOON]

I'm out there brush-hogging and noticing, after 10-15 mins that the oil - low pressure light on my odometer is flickering/glowing coming on when really under load and then goes off when rpms climb back up. I checked oil level before use and it was good. Any thoughts? Normal??

Thank you,

Jay

Under load the RPM's would be a bit lower.
Then most oils get thinner as thy get hotter.
Suggest you change for a heavier weight oil and give that a try,

 

[pmsmechanic]

We were taught in school that 10 psi oil pressure / 1000 rpm was adequate. So I would attach a mechanical gauge to the oil pressure sending outlet in the block and check your oil pressure. Chances are that there is something wrong with the oil pressure sending unit but if you check it with a mechanical gauge then you will know for sure.

 

[timbatrader]

the sender could be faulty or the big end bearings are getting sloppy and the pump can't pump enough volume of oil to the big ends , the pump could be worn if its an old tractor all three might things could be happening in such a way that each item on its own is acceptable but the three together are a problem

 

[Snezzy]

One of my cars like 20w50 oil. Oil light would come on with thinner oils. Note that it is a pressure switch, not an oil level switch.

I had an oil light come on in my Toyota. Turned off engine and got a tow back home. New oil pressure sending unit fixed that problem.

Back around 1975 a friend had a car with a device to SHUT DOWN THE ENGINE on low oil pressure. It did just that. Chugging along in the passing lane at high speed and the damned sensor fails, you'll lose more than the engine! Fortune smiled that day and no one was injured.

 

[motormike]

My JD use to do that. Checked everything and couldn't find it. Ran an engine flush through, changed oil and filter. Its been 2 years now with no flickering light.

 

[JWR]

I doubt anything is wrong. Add half a qt of oil and see if the disease goes away. Are you sure the light means ENGINE OIL only ? You may have transmission / chassis / hydraulic oil indication instead. Mine did that at times and I found it was indirectly a reminder to go change the hydraulic fluid filter.

 

[rScotty]

That's a fairly common problem for the hydraulic system. Maybe the engine oil is the same thing. For hydraulics there isn't an idiot light but low pressure still means that the oil filter is needs changing and that is starving the pump for oil.
(Edited with later info from JC-jetro)

 

[JC-jetro]

That's a fairly common problem. It sounds like the oil filter is needs changing and that is starving the pump for oil. If your Ford is a model from the 1970s to late 80s, it probably also has a spin-on filter and also a cleanable hydraulic filter. The problems is usually in the cleanable filter which needs to be pulled out and cleaned. Check your owner's manual, it has the instructions on both.

On 1700 cleanable screen is for hydraulic only and it does not have any pressure gauge or idiot light. Spin on filter is for the engine oil and obviously crankcase oil and hydraulic oil are totally separate. The issue with OP and his problem is with crankcase oil. All the posters accurately explained to OP root causes, he just needs to chime in.