Oil light flickering at low idle

[EcoB00ST]

I've done a google search and this sounds like a common issue with lots of people asking about it. However the responses I've read are inconclusive. I wanted to run it by the BITOG community for hopefully some better expertise.

The oil light flickers when the engine is hot and the oil thins a bit. It only does it at low rpm idle which can only occur when the engine is in drive and I'm at a complete stop. This is where RPMs settle to about 500. That's where it starts to flicker. Only if the engine has been run for a bit. If the engine is not hot enough it won't do it. Also, if I flick the shifter into neutral or park, it will go away because that makes the RPMS go up by 200-300. Just enough to increase oil pressure enough to turn off the light. Based on the fact that it only does it when the engine is warm leads me to believe it is an actual pressure issue and not a bad sending unit because it can differentiate and will only do it with hot thinner oil and not when the oil is thick prior to proper warm up. Just did an oil change to maxlife 10w 30. Prior to the oil change it would do it faster. The fresh oil slowed down how long it took for it to happen, but after it heats up enough it still does it. What could it be? Engine just getting tired? Oil pump? Clogged pick up screen? It did first happen on a run of Auto-rx about 1 oil change ago and has been happening since. I don't believe I could have had that much sludge in there. Obviously I'm a bitogger and use good oils, with more than safe intervals, and my motor is not a known sludger. But i do know after running the auto rx it could have still plugged up the screen a bit.

If anyone has experience with this problem, please let me know what it ended up being.

Thanks!!!

 

[OVERKILL]

What engine are we discussing? Any way of fitting an actual pressure gauge to it to glean real oil pressure?

 

[EcoB00ST]

PS. It's a 2000 Chrysler 300m 3.5 v6 w/ 206,000 miles. Runs well other than the oil light.

 

[EcoB00ST]

I don't have a gauge but I've been looking into them, they're not that expensive. That was going to be my first DIY attempt. Was just hoping someone has experienced the same thing here and could save me some trial n error time.

 

[qdeezie]

Do you know the history of your engine since new?

Might want to try swapping out your oil pressure switch to see if there's any difference. It's definitely worth trying.

If you swap out your oil pressure switch and it still does the same thing........you more than likely have some bearing clearance issues.

That would be my take on it.

 

[OVERKILL]

It isn't really trial and error. Verify oil pressure. That will tell you where you stand.

 

[d00df00d]

Originally Posted By: qdeezie
Do you know the history of your engine since new?

Might want to try swapping out your oil pressure switch to see if there's any difference. It's definitely worth trying.

If you swap out your oil pressure switch and it still does the same thing........you more than likely have some bearing clearance issues.

That would be my take on it.

Mine as well.

 

[AKhan87]

Originally Posted By: OVERKILL
It isn't really trial and error. Verify oil pressure. That will tell you where you stand.

+1, If the oil pressure switch is good then bearing issue.

 

[EcoB00ST]

Yea. I've been thinking maybe change the pressure switch first (cheapest option). If it still happens then prob going to get a gauge to see where I'm really at. If it turns out that pressure is actually a bit low at low idle, what should I do? Would a slightly thicker oil help? I'm not trying to get another 100k out of the motor. Maybe just another 20k will get me the time I need. Its a 15 year old car and has served me well, looking for the most economical solution here.

 

[OVERKILL]

A thicker oil would be a bandaide but it will depend on what the actual pressure reading is. You just need a cheap oil pressure gauge, plumb it in place of the sender and verify cold and hot pressure at idle. Report back.

 

[Ursatdx]

It's probably the sending unit.
There was no mention of unusual engine noise.
Just my .02
And I would have run the ball.

 

[Trav]

You must get accurate oil pressure readings as others have said.
If the pressure is lower than spec you may well be dealing with a partially clogged oil pick up screen, oil pump issue in the relief circuit (eg clogged with debris or sludge), clogged oil passages or bad bearings.

If the engine is quiet at startup and running i doubt bad bearings, many Subaru EJ and old MB diesel engines had flickering oil lights (or gauges bouncing on the bottom peg) at hot idle and run for decades that way.
Not saying its okay or you should run it like this just the flickering doesn't necessarily mean the bearings are automatically toast.

If the pressure is lower than spec you can attempt to clean the pickup half arsed to at least clear most of the clog. More on that if you need to do it.

 

[mrsilv04]

Originally Posted By: Ursatdx
And I would have run the ball.


... I love it...

 

[bubbatime]

I had an old engine do this. Just bumped up to a 40 weight from a 30 weight. It was on its last leg and I sure wasn't going to do the proper repair of opening up the engine and checking bearing clearances.

 

[zrxkawboy]

I had this happen when I had my '96 Intrepid 3.5. As soon as it started to do this, I swapped the sending unit, and it never happened again.

 

[Trav]

It could be a clogged sending unit and hopefully thats all it is but if it gets changed and stops flickering it might only have enough pressure to keep the light out.
5-7 psi will keep the light out but its not enough to run the engine on.
I rather know what the actual pressure is, making decisions is easier when you know what your dealing with.

When the engine is at risk, half stepping is not the way to operate IMHO.

 

[gold01ca]

Just went through this only a couple of days ago on my old Toyota.
Oil light issues exactly as you described, flickering/steady on @ hot idle.
Turned out to be..............a bad oil pressure sending unit.
Just my very recent experience.

 

[Donald]

Originally Posted By: 300m2000
I've done a google search and this sounds like a common issue with lots of people asking about it. However the responses I've read are inconclusive. I wanted to run it by the BITOG community for hopefully some better expertise.

The oil light flickers when the engine is hot and the oil thins a bit. It only does it at low rpm idle which can only occur when the engine is in drive and I'm at a complete stop. This is where RPMs settle to about 500. That's where it starts to flicker. Only if the engine has been run for a bit. If the engine is not hot enough it won't do it. Also, if I flick the shifter into neutral or park, it will go away because that makes the RPMS go up by 200-300. Just enough to increase oil pressure enough to turn off the light. Based on the fact that it only does it when the engine is warm leads me to believe it is an actual pressure issue and not a bad sending unit because it can differentiate and will only do it with hot thinner oil and not when the oil is thick prior to proper warm up. Just did an oil change to maxlife 10w 30. Prior to the oil change it would do it faster. The fresh oil slowed down how long it took for it to happen, but after it heats up enough it still does it. What could it be? Engine just getting tired? Oil pump? Clogged pick up screen? It did first happen on a run of Auto-rx about 1 oil change ago and has been happening since. I don't believe I could have had that much sludge in there. Obviously I'm a bitogger and use good oils, with more than safe intervals, and my motor is not a known sludger. But i do know after running the auto rx it could have still plugged up the screen a bit.

If anyone has experience with this problem, please let me know what it ended up being.

Thanks!!!


A mechanical gauge is the only sure way to tell. Many oil pressure idiot lights come on at around 5 PSI. I had a 1994 Camry that did weird things with the oil pressure. Verified with mechanical gauge. Changed only the Amsoil EA filter (not oil) and the problems went away immediately.

Sender is a possibility (and cheap) if its a plain sender not a fancy one.