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Oil light suddenly started staying on too long on start up


Jerry
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Seasons greeting MJ guys 👋

Old Timer here 🙂🛻

 

Quick question for the experienced 4.0L mechanics out there if ya don't mind.

 

My daily driver MJ 4.0L that's been running faultlessly for me over the last 13 years through thick and thin, now has an issue I'm worried about 😕

 

The oil light (idiot light, no gauge) has suddenly started staying on for a few seconds after it fires up. It's never done this before. My first guess was the oil filter non return valve got stuck, so I swung by jiffy lube and got it changed but that made no difference.

Once running the light stays out even at idle and all sounds well in the motor bay. No leaks. I can stop for a half hour and restart and the light goes out immediately as it should. But over night the problem comes back.

To me this all sounds like the filter draining back. But how likely is it for a new filter to also have a failed non return valve?

 

Is there another explanation you can think of? Is there a built in non return somewhere that could have failed? Sensor maybe? 🤔

 

Any help or pointers appreciated. I don't want my DD wearing out before it's time because it's oil starved for a few seconds each morning!

 

Thanks in advance, pic for attention 😉

 

20170824_151406~2.jpg

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47 minutes ago, Pete M said:

the switch that activates the light might be due for replacement.  maybe time for a cluster upgrade to one with a fancy gauge?  :D 

You mean the pressure sensor by the filter Pete?

and

Nah, I like my simple idiot lights 😁

 

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6 minutes ago, Pete M said:

yes, that's the one. :L:  without a gauge, there's no telling what your pressure really is. 

OK, thanks I'll check that out. Maybe ask my local garage to pressure check the system. Guess it could simply be a dirty connection to the sensor.

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Thanks for the pointers guys. I'll get a new filter from Napa. I'm told they are good quality. I'll clean the connections anyways but my observations point to drain back. Once the motor has been started and ran a couple of minutes, when I shut her off and restart the light goes out immediately as I'd expect, indeed as it always had before 👍 

Does anyone know if there's a drain back valve in the pump too? Or only the filter?

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  • 3 weeks later...

Hmmm!? So I put on a new filter and everything was normal again ... for a short while. So it seems the filter is not the cause. I don't think the sensor is the issue because it appears to be showing what I'm physically seeing which is ... on removing the old filter after leaving overnight, it was completely empty of oil ... like actually EMPTY, completely dry. On start up in the morning the light stays on for the amount of time I'd think is about right for the filter to fill up then goes out, about two or three seconds. Then on starting again after a couple of minutes it goes out immediately as it should.

 

My local parts guy suggested the PCV valve could be clogged causing pressure in the crank case side of things and therefore pushing the oil back through the system.

 

Does that sound possible guys?

If so, where does that live under the hood? So I can take a look at the weekend.

 

Cheers all, happy Friday 😀

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Bit of a head scratcher eh!

It never used to do this and it seems to be intermittent. 🤔

It'll probably just stop doing it at some point lol 😁

There's minimal oil leaks, a little around the valve cover but otherwise ...

Only 150k miles on it.

wtf :dunno:

I'll just keep on Jeeping on and ignore it then. Thanks for the input chaps. Let you know if it explodes 👍

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9 hours ago, Jerry said:

My local parts guy suggested the PCV valve could be clogged causing pressure in the crank case side of things and therefore pushing the oil back through the system.

 

Does that sound possible guys?

If so, where does that live under the hood? So I can take a look at the weekend.

 

 

The 4.0L doesn't have a PCV valve. There's a [very] small tube coming off of the top rear of the valve cover that fulfills the crankcase ventilation function, but there is no physical valve. And, yes, that scrawny little tube can get clogged over the years. Whether that could pressurize the crankcase enough to force out of the oil filter overnight is something I don't care to guess at.

 

How's your air filter? If the element is soaked with oil, your CCV system is clogged. If your air filter element is not soaked with oil, that's not the problem.

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I doubt that crankcase pressure has anything to do with it. The pressure in the crankcase pushing down on the surface of the oil in the sump is going to generate a ton more force than what you'd see at the other end of the oil passages, which if anything would just push the oil back up the pickup into the filter. And if there was enough pressure building in the crankcase to move oil around the engine, it would probably have started leaking oil out of more than just the valve cover gasket by now, just like Pete's engine. But it's still worth checking to see if your CCV system is clogged, you do kinda want that working and it's had issues on every Jeep I've owned to date.

 

My guess would be a leak in the oil passageway from pump to filter that's somehow allowing air back into the system, but I would also expect it to be leaking oil if that were the case, and if that's not an issue... ¯\_(ツ)_/¯. Lots of the equipment in our fleet does that too, take a few seconds for oil pressure to build, and nothing seems to suffer too much from it.

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