302 oil pressure

[Jeff213]

I have been having the oil pressure indicator on the dash go on and off at hot idle when in gear. The check gage light cflickers on and off as the needle on the "oil pressure indicator (switch) bobs up and down, however this really happens only at hot idle after the truck has been under load. I don't know if its an electronic problem or what?

The idle oil pressure in gear is about 40 psi on cold start at higher rpm in closed loop mode and 18 psi when engine is warmed up idling around 700 rpm according to my mechanical oil pressure gauge. This should really not be enough to be kicking the dummy indicator on the dash from what I have read. should I be worried?

I here a very quiet tapping sound, barely audible sometimes unless I am using the stethoscope, or stick my head in the wheel well. I put the stethoscope on the heads and it really isn't any louder. It really doesn't sound like a lifter tick but It might be the start of one? I have a new melling high volume with less than 10k miles on it.

Am I worrying too much about an electronic problem? It seems to run alright still, and still sounds pretty good.

Also forgot to mention, new oil pressure switch installed 10kish miles ago too, did not fix problem.

 

[Blown]

This forum is for modified explorers and making modifications. Maintenance fixes, everyday question are here: Stock 1995 - 2001 Explorers

The gauge in mine did that, bounced the needle once warmed-up at low idle. Not a problem, just a sender issue, you got oil pressure. If you raise the idle it stops bouncing right? A new sending unit/sensor should fix that.

 

[CDW6212R]

I'd also aim at the sensor, hopefully you just got another bad one.

Be sure to use best oil, synthetic always, and check it to make sure it's always full.

My last two 98's use a ton of oil, I've missed one being too low, once. The engine was knocking some and I immediately looked at the dash, saw the engine light and shut it off. It ended up being about two quarts low, I typically have to add a little oil once a week(I'd forgotten to).

 

[410Fortune]

Make sure you get the correct oil pressure sensor for your year and engine

Mechanical gauge tells the tale the stick oil pressure gauge is more like just a dummy light. As these trucks get older I’ve had more and more issues with the stock oil pressure gauges and the aftermarket senders actually working with the factory gauge
Motorcraft would be the best part to use if it is available
18psi is a little low, you could be having some carbon issues inside the engine. I would start using some treatments
I have seen the inside of enough 5.0
To know low oil pressure at idle is usually just excessive carbon inside the engine… it can be cleaned out.
You should be running full synthetic or at least semi synthetic oil and change it 3-5 maybe 7500 miles. Use stock 820s filter
I use Mobil one full synth; Mobil is very good at cleaning carbon deposits.
Adding a little atf or marvel mystery oil with each change can restore your oil pressure.
We had a 5.0 w 275k miles on it, ran good! Changed the transmission and then the engine would start to lose oil
Pressure at idle. Added mechanical gauge, the truck would drop to zero!!! Tick tick tick
Started using diesel oil instead of conventional changed it weekly… truck was driven daily.. soon oil pressure returned then we switched to Mobil one and some marvel for a few changes… last I heard that truck is still on the road no more low pressure issues because we effectively cleaned out the carbon bits that are
Plugging your drain back holes and oil pressure passages

 

[dvdswan]

What did the oil look like when you last changed it? Since you have a mech. oil gauge, you should see 10 psi per 1k rpm. At idle I would think 20 psi would be more like a clean engine.

I would do what @410Fortune mentioned and do this. Your oil should not be black when its changed, but a light brown. Black you have dirty passages and more possibilities of sludge.

 

[Jeff213]

What did the oil look like when you last changed it? Since you have a mech. oil gauge, you should see 10 psi per 1k rpm. At idle I would think 20 psi would be more like a clean engine.

I would do what @410Fortune mentioned and do this. Your oil should not be black when its changed, but a light brown. Black you have dirty passages and more possibilities of sludge.

it is light brown now after driving from TN to CA towing a camper.

When I had 5w30 in it the oil pressure indicator would flicker at high rpm and at idle, when I put in the shell rotella 15w40 it stopped flickering at high rpm, just at hot idle, especially at high elevation, which it idles lower at high elevation due to less o2

I put sea foam in the crank case in TN and drove 150 miles and the oil was still clean when I drained it and put new oil in. I put shell rotella 15w40 in it. It has never been black, I have always used synthetic oil, so right now it has shell rotella with about 3000 or so miles on it.

Oil level is spot on, it doesn't really use much oil at all, maybe a quart of oil in 5000 miles.

I got the oil pressure sending unit at auto zone so hopefully that is the problem I will try a motorcraft one.

 

[dvdswan]

Did you have this issue with the 15w40 as well? What does the owner's manual recommend for oil?

 

[Jeff213]

Did you have this issue with the 15w40 as well? What does the owner's manual recommend for oil?

owners manual indicates 5w30, I have always used full synthetic, usually mobil one. I still have the issue of it flickering with the shell rotella 15w40, I will try a motorcraft sending unit instead of the duralast one.

 

[CDW6212R]

The oil thickness is the viscosity figure at the end, the 30, or 40. The first number only affects start up cold running, choose that by your climate when you start the car.

So 40 is thicker, it will resist imperceptibly more than the 30, the oil pressure will go up by an unmeasurable amount(your cheap gauge of any brand). The fact it did help with the light coming on at high rpm, says the 30 weight was a little thinner while running normal temps.

For an engine with no known issues, most oils with a 20-40 running weight will work fine. Only when there is an issue, you think more about the viscosity choice. Usually that means going a little thicker, and that isn't a magic fix.

It sounds like the oil pressure sensor is suspect, hopefully it is the problem, not wear of the oil pump or a plugged pickup screen. You are already using very good oil, continue and move on to something else.



The typical low oil problem with an engine is bad maintenance, poor oil quality by the first owner. If they neglect to change the oil properly(synthetic and don't let it go too long), then it increases wear plus accumulates sludge throughout. Worst case is to have sludge build up at the pickup screen, not in any oil passages. The passages are not impossible to plug, but they never do, the screen does often plug up. That starves the oil pump, pressure drops, and soon the bearings are scored. If oil pressure dropped at all with thicker oil, then that could point to a blockage such as the pickup screen, and thicker oil makes it worse.

 

[Jeff213]

I put in a motorcraft oil pressure switch and drove the truck a few times, no bouncing pressure gauge at idle anymore. Truck still sounds great. Hopefully that was it!

I think the issue was a chinesium sending unit from auto zone. Don't cheap out on the sending unit.