1991 Oil Pressure

[auburn56]

Easy question for the experts, when i start up my explorer the gauge goes to 30 psi and then settles down to about 12 psi. What is normal for these engines and is there anything i can do about it? Thanks in advance for any help.

Dan

 

[Maniak]

What are you using to check the oil pressure?

The factory oil gauge is just an analog idiot light (search for fake oil pressure on this site)... Over 5psi shows normal.. < 5psi or so shows low...

Now.. assuming you are using some aftermarket gauge, and it is reading acurately, you do have some low oil pressure..

Cold (cool) start is normally 40psi or higher... Once it is warmed up some (not hot) you should be 40psi or higher at 2000 rpms... As it gets hotter, your idle oil pressure may be low, but the 2000 rpms should stay above 40.

Low oil pressure can be the oil pump (bad bypass spring, clogged screen or just a bad pump).. It can also be too thin of oil (5w-30 gives our '92 oil pressure lower than I like, so I run 15-40 synthetic at least during the summer here in southern Arizona)..

Another posibility is worn bearings OR exsessive(sp?) clearence between the pushrods and the rockers..

Bad oil pump or byapass spring in the oil pump is a bad thing.. You can't get to it w/out dropping the pan, and you can't drop the pan w/out pulling the motor. If the screen is dirty one of those flushes that runs the oil backwards might help.. I've also heard of people using bent coat hanger type material through one of the holes in the oil pan to scrape the oil pickup screen.

worn bearings is another rebuild motor time item..

Excessive clearance for the pushrods can be fixed.. You can change the pushrods and rockers w/out rebuilding the motor.. But some people say don't change the pushrods w/out changing the rockers and lifters and cam..

Thicker oil may also help, at least "mask" the issue..

I'm sure you will get other ideas too..

~Mark

 

[Papa]

Welcome to the site. Maniak did a nice job of covering the bases. The things that can really help when answering your questions are the details about how many miles, what kind of oil/weight, do you hear any sounds like piston slap or light tapping of any kind and anything else you can include.

 

[auburn56]

Thanks for the idea's. When the engine is cold and first started up, the pressure is 30psi. I am using an actual gauge to measure the pressure. The pressure then will drop down to around 13 and go up to 20psi when the rpm's are above 2000. I have been working on the engine, Timing chain and gears and reinstalling the front cover and i am wondering if some old sealing or gasket material dropped in the pan and was picked up at the screen. I also have tappet noise, but have already replaced the tappets and pushrod/rocker arms. The engine has 100k miles and i use 10-30 oil. Thanks again for you help.

Dan

 

[shamaal]

FWIW
According to Haynes oil pressure at 2000 rpm with engine hot is 40 to 60 psi

 

[Maniak]

That oil pressure does sound low...

It may be worth it to have one of those places to the engine flush (when they push the oil backwards through the engine) to try to clean up things.. I've never done it, but I've "heard" it works.

The only things I've ever done for low pressure in our X is put in marvel mystery oil in the oil before I do an oil change.. Change it when its hot, and use slightly thicker oil (I use 15-40 synthetic).

I was going to attempt to "scrape" the screen if the oil pressure stayed low, but after the last oil change (marvel mystery and slightly thicker oil) my oil pressure came back up to where I like it.
It was sitting at 40-45 at 2000rpms when hot.. which isn't exactly bad, but it was lower than it used to be which bothered me.

~Mark