oil pressure light

fatngs · #1 (**permalink**) 10-03-09, 04:52 PM

here's my new problem of the day!

i was sitting at a traffic light when i noticed the oil light was on; however it wasnt steady, it couldnt decide whether it wanted to be on or off completely

as soon as i gave the engine some revs it stayed off

so i made the turn and pulled over and shut the engine off

the oil was low a quart (go figure, my engine LOVES oil) but i was able to make it home without the light coming back on; i added a quart as soon as i got home

could this be a major problem or did the engine just need more oil?

another question is what type of oil is best for my engine? the oil cap, owners manual, haynes manual, ect all say it prefers 10W30; everytime i get my oil changed they use 5W30; could this be an issue?

submariner409 · #2 (**permalink**) 10-03-09, 05:32 PM

Some Northstar installations seem to have problems with the oil pressure sending switch in the top side of the oil filter adapter. The GM spec for low level light is about 5 psi, but some trip at higher pressures. Replace the sender and also change to your favorite brand of oil in the viscosity range recommended for your car.

May I suggest that for your engine, which uses flat-tappet hydraulic cam followers, you use a marine or fleet oil in 10W-30. Why? Because these HD oils have a higher ZDDP (Zinc-Phosphorus) anti-scuff additive package than current SL or SM Starburst "energy conserving" oils. Shell Rotella, Chevron DELO, Pennzoil Long Life are some examples of HD fleet oils. Very good for older hydraulic tappet and OHC tappet engines.

Freakzilla · #3 (**permalink**) 10-03-09, 06:59 PM

Does that apply to the 4.9L engine too? Does it have the same lifters?

I had the Low Oil Pressure warning message for a while, the first time it was actually low but I kept getting it. Changing the sensor seems to have fixed it.

**Ranger** · #4 (**permalink**) 10-03-09, 10:20 PM

Yes it does. The 4.9's and pre 2000 Northstars require 10W30.

No 5W30. I still use 10W30.

fatngs · #5 (**permalink**) 10-07-09, 01:03 PM

it did it again today! i was at school and i parked; when the engine was at 600 RPM's the oil light was flashing, but when i revved it a little it turned off

when i got done my first class i went to my car and checked the oil level and it's full

Freakzilla · #6 (**permalink**) 10-07-09, 02:52 PM

Did you try changing the sensor? If it's not that, might be the oil pump. Changing that requires removing the crossover exhaust pipe. If it's not that, might be your bearings.

submariner409 · #7 (**permalink**) 10-07-09, 03:02 PM

Change your oil and filter and use a good 10W-30 High Mileage or Truck and SUV oil with a WIX 51522 filter. Change the oil pressure sending switch/unit/sensor, located at the top side of the oil filter adapter, at the same time. It may be easier to remove the entire adapter (2 bolts) in order to replace the switch and adapter O-rings on the bench.

When you do the oil change, use the recommended 7.5 quarts with filter and you'll notice that the correct full mark is halfway up the dipstick hashmark.

He has a Northstar 4.6 and his oil pump is inside the front chaincase, wrapped around the crankshaft nose.

SIrnoah · #8 (**permalink**) 10-07-09, 03:10 PM

I am having a similar problem. I just rebuilt my 87 4.1 engine. New oil pump, new lifters, heads redone, new cam, etc. Car runs and sounds good, but at idle the oil pressure light comes on and when checking with a outboard gauge the oil pressure is near zero.

I am baffled as to what the problem is. There is no ticking, or other noise.

Please help I am desperate at this time. This is my first rebuild and I am running out of Money.

submariner409 · #9 (**permalink**) 10-07-09, 03:13 PM

If you replaced the oil pump there's a chance that there's an air leak in the pump pickup tube, you left out an oil gallery plug somewhere, or "replaced the cam" .......... did you install and bore new cam bearings ?

ANY GM engine should have at least 10 psi oil pressure, hot idle.

If you have near zero pressure at the oil pressure sending unit I hate to say it, but you got big problems.

SIrnoah · #10 (**permalink**) 10-07-09, 06:28 PM

New bearings yes. Pressure is ok at speed, but very low at idle. Could idel be set too low? What else should I look at?

submariner409 · #11 (**permalink**) 10-07-09, 07:46 PM

Idle 650 - 700 hot in gear.

Dave S Texas · #12 (**permalink**) 10-07-09, 09:05 PM

The 4.1 oil-pressure switch opens at 4psi/above with correct idle RPM.

fatngs · #13 (**permalink**) 10-10-09, 11:53 AM

i replaced the oil sending unit; right after, about 15 min after driving it did it again only the oil light would come on at anything under 1000 rpm

i was on my way to a doctor's appointment so i had to keep going; i pretty much braked with my left foot and kept my right foot on the gas to keep the revs up

however, on the way back it was fine and havent had the problem since

also i havent changed the oil yet

Hipoint · #14 (**permalink**) 10-10-09, 01:36 PM

Things sure have improved since I used to work on these puppies... Haven't seen "STP" mentioned once!

submariner409 · #15 (**permalink**) 10-10-09, 06:44 PM

STP probably ruined more engines than it helped. I hope NASCAR fans didn't really believe that Cale was actually running that stuff in his car.........