1994 Jeep Cherokee Low oil pressure

JAMIELEEGAUTHIER

MEMBER
1994 JEEP CHEROKEE
6 CYL
4WD
AUTOMATIC
273,500 MILES

Hi guys. Ok I am a mechanic myself but seem to be stumped on this one. My inline 6 4.0L was having low oil pressure and bearing noise. I replaced all the top end and bottom end including oil pump. I did notice though that there is a hole behind the cam sprocket that you can see a push rod. First thing is would this hole there about a nickel size cause my low oil pressure? The engine now has no noise since it is all new. Also I don't burn a drop of oild between oil changes and don't burn any antifreeze either. When I first start up it is sitting at 20-30 and than when it warms up it drops to 4 lbs. I am using 10W30 pennzoil. Any help on this would be appreciated as I don't want to drive it with the low oil and blow out my bearings. When you step on it the oil pressure goes up to 20 lbs or more. HELP! I am completely at a loss. Thanks in advance for any help here. Oh yeah I am using a mechanical gauge for the reading also.

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

CAUSES OF LOW OIL PRESSURE

Possible culprits include:

Excessive main and rod bearing clearances (someone may have installed the wrong-sized bearings or standard-sized bearings on a reground crankshaft). Only 0.001-inch of extra clearance in the main bearings can reduce oil pressure up to 20 percent!

Excessive camshaft bearing clearances (a bearing may have slipped out of place when the cam was installed).

Excessive clearances inside the oil pump.

Leaks between the oil pump and engine.

Oil pump relief valve stuck open or installed backward.

A loose or mispositioned oil pickup tube (too high in oil pan).

A defective oil pressure sending unit or oil pressure gauge.

Low oil level in the oil pan.

Cracks or leaks in the oil galleries or gallery plugs.

Cracked oil pump housing (improper installation).

Oil viscosity too thin for hot weather.