Pump or bearings? Oil is slow to pump up pressure so it rattles a few seconds.

[moparman12]

The dash gauges aren't working to well (intermittent or not at all) so I just installed a premium Autometer oil pressure gauge under the hood temporarily to make sure it wasn't running really low pressure after it warms up. Cold start pressure is 45ish at idle and above 1200 runs up to 55 before the pressure relief valve kicks in. When it is fully warmed up, it still will go to 55, but at a slow idle, pressure is 18-20.
The 4.0 engine in an 88 Cherokee had sat for over 7 months and, when I started it finally, it didn't pick up the oil, so after a minute or so I finally shut it down and pulled the distributor and used a tool I made to spin the pump and finally got oil pressure. The engine runs smooth and strong as does the transmission and everything works great, except the thing rattles as soon as I start it for 1-3 seconds, and only after it has sat for more than a few hours.

Sooo..I guess it likely isn't the pump, since it pressurizes the system fine when hot. Maybe I damaged the bearings running it as long as I did without decent pressure???

How hard is it to pull the pan and access the rods and mains while the engine is still in the Jeep?

 

[SteelHeadz]

REMOVAL

1. Disconnect negative cable from battery.
2. Raise the vehicle.
3. Remove the oil pan drain plug and drain the engine oil.
4. Disconnect the exhaust pipe at the exhaust manifold.
5. Disconnect the exhaust hanger at the catalytic converter and lower the pipe.
6. Remove the starter motor.
7. Remove the engine flywheel and transmission torque converter housing access cover.
8. If equipped with an oil level sensor, disconnect the sensor.
9. Position a jack stand directly under the engine vibration damper.
10. Place a piece of wood (2 x 2) between the jack stand and the engine vibration damper.
11. Remove the engine mount through bolts.
12. Using the jack stand, raise the engine until adequate clearance is obtained to remove the oil pan.
13. Remove the oil pan bolts. Carefully slide the oil pan and gasket to the rear. If equipped with an oil level sensor, take care not to damage the sensor.

INSTALLATION

1. Clean the block and pan gasket surfaces.
2. Fabricate 4 alignment dowels from 1 1/2 x 1/4 inch bolts. Cut the head off the bolts and cut a slot into the top of the dowel. This will allow easier installation and removal with a screwdriver .Install two dowels in the timing case cover. Install the other two dowels in the cylinder block .Slide the one-piece gasket over the dowels and onto the block and timing case cover.
3. Position the oil pan over the dowels and onto the gasket. If equipped with an oil level sensor, take care not to damage the sensor.
4. Install the 1/4 inch oil pan bolts. Tighten these bolts to 9.5 N·m (84 in. lbs.) torque. Install the 5/16 inch oil pan bolts .Tighten these bolts to 15 N·m (132 in. lbs.) torque.
5. Remove the dowels. Install the remaining 1/4 inch oil pan bolts. Tighten these bolts to 9.5 N·m (84 in. lbs.) torque.
6. Lower the engine until it is properly located on the engine mounts.
7. Install the through bolts and tighten the nuts.
8. Lower the jack stand and remove the piece of wood.
9. Install the engine flywheel and transmission torque converter housing access cover.
10. Install the engine starter motor.
11. Connect the exhaust pipe to the hanger and to the engine exhaust manifold.
12. Install the oil pan drain plug . Tighten the plug to 34 N·m (25 ft. lbs.) torque.
13. Lower the vehicle.
14. Connect negative cable to battery.
15. Fill the oil pan with engine oil to the specified level

OIL PUMP PRESSURE

The MINIMUM oil pump pressure is 89.6 kPa (13 psi) at 600 rpm. The NORMAL oil pump pressure is 517 kPa (75 psi) at 1600 rpm or more.

4.0L ENGINE SPECIFICATIONS

Camshaft Hydraulic Tappet ClearanceZero Lash Bearing Clearance0.025 to 0.076 mm (0.001 to 0.003 in.) Bearing Journal Diameter No. 151.54 to 51.56 mm (2.029 to 2.030 in.) No. 251.28 to 51.31 mm (2.019 to 2.020 in.) No. 351.03 to 51.05 mm (2.009 to 2.010 in.) No. 450.78 to 50.80 mm (1.999 to 2.000 in.) Base Circle Runout0.03 mm - max. (0.001 in. - max.) Valve Lift10.29 mm (0.405 in.) Intake Valve Timing Opens12.4° BTDC Closes60.9° ABDC Exhaust Valve Timing Opens49.8 BBDC Closes29.2° ATDC Valve Overlap42.6° Intake Duration253.3° Exhaust Duration259.° Crankshaft End Play0.038 to 0.165 mm (0.0015 to 0.0065 in.) Main Bearing Journal Diameter No. 1-663.489 to 63.502 mm (2.4996 to 2.5001 in.) Main Bearing Journal Diameter No. 763.449 to 63.487 mm (2.4980 to 2.4995 in.) Main Bearing Journal Width No. 127.58 to 27.89 mm (1.086 to 1.098 in.) Main Bearing Journal Width No. 332.28 to 32.33 mm (1.271 to 1.273 in.) Main Bearing Journal Width No. 2-4-5-6-730.02 to 30.18 mm (1.182 to 1.188 in.) Main Bearing Clearance0.03 to 0.06 mm(0.001 to 0.0025 in.) Main Bearing Clearance (Preferred)0.051 mm (0.002 in.) Connecting Rod Journal Diameter53.17 to 53.23 mm (2.0934 to 2.0955 in.) Connecting Rod Journal Width27.18 to 27.33 mm (1.070 to 1.076 in.) Out-of-Round (Max. All Journals)0.013 mm (0.0005 in.) Taper (Max. - All Journals)0.013 mm (0.0005 in.) Cylinder Block Deck Height240.03 to 240.18 mm (9.450 to 9.456 in.) Deck Clearance (Below Block)0.546 mm (0.0215 in.) Cylinder Bore Diameter - Standard98.45 to 98.48 mm (3.8759 to 3.8775 in.) Cylinder Bore Diameter - Taper (Max.)0.025 mm (0.001 in.) Cylinder Bore Diameter - Out-of-Round0.025 mm (0.001 in.) Tappet Bore Diameter23.000 to 23.025 mm (0.9055 to 0.9065 in.) Flatness0.03 mm per 25 mm (0.001 in. per 1 in.) Flatness

 

[moparman12]

Wow...Thanks! Great info.
Looks like I'll be doing some bearing checks soon.