The oil pressure gauge goes to 0 psi when I stop in a light. Is it oil pump, electrical, a gasket?

LOVEMCFLURRY8

MEMBER
1996 JEEP GRAND CHEROKEE
165,000 MILES

Hi) I own a 96 Jeep Grand Cherokee 6-cylinder 4L 165,000 miles. The oil pressure gauge goes to 0 psi when I brake and back to 40 psi when I accelerate. Upon first turning on the engine the psi goes up to 40 psi then after 8 minutes or so it starts going down to 0 psi when stopping on a light. Sometimes when I go below 10 mph the vehicle stals the Rpm goes up the mph slowly goes up after 6 seconds to normal wanted speed. The miles ran odometer (165,000) is hard to read but functioning. Two days ago the Starter failed. I changed the oil filter, fuel filter, oil 10w30, the oil gauge switch located near the oil filter. The oil level is good. Are the issues related? Will replacing the the Instrument Gauge Cluster help with the gauge issue?What type of oil is recommended I live in LA? Is it electrical or oil pump or gasket problem? How much would labor cost roughly for each? Theres no unusual engine loud noices while driving. The fuel filter I rescently changed was really dirty. I would appreciate your expert opinion. Than you!

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

The place to start is by having the actual oil pressure checked with a mechanical gauge. There were some problems with the sending units in the mid '90s, and they would cause what you're describing, but if you already replaced it, that would have solved the problem. To double-check, there should be two terminals in the old sending unit. One is for the gauge and one is for the warning light. If yours just had one terminal, you might have replaced the wrong one. Look for a second one in the same area.

If the pressure really is low once the oil gets hot and thins out, it's usually due to worn engine bearings. Oil is still getting to them and doing what oil is supposed to do, (isolate moving parts from each other), but it's running out too easily. It very likely is still possible to have new bearings installed without having to do any other major engine work. Once the knocking starts, the crankshaft will usually be damaged and need to be replaced. At the very least that requires removing the engine.

The owner's manual will list the oil viscosity recommended for the temperatures in your area. A higher viscosity might bring the pressure up a little. I have an old rusty trusty '88 Grand Caravan with almost 400,000 miles and I've been running the cheapest 10W-40 I can find for many years. It originally called for 10W-30 which is a little thinner. Even the cheapest oil is made by a name brand manufacturer. It's just packaged for other retailers. All oil is much better than what we had available a few years ago. The detergents and other additives are also much better.