Crappy oil pressure

182,000 on my '89 XJ. I know there have been a million threads on this, but can I trust my stock oil pressure guage? When I start the engine cold, the pressure runs at 40 psi +, but after the engine warms up, it runs at about 10 psi if I at idle or doing 70mph. Do I need a new oil pump?

If your power is fine and you don't experience any strange engine noise, everything is fine.....probably just an oil pressure sensor gone bad, about a 5 minute job to replace......right above the oil filter.

I'm on my second sending unit in about 1000 miles. First one went bad right away (showed oil pressure as maxed). This one hasn't done that yet it seems...

Mine shows WAY over max when cold in the winter......it's just the gauge tho, so I don't care

When warm it shows normal readings. Or when the oil is warm, in the winter too.....just takes some time for a normal reading to be shown.

Ahhhhh gauges.....pfffffftttt who needs em....my ears tell me if anythings wrong with the 4.0

heyjpark1 said:

182,000 on my '89 XJ. I know there have been a million threads on this, but can I trust my stock oil pressure guage? When I start the engine cold, the pressure runs at 40 psi +, but after the engine warms up, it runs at about 10 psi if I at idle or doing 70mph. Do I need a new oil pump?

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You've come to the right place 'cause it looks like your engine is sick and needs a doctor's attention. Here's what you need to do and don't delay. The life of your engine depends on it :

1. Verify the dash gauge oil pressure readings with a mechanical gauge. If the mechanical gauge shows different readings, change your gauge sending unit (again). If the readings are the same, you have a serious low oil pressure problem.

2. If oil pressure really IS low, pull the oil pan. There's a fair chance your oil pump is worn out so replace it with a new OEM pump and pick-up. A high volume pump is overkill.

3. While you're there, replace the rear main crank oil seal 'cause if it's still the original 182k mile old unit, it'll leak soon if it isn't already.

4. Replace all the rod and main bearings. The chances are that they'll be worn and if you don't replace them, you could still have a low oil pressure even with a new oil pump and you'll be kicking yourself for not replacing the bearings.

5. Clean the inside of the oil pan thoroughly before you bolt it back on. You don't want any dirt clogging up the pick up screen of your brand new pump.

Thanks, Doc. Will replacing the main bearings help if the crank is worn?

If the crank journals show signs of scoring or have grooves deep enough to catch a finger nail, you'll need to have the journals reground undersize and fit undersize bearings to match.

THE FIRST QUESTION should always be, what brand oil filter do you have ?

Hmmmm.never thought about that...got a cheap piece o' sheet.

Fram's are known not to hold pressure when the oil pump is off......that's why its never recommended to pound on the engine when it's first started (give it some time to idle).

However, once the pump is running and oil is flowing, the filter shouldn't affect oil pressure....unless it is clogged.