2002 Mercury Marquis oil pressure

This could be a few things, but I am going to start with where I feel the problem may be. I need you to remove the valve covers and check to see if the drain ports are plugged in the heads. If they are, oil can't return to the oil pan fast enough. If it isn't that, you may have a partially plugged oil pump screen. That will require that you remove the oil pan,

Before doing anything, make sure the oil is clean and full.

Let me know what you find.

JUST TO SORTA BUILD ON WHAT J and N SAID

BEFORE YOU SNATCH OFF THE VALVE COVERS,

........SOMETIMES YOU CAN TAKE OFF THE OIL FILL CAP OR REMOVE GROMMETS IN THE VALVE COVERS (MAYBE JUST ONE SIDE AIN'T DRAININ' BACK).....WITH A FLASHLIGHT YOU MIGHT BE ABLE TO SEE OIL SLOWLY BUILDING UP IN THE COVER(S) WHILE THE ENGINE RUNS

IF YOU SEE IT SLOWLY "FILLING UP" WITH OIL, PRETTY MUCH FOR SURE, THE DRAIN PORTS IN THE HEAD ARE STOPPED/ OR PARTIALLY STOPPED UP

THIS MAY BE HARDENED OIL SLUDGE....I'VE ALSO SEEN THE "FOIL" SEAL TORN OFF, FROM A OIL BOTTLE/ OR AN ADDITIVE THAT WAS POURED INTO THE ENGINE, CLOGGING UP THE DRAIN HOLE

THESE PORTS CAN BE EZily UNSTOPPED WITH A WIRE/ WELDING ROD/ ETC, WHEN YOU REMOVE THE VALVE COVERS

IN SIMPLE TERMS.....THE OIL RESERVE IN THE PAN, GETS PUMPED UP INTO THE VALVE COVERS FASTER THAN THE OIL CAN RETURN BACK TO THE PAN....MR. PAN GOES DRY, OIL PRESSURE GOES AWAY, VITAL ENGINE PARTS (BEARINGS) STARVE FOR LUBRICATION

ALL PARTS NEED LUBRICATION.....AND THE VALVE TRAIN IS REALLY GETTING MORE THAN IT'S FAIR SHARE......IT'S THE MAIN AND ROD BEARINGS IN THE BLOCK THAT SUFFER, IF THIS IS THE CONDITION YOU HAVE

CONTINUING TO RUN IT, WILL SURELY CAUSE TERRIBLE DAMAGE TO THE HEART OF YOUR ENGINE.......HOPEFULLY YOU HAVE NOT ALREADY GOT TO THAT POINT YET

FOR MORE GOOD INFO....YOU MIGHT VISIT AN AUTOMOTIVE MACHINE SHOP.....HE MIGHT HAVE A SET OF HEADS LIKE YOURS SITTING THERE LOOKING LIKE BRAND NEW..........THIS MIGHT LET YOU SEE HOW BIG THE DRAIN HOLES ARE, SO YOU CAN INSURE YOU GET YOURS COMPLETELY UNSTOPPED.......SOMETIMES THE GOO AND HARD DEPOSITS WILL FOOL YOU AS TO WHAT IS "METAL" AND WHAT SHOULD BE REMOVED

JUST A THOUGHT

LET US KNOW WHAT YOU GOT GOING ON

THE MEDIC

I looked in valve covers with engine running. I did not see any oil build up in the valve covers. So do you think it might be the screen or something else.

'FORE YOU DO ALL OF THAT

WHY DON'T YOU TRY THIS FIRST-US!.....

REMOVE YOUR OIL PRESSURE SENDER AND INSTALL A MECHANICAL OIL PRESSURE GAUGE---THIS WILL GIVE YOU A REAL ACCURATE READING AS TO WHAT YOUR ACTUAL OIL PRESSURE IS, AND IS DOING WHILE BEING DRIVEN.

A GAUGE SET UP SORTA LIKE MINE, OR AN AFTERMARKET UNDER THE DASH MOUNT (USED AS A PORTABLE, TEMPORARY TEST PLATFORM) THESE USUALLY COME WITH A LONG PLASTIC LINE THAT WILL ALLOW IT TO BE RUN OUT FROM UNDER THE HOOD AND INTO YOUR WINDOW, SO YOU CAN WATCH IT AS YOU DRIVE, ON TOP OF THE DASH, OR IN THE SEAT BESIDE YOU.....MIGHT PICK OUT A PERTTY ONE, YOU MAY WANT TO MOUNT IT PERMANENTLY AND DO AWAY WITH THE ELECTRIC ONE!....THEN RUN THE LINE THRU THE FIREWALL TO MAKE IT ALL NEAT

IF IT SAYS EVERYTHING IS A-OKAY WITH THE MECHANICAL GAUGE

THEN MOST LIKELY YOUR SENDER IS DEFECTIVE (NORMALLY THE PROBLEM IN CASES LIKE YOURS)--- THE ACTUAL GAUGE IN THE DASH WOULD BE THE SECOND GUESS AS TO BEING BAD, OR THE WIRING IN BETWEEN

SOME PEOPLE JUST CHANGE THE SENDER AS THEIR "TEST", THAT IS FINE, UNLESS IT DOES NOT SEEM TO WORK OUT

I LIKE TO KNOW WHAT THE "REAL DEAL IS", BEFORE I BUY A PART....I CAN'T AFFORD A NEW ENGINE EITHER.......PARTS CHANGING IS KINDA A WEIGH IT OUT THING $$$/ TIME/ SATISFACTION WITH RESULTS.....OR YOU NOW HAVE A WORKING OLD SPARE PART!......IN OTHER WORDS I LIKE "ACCURATE NUMBERS" OVER ELECTRICALLY GENERATED NUMBERS.....MY PERMANENT OIL PRESSURE GAUGES ARE MECHANICAL.............I LOVE GAUGES FOR EVERYTHING!

KEEP US POSTED

THE MEDIC

Since you are hearing knocking when the pressure drops, either you have a screen on the oil pump that is plugging or the pump is going bad.