Mechanics

WHY DOES MY OIL PRESSURE DROP WHEN I COME TO A STOP AND THEN GO BACK TO NORMAL WHEN I DRIVE OFF?

1999 Jeep Grand Cherokee • 160,000 miles

When I come to a stop the oIl pressure goes down to almost nothing and the red check gauges light comes on. Once I drive off, the check gauges light goes off and the oil pressure goes back to normal. As I speed up and slow down, the oil pressure goes up and down accordingly. I had the oil changed immediately and it's still doing this. They used 5w 30 synthetic blend oil. Any thoughts or suggestions?
Avatar
Steven W. Cannedy
December 10, 2011.



Because the oil pump is engine driven. As the engine speed goes down, the oil pump output pressure decreases. The oil pressure should not drop below about 20PSI. You should hook up a dependable oil pressure gauge and see what pressure is developed at idle.


Rivermikerat
Dec 10, 2011.
SUMPIN' LIKE MINE

EVEN ONE OF THOSE UNDER DASH UNITS WILL WORK FOR TESTING, MOUNT IT PERMANENTLY LATER, OR KEEP USING IT AS A TESTER

A MECHANICAL GAUGE WILL GIVE YOU A TRUER READING, AS COMPARED W/ AN ELECTRIC GAUGE

IF THE MECHANICAL GAUGE IS TELLIN' YOU EVERYTHING IS A-OK, AT ALL RPMS

THEN YOUR OIL SENDING UNIT ON THE ENGINE IS PROBABLY (MOST LIKELY) THE PROBLEM----BUT NOT COMPLETELY RULING OUT A GAUGE PROBLEM (SELDOM)

KEEP US INFORMED

THE MEDIC


Tiny
CJ MEDEVAC
Dec 11, 2011.
That is just normal pressure changes that happens in all vehicles as long as it is not dropping low enough to put the warning light on.


Wrenchtech
Dec 11, 2011.
It is dropping to almost zero, Wrenchtech. A bit too far.


Rivermikerat
Dec 11, 2011.
The right way to check it would be with a manual gauge but the price of a new sender may make it cheaper to just trying a new sender instead.


Wrenchtech
Dec 11, 2011.
Eh, I don't like most stock gauges. I prefer a decent mechanical gauge from Sun-Pro. Borg-Warner or Autometer would be the best.


Rivermikerat
Dec 11, 2011.
Come on, you're stuck in the 60's. LOL


Wrenchtech
Dec 11, 2011.
Nope. Unless they're on something like a performance vehicle, stock gauges are usually unreliable.


Rivermikerat
Dec 11, 2011.
That hasn't been my experience. Maybe on a racing engine.


Wrenchtech
Dec 11, 2011.
WHEN YOU ARE "AS ONE", WITH YOUR "REAL" VEHICLE

ONE CAN SENSE AN ABNORMALITY

AND NEVER EVEN LOOK AT THE GAUGES!

THE MEDIC


Tiny
CJ MEDEVAC
Dec 11, 2011.
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