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

  • Tiny
  • Steven W. Cannedy
  • 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?

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Saturday, December 10th, 2011 AT 8:53 PM

20 Replies

  • Tiny
  • rivermikerat
  • Member

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.

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Saturday, December 10th, 2011 AT 8:58 PM
  • Tiny
  • CJ MEDEVAC
  • Expert
  • 9,227 posts

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

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Sunday, December 11th, 2011 AT 3:42 AM
  • Tiny
  • Wrenchtech
  • Expert
  • 20,039 posts

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.

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Sunday, December 11th, 2011 AT 4:11 AM
  • Tiny
  • rivermikerat
  • Member

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

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Sunday, December 11th, 2011 AT 4:58 AM
  • Tiny
  • Wrenchtech
  • Expert
  • 20,039 posts

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.

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Sunday, December 11th, 2011 AT 2:01 PM
  • Tiny
  • rivermikerat
  • Member

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.

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Sunday, December 11th, 2011 AT 9:47 PM
  • Tiny
  • Wrenchtech
  • Expert
  • 20,039 posts

Come on, you're stuck in the 60's. LOL

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Sunday, December 11th, 2011 AT 9:50 PM
  • Tiny
  • rivermikerat
  • Member

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

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Sunday, December 11th, 2011 AT 10:15 PM
  • Tiny
  • Wrenchtech
  • Expert
  • 20,039 posts

That hasn't been my experience. Maybe on a racing engine.

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Sunday, December 11th, 2011 AT 10:22 PM
  • Tiny
  • CJ MEDEVAC
  • Expert
  • 9,227 posts

WHEN YOU ARE "AS ONE", WITH YOUR "REAL" VEHICLE

ONE CAN SENSE AN ABNORMALITY

AND NEVER EVEN LOOK AT THE GAUGES!

THE MEDIC

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Sunday, December 11th, 2011 AT 10:36 PM

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