bad oil pump symptoms?

[bmxryder]

Hey guys, I'm having a little problem with my truck.

When I rev the motor to around 3 grand (guessing since I don't have a tach) my oil pressure starts going down. My truck has almost 200k miles on it and I've heard the worn out motor may have something to do with it, but an oil pump sounds more reasonable. Any advise?

Thanks!

 

[ForOffRoadDriving]

have you checked it with a mechanical gauge to confim that the pressure is actually dropping? our stock gauges arent worth a broke dick as mine reads on the lower portion of the pressure scale but my autometer says i have a healthy 60psi. with 200,000 it is also likely that your bearing tolerances have increased and you may indeed have low pressure, but a new pump may not cure your issue. how regular have you been with oil changes? its possible that your pickup screen may be partially plugged or blocked by sludge but the only way to be sure of that is to drop the pan.

 

[bmxryder]

No I havent checked it with a mechanical gauge, is it easy to hook up?

I change my oil regularly and once this started happening I changed it again. Since it suddenly started happening a clogged tube sounds reasonable. Where can I find the pick up tube?

 

[snoopdoggie]

Try a couple things. Start it "cold" and see if you get the same drop while it is cold. When you do experience the drop shut it down and wait about a min then restart and rev it and see if the drop returns right away or is delayed. I had a 2.3 with a clogged pickup tube and this is a couple things I did to help diagnose it. I put a mechanical gauge in and ran down the road. Not at any kind of speed, maybe 25mph. When the motor warmed up, and tolerances increased allowing more pressure loss, the pressure dropped low. I could turned it off for a little, 30 to 60 seconds and restart and have full pressure again. It was definitively a clogged screen. It was so bad I was surprised any oil would get through it. Just a few thoughts for you.

 

[AllanD]

MY vote is a clogged pickup.

I've yet to either see or hear a credible report of an actaul "Bad oil pump" on 4.0.

The 4.0 engine is something os a sludge maker.

MY first advice is to get yourself a large (quart) bottle of Marvel
Mystery oil when the engine is warm and go for a drive. then
while the engine is still HOT drain the oil and change the filter.

Marvel Mystery oil seems to dissolve the goo that builds up inside the engine.

Be aware after adding this stuff you could easily make it worse as it
dislodges more crap from inside the engine and that stuff only has
one place to go... down into the sump where it can plug the pickup
even more.

The 4.0 engine is pretty forgiving of running with a plugged pickup and
loss of oil pressure we aquired an aerostar with that exact problem
removed and washed out the pan and pickup and then ran the thing for
another six years. (And two more A4LD's

BTW, after washing it out switch to Mobil1

I have found overthe years that the stuff that collects inside the
engine that MMO can't wash out will gradually be removed by Mobil1
it's distressing to see $30 worth of synthetic oil turn black
but it is far cheaper than buying another engine.


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