Topic: 20 psi at Idle

[Jeeplander]

Hey, I have a low idle oil pressure  with 10w30 (13psi), I swapped out oil for 10w40 and hot idle pressure is 20'ish. Engine purrs....even did with the 10w30. I run a Mech. oil guage. I'm hunting this weekend, so i will be running 4hi and high rpms........  Should I be worried???

[dwtaylorpdx]

Low oil pressure is usually a sign that the rod and or main bearings are getting tired.

I'd bump up to 20w50 and start planning the rebuild...

Dave

[Jeffy]

You should really make sure the sender is working right.

[sharpxmen]

You should really make sure the sender is working right.

he's got a mechanical gauge so that's not it

FSM specifies the minimum (safe) operating pressure to be 13psi at 600 rpm

normal idle pressure at 800 rpm per FSM is 25 to 35 psi, on mine it always ran at about 30 to 35 at idle with engine well warmed running Mobil 1 10w40
max pressure is 75 psi (relief valve pressure)
over 1600 rpm is supposed to be min 37 psi oil pressure

[Jeeplander]

just to note, oil pressure is normal while driving, never below 35psi........

[Jeffy]

Whoops, missed that.

[Jeeplander]

If I go to replace the bearings, how do I know in advance what size to get?

[sharpxmen]

If I go to replace the bearings, how do I know in advance what size to get?

if you want to go undersize then you'll need to take the engine apart and machine the crank. if your crank has no wear (unlikely) then you can replace the bearings with stock size. Chrysler had 1 and 2 thousands undersized bearings on the assembly line and dealer parts for clearance fitting (for both upper and lower half, i doubt you'll still find any but you could ask at a dealer) - you need to check with a plastigage and see what the current clearance is then decide what you can use. download the FSM from the faq section (the engines chapter) and the procedure is explained in there. Depending of the wear on the crank (and scratches or lack of on the journals) you might be able to just use stock size or machine the crank to 10 under and use the appropriate bearings.

[dwtaylorpdx]

There is no way I'd just replace the bearings and not do the cylinders,
basically rebuild the engine.

Yea you could do a bottom side replacement but it would be fairly
unusual for the bearings to be worn and not the rest of the motor.

You might find that just jumping to a heavier  oil, 15w50 or 20w50 would do the trick,
The 2.5 engine were never clearanced for the lightweight oils the newer cars are using.
My personal belief is it was a plot to get everything before 2000 off the road.
Same with taking the zinc out of the oil...

When I got my engine done it was becasue I wanted to be a bit proactive,
its always cheaper to rebuild when nothing has broken, and I had run a weekend chasing
rally cars and ran the motor really harder than it should have been  ...
I had 168K miles at the time, the cylinders needed .030 to be true,
the crank and rods needed .010 turned on the crank, the cam was worn out.

It cost me about 2000 for a really thorough rebuild by a friend. Would have been about 3000
to have most engine shops do the same work. B&B, Head work, deflash and drill the block and surface seal, degree in the
camshaft and check all the lobes.  Hesco Cam/Lifters/Springs, Silvolite Pistons,
good engine kit, high pressure oil pump(Not High volume). A stock rebuilt production
motor is about 1800 from the auto supply places.

I don't think your in a rush, I'd just keep good oil in it and try not to rev past 5500... 

Cheers
Dave

[sharpxmen]

yeah, 15w might do the trick, 20 is too thick though.

..., high pressure oil pump(Not High volume).
...

why high pressure? 75psi is the stock relief valve cutoff, what's the one you got at?