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engine problem- oil pressure (con't)

NCSUcherokee

NCSUcherokee

NAXJA Forum User
Location
North Carolina
The problem with my engine wasnt caused only by the rockers, as refered to in my post- 4.0 rocker problem

my oil pressure gauge was not working at the time the problem started, so i am not sure if this is the cause of the problem or a symtom of it, but i installed a new sending unit yesterday to verify that i had good oil pressure and the reading didnt seem quite right to me.

At startup, it read a tad under 60 and after the engine warmed up it stayed around 40 at idle, but under any throttle at all, the pressure skyrockets. At 1500 RPM the gauge passes 80 psi, and it pegs right at about 2k RPM. What could be causing this?
 
Either the relief valve in the oil filter is stuck closed or your new sending unit is a dud. My money's on the latter.
Check the oil pressure with a mechanical gauge to confirm.
 
Dr. Dyno said:
Either the relief valve in the oil filter is stuck closed or your new sending unit is a dud. My money's on the latter.
Check the oil pressure with a mechanical gauge to confirm.
Click to expand...
Ditto.

Be sure to double check the part number on the sender, to ensure that (a) you get theright one for your year, and (b) that you get the one for a gauge rather than for an idiot light.
 
I found a Sunpro 2" mechanical oil pressure gauge at Advance Auto for $12 today. I'll be hooking up the line, or maybe even improving on it, and using it as a tester to screw into the sender port and verify. You may want to do the same.

Same gauge elsewhere ran $20-$30, and a 3" pro gauge for $60 at NAPA. This'll be an inexpensive tool... :laugh:
 
I found a Sunpro 2" mechanical oil pressure gauge at Advance Auto for $12 today. I'll be hooking up the line, or maybe even improving on it, and using it as a tester to screw into the sender port and verify. You may want to do the same.
Click to expand...

i went to advance auto and got that sunpro gauge, and....


it reads exactly the same as the dash gauge :laugh2:

what do i need to be checking now? bad oil pump, clogged lines?
 
The relief valve is in the pump - maybe you need to check that out. There's no valve in an oil filter that could raise the pressure... Depending on model there may be a check valve to prevent drainback into the pan, or a bypass that allows oil past the filter should it get so clogged it can't pass oil anymore.

In order for there to be a relief in the filter you'd need 3 ports - inlet, outlet, and relief (for the excess flow). Filters only have 2, in and out.
 
There IS a bypass in the oil filter. if the filter media gets clogged or a certain pressure within the filter is exceeded, an additional port is opened inside the filter so the oil can be bypassed w/o passing thru the filter media
 
LouisianaZJ said:
There IS a bypass in the oil filter. if the filter media gets clogged or a certain pressure within the filter is exceeded, an additional port is opened inside the filter so the oil can be bypassed w/o passing thru the filter media
Click to expand...
A bypass is NOT a relief valve, if that's what you mean. The relief valve is in the pump (see the manual) so that the pressure leaving it never exceeds the spec (70 psi?). It would be impossible for the filter to take in 70psi and output 80psi. The bypass just bypasses....
 
Dr. Dyno said:
Get a new Mopar oil filter. The oil pressure relief valve in your existing oil filter may be stuck closed.
Click to expand...

Oops. I must have been :speepin: when I wrote that. Thanks for correcting me skipc. :)
Try a new oil filter and if that doesn't work, it's just possible that the oil pressure relief valve in the oil PUMP may be stuck closed.
 
I was taught that these kinds of pumps, gear types, are referred to as IMO or I Move Oil, they are the same kind of pumps that are used on submarine hydraulic systems that supply 5,000lb hydraulics to the control systems. First time I ever saw one my fist thought was 'Hey, I know these', They are capable of some pretty impressive pressures if the bypass or regulator part is not working properly. That said I have noticed differences between K&N, Mopar and Mobil-1 filters now that I have a gauge panel in my 98 vs the idiot panel it came with. The mobil-1 filter seems to have the lowest pressure, 15 idling 45 running. Will be putting on another K&N in a week or so to see if the pressure changes again.
 
ok, so i got the pan off , a new oil pump (after breaking the releif valve trying get it to move), and rear main seal ready to go in.

Still in search of the mystery noise comming from the back end of the engine, is there anything that i can check while the pan is off to rule out any problems? i already checked all of the cam lobes that are visible from the bottom- all feel un-eaten, the crank has no play in it. what else should i check before i button it up?
 
yeah, bearings might be in order since i found this when i dropped the rear main bearing cap this morining

663019_1.jpg



663019_2.jpg



im gonna check the rest of them out...
 
question for the engine gurus here,

after doing a few searches it seems that for the 4.0L engine a main bearing going bad is somthing that seldom happens. that makes me thing that somthing else went wrong to cause this to happen. am i just paranoid or should i assume that there is somthing else wrong, like the crank is hella out of round or or the journal is tapered, ect.

any input would be appreciated
 
Check the rest of the mains and rod bearings. If the wear pattern is uneven, you'll need to have the journals reground and use undersize bering inserts.
 
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