low oil pressure

trouble1 · Mar 2, 2004

Ive done several searches on this...but couldn't come up with a answer...I had to toss a junkyard motor in my junk(88 4.0 XJ)...compression is good(120 each cylinder), runs pretty strong, no idea of the milage etc...
Ive drained the oil three times, no water...drained the antifreeze, no oil...
It starts cold and runs up to 40 + lbs..but then drops to 20 pretty rapidly when cruising...at idle, 5-10 lbs, back up to around twenty when you give it the gas.
I never cared for oil treatments, but i tried rislone, it did nothing.
I'm running 5W-30 castrol and a fram oil filter.
thanks for any ideas...this truck has got to be on the interstate thursday morning
dave

RichP · Mar 2, 2004

First, I don't think ANYBODY here is fan of Fram filters. I would first do a Mopar or Purolator filter. Then I would try running 20W50 and see if that improves the oil pressure any. It should help short term. The other thing is that jeep senders are not the best senders out there. The only way to see if your oil pressure is actually that low is to put a mechanical gauge on there and see if the sender is lying to you. Last resorts are to replace the oil pump and/or the mains. Good luck.

ChiXJeff · Mar 2, 2004

From the 94 FSM....

At idle (600 RPM): 13psi
At 1600 RPM and higher: 37-75psi

XJ gauges are known to not be the most accurate gauges and sensors in the world. I think I'd start with a replacement sensor. Or possibly running a load of 10W30.

If that's not it......I'd suspect worn bearings and/or a worn oil pump.

trouble1 · Mar 2, 2004

sorry...meant to put in earlier I installed a sunpro mechanical gauge set...hoping that was the problem...didn't work. Is 20W-50 or 10W-50 better?

Also had no clue about the fram oil filters...I shall rectify this tommorrow...dont need bad karma on the jeep

jeepguy97 · Mar 2, 2004

If all else fails and it is the bearings, run HD30 it will hold press so u can drive it but if it is the pump you should replace it, you don't need another blown engine.

Eagle · Mar 2, 2004

If there's an Advance Auto near you, get a Purolator filter.

Castrol has a 20W50 grade in conventional oil. Try that. I'd suggest trying Mobil-1 15W50 but if you're unsure of the mileage you're also unsure of the condition of the rear main seal, so switching to synthetic might not be in the cards. However, if you eventually drop the pan to do an oil pump, you can do the rear seal at the same time and then switch.

I think the 20W50 Castrol with a good filter will put you back in the game.

trouble1 · Mar 2, 2004

Eagle said:
If there's an Advance Auto near you, get a Purolator filter.

Castrol has a 20W50 grade in conventional oil. Try that. I'd suggest trying Mobil-1 15W50 but if you're unsure of the mileage you're also unsure of the condition of the rear main seal, so switching to synthetic might not be in the cards. However, if you eventually drop the pan to do an oil pump, you can do the rear seal at the same time and then switch.

I think the 20W50 Castrol with a good filter will put you back in the game.

thanks for all the replys and advice....bought a purolator filter, castrol 20w-50 oil. I also bought a slick 50 $15.00 stuff that I was told would help....should I use it or not???
thanks again, dave

RichP · Mar 2, 2004

Slick50=snake oil, waste of money.... might as well use STP.... If it's the mains then the only way to fix it is to put new bearings in and just to be on the safe side new oil pump... 20W50 in organic is the better $$ choice, organic does not lend itself well to a 10W50 spread, synthetic will do it though. Depends on how much you want to spend, the straight 30W Valvoline Fleet oil in the gallon jugs maybe...

trouble1 · Mar 2, 2004

RichP said:
Slick50=snake oil, waste of money.... might as well use STP.... If it's the mains then the only way to fix it is to put new bearings in and just to be on the safe side new oil pump... 20W50 in organic is the better $$ choice, organic does not lend itself well to a 10W50 spread, synthetic will do it though. Depends on how much you want to spend, the straight 30W Valvoline Fleet oil in the gallon jugs maybe...

must say thats what I've always thought...but, looking for a "miracle" temp fix for about 500 miles...lol, I know better. If the synthetic 10w-50 is better, I will get it...more important to spend a little more now. I'll change the pump and whatever else in a week or so once I get it to NC

MudDawg · Mar 3, 2004

Add a quart of Lucas oil additive, if that don't bring the pressure up some...something is seriously wrong...I had to stick my stock worn out motor back in my truck while I was building another motor...sure helped mine out.

sintax · Mar 3, 2004

I run castrol 20w-50 in my 89 XJ with 230 k miles on it. It starts up wtih about 40 psi, and idles at about 15-20psi when warm and will run about 30-35 warm

Dont stress it at all. Drive the sucker into the ground. Get some thicker oil if you are THAT worried about it, I can get away with it here in socal, it does not get cold.

-Scott

Eagle · Mar 3, 2004

trouble1 said:
thanks for all the replys and advice....bought a purolator filter, castrol 20w-50 oil. I also bought a slick 50 $15.00 stuff that I was told would help....should I use it or not???
thanks again, dave

NO!

rngrfrd2000 · Mar 3, 2004

i seem to have the same problem. my 91 xj 4.0 starts up at about 40 psi and warm i am running 10-20 psi depending on the rpms...after the pig is good and warm it'll drop to 0 psi when i come to a stop and the idle slows under 800 rpm (its standard) so i will give it a little gas to bring the oil pressure back up but it only seems to wanna inch up to 10 psi... i am pretty sure that with 210k on it i need to replace everything ... anybody have an idea on what the flat rate is on mains and an oil pump

low oil pressure

trouble1

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