Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of September's Ride of the Month Challenge!
1 - 10 of 10 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
97 wrangler 4.0 with 78,000 miles, has great oil pressure when started but as it warms up it drops a bit. once fully warm it will drop to zero at idle and check gauges light will come on. when driving it does move back up to about 1/4 gauge but fluctuates alot and i get a slight valve train noise-knock at about 2500 rpms when really getting on the gas, like its starving for oil-only does this when at operating temp. I have changed the sender and gauge, and they are good. I get the same results when I hook a mechanical gauge in. oil is full and very clean. I am leaning towards changing the oil pump. even when warm at idle, it will come up as I rev it to higher rpm. Thanks in advance for all the input
 

·
Registered
Joined
·
579 Posts
Man, you have a very serious problem there, if I was you, I would stop riding that Jeep until you fix it !!!
You must change the Oil filter ASAP, unless you just changed it and you still see the same results. If the oil is good, new, and with the correct Weight, you MAY have a bad oil pump definitely.
Was the Jeep yours prior to this, how long did you owned it ? Sometimes, when owners don`t change the oil often, just add whats needed, old-dirty oil keeps clogging the passages of oil, that you can tell if you look inside the valve cover through the oil refiling hole, if the parts look muddy-black with sludge, you may have a seriously clogged engine, you should take it appart and overhaul it.
If you have a neglected engine, you may have bad crank-bearings already, any old mechanic can teel you if you have that by the sound of it, please run to an old pal who is an old mechanic, and ask him/her to listed to it, before you ruin it completely.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #3 ·
Oil is new and clean. I just ordered an oil pump. If I keep the RPM's above 2000, oil pressure stays up, just drops when below that. I will be changing the oil and filter when I do the pump. But oil that is in there now is clean and smells good, filter looks new as well. I just got the jeep a month ago. I'm thinking its the oil pump, so I'm starting with that.
 

·
Registered
Joined
·
392 Posts
Your engine builds oil pressure in the crank, and around the cam in the bearings. If your crank, rod, or cam bearings are worn it will cause the same issue. Thats why I rebuilt mine. I changed the pump and it did no good. So when I did pull it apart I found bad camshaft bearings. That was my issue. If it were me, I'd pull the valve cover. Start the engine and see if you're getting a good flow of oil in the rockers. If you're getting good oil flow then its just not building pressure.
 

·
Registered
Joined
·
64 Posts
Your engine builds oil pressure in the crank, and around the cam in the bearings. If your crank, rod, or cam bearings are worn it will cause the same issue. Thats why I rebuilt mine. I changed the pump and it did no good. So when I did pull it apart I found bad camshaft bearings. That was my issue. If it were me, I'd pull the valve cover. Start the engine and see if you're getting a good flow of oil in the rockers. If you're getting good oil flow then its just not building pressure.
This is somewhat true, but usually it's just a pump. I'd send him down that road first.

Not only does old dirty oil cause it to clog, but so do stop leaks and other additives.
 

·
Registered
Joined
·
392 Posts
This is somewhat true, but usually it's just a pump. I'd send him down that road first.

Not only does old dirty oil cause it to clog, but so do stop leaks and other additives.
You're right, and I wasn't telling him to rip it apart and rebuild it. I was stating that I did change my pump first and that wasn't it. I had other issues. The pump IS the best place to start because its so simple to change. However it is still easier to pull the valve cover.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #7 ·
Just don't understand why pressure stays up and solid above 2000 RPM's, but at idle drops way off. Just makes me think pump is going out. I ordered it already, bit will also pull valve cover off and check flow. What does anyone recommend for oil in this, I have been reading about a lot of people running a Diesel engine oil, less breakdown. Also hear rotella is good, idk
 

·
Registered
Joined
·
64 Posts
"Breakdown" is a mix between carbon left after burning fuel and vaporized fuel that will settle in the cylinder. When it settles, it mixes with the oil on the cylinder walls and piston rings, then drops down in your oil pan. All oils will break down the same because of this. Yes, even synthetic. I have always used Valvoline 10W-30 Conventional motor oil and have had one engine last over 350k miles before I sold it. The second is well on its way to match that. The only way to prevent breakdown is to ensure your vehicle reaches standard operating temp and stays there for a period long enough to burn off the excess oil in the combustion chamber.
 

·
Registered
Joined
·
579 Posts
I suggested the Filter, because the Filter looks new in the outside, but can be clogged inside. And that cost how much ? $5 bucks. Replace it unless you already have YOURSELF, it`s hard for me to say this, but I have seen shops that just wipe the filters with a rag and they again look like new, but they never change it !!! Change the filter first, it cost little. If you are getting oil on the rockers, that means you are getting some lubrication, but does not prove how good it is. The Pressure is the Fail Safe Test, a known good Professional Gauge on the engines oil pressure tap. If after the filter, the problem persist, take the Jeep to a Pro to have the Oil Press checked by a Pro with a known good gauge, if still low press., replace the Pump and Pray problem goes away, if persist, we all agree that you may have to Overhaul the Engine due to worn Crank and Cam shaft bearings. I hope it`s just the Pump.
 
1 - 10 of 10 Posts
Top