Hey guys, I have a 2000 Ram 1500 4x4 with the 5.2. Just bought it a week ago, has 189k. The other morning my oil pressure, which had been 3/4 guage, dropped to 0 and sat there. I pulled over and was getting ready to shut it off but never heard any lifter chatter, it seemed fine, so after about 5min. I drove it on home. It ran for a total of 45min. and I figured it was the sending unit. It took me a couple of days before I got the sending unit changed, and the guage worked fine most of the time ( 3/4 ) but it did do it again a couple of times. After I changed the sending unit yesterday, It started with good oil pressure, ( 3/4 ), but now it will slowly drop down after it's driven for 10-20 min. and end up a little ways below 40, 20-30 or so. It will go back up and then go down again. Today I changed the oil pump. The pan looked good, not full of sludge, I blew the pickup tube out with a bunch of carb. cleaner, It flowed good. Put it all back together and it still does the same thing, ( starts normal, slowly drops, goes back up ect. ) What else could it be? My Guage? I know sombody will probably say to get a manual oil press. guage and see what it reads, but I would rather take a good beating than take the sending unit out again. Thats probably the only place to check it though. If anybody has any ideas I would sure appreciate the input. Thanks!

 

Sorry for the beating but that's really the only way to be sure ... double check the gauge.

I never could understand how an oil pump could go bad ... it's the simplest of machines (basicly a couple of gears) constantly BATHED in oil ... [>:]

 

since it has so many miles on it and you may not know how it was taken care of... try doing an internal engine cleaning with MMO... substitue in 1 quart and run it for a couple of thousand miles, then swap it out and do it again. you may have internal gunk that could be getting pushed up into the sending unit which is causing you some problems. another thing to mention is the wiring harness... if it's got oil on it fromt he previous sending unit, clean it up real good and clean the connector on the sending unit.

 

Sorry to be stupid, I'm not familiar with MMO?. I did look for oil on the connector at the sending unit,It was dry.

 

MMO is Marvel Mystery Oil... been around forever. if you put it in the crankcase it'll clean the insides of your motor. over time if there is any gunk getting pushed up into the oil pressure sending unit, it'll disolve it and clear it up. Do a search on it and you'll find lots of info in this forum...

 

have you guys had better luck with MMO vs SeaFoam? just wondering

 

The service manual calls for a min. of 6psi at curb idle. @3000rpm, between 30 and 80 psi. Mine idles at 20psi and at cruise about 32. This is with hot oil. Cold the pressures stay around 40psi. Yours dropping to zero, sounds more like a bad wire, connector or gauge. Hey its my first post. Did I do OK?

 

Earthchain, sounds like you've been keeping an eye on your truck. We always appreciate all opinions offered.

My 01 idles at 30 and runs about 70 but I've a new engine with only 5000 miles on it. The only way to really tell if the problem is internal ( gunk in the oil passages ) or external ( oil sending unit, wiring, oil pressure gauge in daash ) is to again remove the oil pressure gauge and put a mechanical gauge in. I agree that removing that oil sending unit is a royal pain. After removing the air filter and whatever else you need to to get at the sending unit, try placing a piece of plywood across your engine and use a stepladder to climb onto and lay on the plywood to do the work. I did it and while getting the dang thing out was still a pain, I wasn't all sore from kneeling and laying on across the dang engine. Place a balnket under the plywood to prevent anything from snagging ont he wood.

Good luck.

 

Thanks for all the help guys! I will probably try the MMO, ( I have seen that stuff around forever, didn't know it worked so well ). I am begining to think these pressures are normal for this engine. It doesn't drop to 0 anymore, after changing the sending unit. The lowest it goes is a little below the 40 at idle or going down the highway at cruiseing speed. It will get up to 3/4 guage when I step into it and then it drops down as the RPM's do. I was comparing it to the 5.2 in our durango ( 180k ) which keeps the guage above half.

 

Mine has 91,000 miles on it. [sm=burnout.gif] You know whats scary? My 06 Charger idles at 14psi.