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A friend called yesterday and asked me about this problem. Anyone have any ideas? Dodge ram truck with a 5.9. Oil pressure drops to about 5psi after it runs for 20-30min. Shut it off and start it up and it is right back to 30ish at idle, then after 20-30 min eases back down to 4-5psi. They had put a new sending unit in it and also changed the oil and filter. I told them to put a cheap oil pressure gauge on it to confirm the idiot light was working correctly and it was.It does the same thing (roughly) if it is the first start in the morning or if the engine is warmed up. They said it runs smooth and quiet.
 

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i've heard that these blocks will crack around the cam journals, and cause this, is it overheating at all?
 

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A friend called yesterday and asked me about this problem. Anyone have any ideas? Dodge ram truck with a 5.9. Oil pressure drops to about 5psi after it runs for 20-30min. Shut it off and start it up and it is right back to 30ish at idle, then after 20-30 min eases back down to 4-5psi. They had put a new sending unit in it and also changed the oil and filter. I told them to put a cheap oil pressure gauge on it to confirm the idiot light was working correctly and it was.It does the same thing (roughly) if it is the first start in the morning or if the engine is warmed up. They said it runs smooth and quiet.
I had the same thing happen to mine, did the same thing your buddy did to troubleshoot it with the same results. I even went the next step of changing the oil pump. Same results. I didn't tear down the engine or anything but I drove it like that for a couple thousand miles....I figured if there was no knocks and the lifters didn't tick it was getting oil. I soon there after replaced the truck.

Sorry, not much help.
 

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Discussion Starter #4
i've heard that these blocks will crack around the cam journals, and cause this, is it overheating at all?
They said it was at about 190*
 

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A friend called yesterday and asked me about this problem. Anyone have any ideas? Dodge ram truck with a 5.9. Oil pressure drops to about 5psi after it runs for 20-30min. Shut it off and start it up and it is right back to 30ish at idle, then after 20-30 min eases back down to 4-5psi. They had put a new sending unit in it and also changed the oil and filter. I told them to put a cheap oil pressure gauge on it to confirm the idiot light was working correctly and it was.It does the same thing (roughly) if it is the first start in the morning or if the engine is warmed up. They said it runs smooth and quiet.
Sounds like shit in the pan getting sucked up to the pick-up and when you shut it off it settles back to the bottom.
 

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one guy at school has a similiar probem. the 350 in his dodge holds 40lbs at cold idle, 40 at driving speed hot but will go to 0 at hot idle
 

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I had a 318 in a dodge van. it would start at 30 psi and in a matter of 10 minutes it would have less then 5. I would pull into the track and the tech guy would see the oil pressure gauge and say "hey man you have no oil pressure", I'd comment that I had no oil pressure for the last hour. I tried a new pump, but ultimatley it was excessive bearing clearences, and there is no band aide fix for that.
 

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i'm agreeing with the crap in the bottom of the pan idea, seen that a whole bunch of times. and i will add that when you check oil pressure on one of these, don't go by the gauge on the dash. it isn't a true gauge, especially in reference to the numbers on it. always check oil pressure with a known good mechanical gauge, unless you have a drb II, then you can use pep tools and all that fancy crap.
 

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if you pull the pan--and there's not that much "crap" in there--clean it out and try it--BUT i have ran into this several times in the past---its the cam bearing's---worn out just enough --when the oil heats up--gets thin and cant fill the gap--there goes the pressure------it does take about 10-20 minutes---somestimes sooner for this to happen
 

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Had a Durango R/T with the 5.9 and had oil pressure problems too (zero at idle). Pulled the covers off because of noise and could not believe the build-up on the valvetrain and underside of the covers. Kept the oil changed every 3-4K with Castrol. Put the covers back on, changed the oil / filter, and then the pressure was fine. Drove it for a couple of weeks with no more problems, but traded it at the dealer soon after. It was a real POS since the day my wife brought it home. Brakes and tranny were continuous problems as well. Hope your luck is better than ours.
 

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Discussion Starter #14
thanks for all the replies. I'm thinking it might be crap in the pan also. My thoughts on the hot oil/bearings is that if you shut the engine off after the pressure drops, then wait about 30sec to fire it up, the pressure is good for another 20-30min. Seems the oil would still be hot/thin. Is that right? Sounds like the crap settles out of the pick up and gets sucked back up. And yes, the first thing I told them was to put a mech. gauge on it and see if its the eng or wiring. Still did the same thing.
 

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I called the guy and told him what you all have said. He says thanks. I told him to pull a valve cover if its easy and see if its got build up there. I'll let everyone know when they figure it out.
 

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I have seen the exact same in three of these trucks. I had one that did it also. I would have pressure then none, drove it like that forever until one day it started tapping on way back from track loaded down. I took the pan off, cleaned all the shit out of the screen, cut the excess metal around the screen away. Then wal-lah. Pull the pan, on the 3wd's its very easy to do
 

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i have worked for dodge for over 10 years seen alot of these sludge up. junk in the pan. you would be suprised that the spec for oil pressure is 7 psi engine hot in park.
have swung alot of 5.2 / 5.9 in the past. the problem is they run them hot to clean up the emissions if you dont stay up on the oil changes they sludge up. had a 5.2 in a short bed truck sold it with 185,000 and the guys is still driving it. gotta love that valvoline .
 
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