Just out of couriosity, why does the pressure come back up after I shut it off ,wait 1 min. restart and its good for about 5 min every time? Sorry about the poor spelling but thats the last thing on my mind. Im going to drain the oil and put some 40 weight in it just see if it holds pressure. If it does then it would have to be the bearings? I just want to make sure before I buy a remanufactured block. The heads only have about 20k on them. My brother knows where I can get a 318 reman. block for about $800. Is there a diffrence between earlier model blocks and 2003? And would it be more cost effective to remove the crank have it cut and new bearings and a timing chainsince the heads are newer? And would I have to remove the tranny if I just redo the crank, can I unbolt the torque converter and push it back enough to drop the flywheel with the crank? Sorry for so many questions, But these questions are for experts! I have a good mechanical background and the equipment,but I really need a experts advice for this project. I can't thank you enough alloro!.Thanks again, Dan

 

If the reman block is a 1999 or newer, you should be fine. There were too many changes after 1998 to go that far back.

 

Well hang on a minute, first you said "After letting it cool down the pressure is 60psi", now you're saying it will come back after only being off for a minute. If it comes back only after the engine cooling down it's a spun bearing, but if it comes back after a one minute restart where the engine is still hot, then it could simply be a defective oil filter. Different symptoms result in different diagnostics, so accuracy is important.

When the pressure drops to zero, what noises are you hearing, if any?

 

Dan - I have a 98 1500 cargo van with a 5.2 and at 120,000 miles had the EXACT same problem you have described (to a tee). Oil pressure would show normal when cold but when warm would drop to zero. Restarting engine would sometimes reset things. I figured it was the sender because it was so dramatic- all or nothing. I ordered a new sender but before I had time to replace it the problem just stopped appearing. Since I'm an electrician I've seen intermittent electrical problems before and just assumed it was a bad connection - either at the sender or in the wiring. Anyways, about 2 months later of daily driving the pressure drop reappeared but this time not intermittently and restarting the engine when warm would only bring the gauge up for about 10 seconds or so. I did notice that at high revs the gauge would go back to normal for awhile as well but mostly it stayed at zero.
Well stupid me, I thought it was still electrical and drove it for a week with zero oil pressure til I could get the time to replace the sender. Well I stopped driving it when I heard the first signs of knocking. By then the damage must have been done. I replaced the sender and of course (as you found), that wasn't the problem. Next I replaced the oil pump. Congratulations to you on getting the oil pan out. I was not able to despite what the service manual said about it being possible. Had the engine jacked up all the way to the cowl and still at least 2" shy. I WAS able to replace the pump however and saw the end of the drive shaft from the distributor and it looked fine. No breaks, wearing away or anything. When I first started it up and took a 3 minute test drive it seemed back to normal. The knocking was gone and gauge reading normal. But on the second test drive- you guessed it - back to knocking and zero pressure when warm.
To shorten this long sad story I have purchased a remanufactured engine and am now in the midst of swapping. The replacement engine did not come with the distributor-to-oil pump-gear driveshaft installed and I have to remove the old one from theoriginal engine. Both service manuals I own have nothing on how to do this. How were you able to get the oil pump shaft replaced on your motor? Did you drive it up from below with a punch. I attempted to do that but it only went up a few inches before it stopped and I don't want to keep banging on it for fear of damaging it. Any advice would be greatly appreciated. I'm greasy and tired. Thanks

Mark P.S. I found heavy sludge in the old engine like you had indicated. Not sure if this is a cause of the low pressure or an effect of driving with low pressure for so long.

 

Thanks Allero, Yes if I pull over and shut it offfor a minute or 2 and restart it the pressure comes back up to about 35 or 40 psi then gradually drops down to 0. The further I drive the faster it drops to 0. If I wait 10 min the pressure always comes up to at least 40 psi even with the engine hot. I'll try another filter tomorrow its new but it may have have glogged, I put 2 cans of gunk oil flush in itwhen I was told the engine was junk, but with the pump shaft broken it probablly went right to the pan and stayed there. I thoroughly cleaned the pick up tube and pan and put a new filter and 20/50 oil in. As you sugested I removed the sending unit and blew it out with air, the passage was clear and oil sprayed out of the filter baseholes around the center threaded stub. What you say makes sence, The engine ran perfectly for the first seven miles and I warmed it up before leaving, buton the way home I had to stop 5 times to get it home! The engine sounds like new,no noise at all. I haven't let itrun longer than a miniute with the pressure at 0. Also this may be unrelated but the pcv valve is rattling like crazy now feels like a bee buzzing when you hold it. Can't wait till tomorrow to try another filter! Thanks Again,Dan

 

Hey Master Mark, The oil pump drive shaft was a little difficult too remove. I used a 1/4 " long extension with electrical tape around itto keep from scoring the sleeve as allero advised. It was tight even after the gear was was dissengaged, so I sprayed WD40 down the distributer hole, keped taping on itand it finally came out. I marked the distributor slot positionaligning with a straight edge on the outside of the distributor opening with a scriber on the metal. I also marked it when the gear disengagedsince its a worm gear so you know where to start it in.You will also want to mark the distributor position on the blockand the rotor position on the distributor, since the gear on my new shaft was mounted a few degrees different, I had to turn the distributor a few degrees to match up the rotor and distributor markings. Runs great except for the oil pressure. The shaft can be installed 180 degrees off, I dont think it matters the slot was in the same position either way. Yea that pan was a nightmare even after dissconnecting the motor mounts, tranny mounts, exhaust, ect. I actually lifted the van off the jack stands and smashed inthe the electrical control box on the firewall, then had to pry the pan out, luckly the control box still works and you can install the pan gasket after the pan is wrestled back in.Please keep me posted on your progress. Allero has ben a great help with my nightmare. Talk to you later, Dan

 

Hmm, that's weird! I wonder if you had a lifter seal blow out?! That would certainly cause a drop in oil pressure and since the valve wouldn't be opening it could cause uneven vacuum, resulting in the PVC buzz. Food for thought.

 

Mark, Just wanted to let you know the new shaft drops right in, the old ones hard to get out because deposits on the shaft. I installed a meling, if you get a oem it may line up exactly.

 

Thanks for the reply. Thats funny I was using a 1/4" extension to push it up as well. I'll try again tomorrow. I didn't mark anything since I'm swapping engines but I figure I'll put #1 cylinder on the new engine at TDC and align shaft and rotor off that.

I think I may have found out what the problem is. Did you see the link at the bottom of this page under Related Threads titled "engine loses oil pressure at idle" or smomething like that? One of the responders links to a Service Bulletin from Dodge that describes an internal oil leak that causes vacuum issues. Due to what you said about the PCV valve going nuts that may be the problem your having. To replace the gasket they reference you'll have to pull the intake manifold. I've already pulled mine and the gasket seemed fully intact but that doesn't mean there wasn't a leak. Also I did notice at the last oil change I did that there was less oil in the pan than there should have been. There were no external oil leaks. I didn't notice anything funny with the PCV valve but I wasn't looking either. So maybe that is the same problem you and I both are having. Only you were smart enough not to drive your vehicle with zero oil pressure and destroy the engine like I did.

Mark

 

Thanks Allero, The engine is running very quiet, no valves tapping.This is the first time I've heard the pcv, but thebuzzingit starts only after its warmed up and I start losing oil pressure.Its not missing that I can tell,I have a idenical van except its a 2500 and they run and sound exactly the same.Can a spun bearing go from 60 psi to 0 oil pressurein less than 10 min. Im still hoping for a clogged or faulty filter! Let you know tomorrow. Thanks again, Dan