No oil pressure at idle

[Redtide]

I've got a 2003 4.7 ram 1500. I recently did a coolant change since the previous owner put in the wrong coolant, and as I was attempting to bleed the system my oil pressure gauge would go to zero at idle once it was warmed up. I mentioned the coolant change since I feel like that might have something to do with the issue since I've never had anything but normal pressure until then. I've already done the obvious thing of switching the oil pressure sensor, and I noticed that I was just under a quart low on oil from various leaks, and a missing PCV valve that I just fixed. I topped off the oil hoping that was the issue but sadly it was not.

Right now, I'm planning on getting a mechanical gauge to ensure that I really am losing oil pressure (the truck runs funny after driving from a stop, and that goes away once the pressure comes back, so I'm prettttty sure the readings correct). I'm then going to remove the oil pan, and make sure the pickup tube isn't clogged, and replace the oil pan gasket at the same time to stop that leak. This is unless its bearing failure, dunno what I'll do then. Just looking for some advice, maybe someone's had this issue and its a problem I'm not aware of.

The only code I have one the truck is a PO499 "Evap Emission system vent valve control ciruit high" code. Just on the odd chance that that's related which i doubt it is. TIA

 

[Smokeybear01]

Does the pressure return to normal while you're driving or is it still lower than previously, but close to normal? That will indicate a bearing going out.

 

[Redtide]

The pressure comes right back to the normal range right about say 1500 rpm, goes straight to zero the second it idles. It being lower than normal permanently is what signifies bearing failure?

 

[crash68]

The pressure comes right back to the normal range right about say 1500 rpm, goes straight to zero the second it idles.

Verify pressure with an analog gauge but guessing the pressure transducer is probably going bad.

 

[Redtide]

Verify pressure with an analog gauge but guessing the pressure transducer is probably going bad.

I'm checking with a mechanical gauge right now. I'm new to mechanics, this is my first vehicle, and I have no idea what a pressure transducer is lmao

 

[jws123]

I'm checking with a mechanical gauge right now. I'm new to mechanics, this is my first vehicle, and I have no idea what a pressure transducer is lmao

How many miles on it ?. I have had many 4.7s with this issue its 1 of 4 things. 1.oil sender failed .2 You dont do regular oil changes every 3k like a 4.7 needs so it sludged up. 3. I fits high miles over 200k or near it main bearings are wore out. 4. Oil pump sometimes fixes this issue but not always if main bearings are wore.

 

[Redtide]

How many miles on it ?. I have had many 4.7s with this issue its 1 of 4 things. 1.oil sender failed .2 You dont do regular oil changes every 3k like a 4.7 needs so it sludged up. 3. I fits high miles over 200k or near it main bearings are wore out. 4. Oil pump sometimes fixes this issue but not always if main bearings are wore.

Its got 135k miles, altho i got it around a year ago at 130k miles. I don't drive it that much because its had various simple issues. Previous owner used it to tow his boat and id assume go off roading since he had it on 37s. Had bad maintenance, leaks everywhere, but I got it cheap so I took the chance. He told me he changed the oil right before selling, but there's no way cuz it was pretty dirty, I'm right at its next oil change now.

Just did the mechanical gauge check, started out at 30-35 psi, then once then immediately started declining psi pretty consistently. I let it run, and it went to about 9 psi before she started the typical rough idle and i shut her off. This is before the check oil light even came on so I'd assume she gets lower once fully warmed up. Also like an idiot, I assumed that I had a failing power steering pump, but I know realize that sound is prolly a lifter getting smacked around. It almost sounds like loose metal bouncing around so thats great.

 

[Redtide]

As I mentioned I already replaced the Oil Pressure Sensor, I've had the valve covers off because of leaks and it didn't seem sludged up more than usual. I'm just trying to figure out it its bearing failure or an oil pump. If its bearing failure I'm going to swap the engine. If its an oil pump, would I be safe to replace the pump, and all the lifters? I'd assume there's metal grit from the lifters getting smacked around.

 

[jws123]

As I mentioned I already replaced the Oil Pressure Sensor, I've had the valve covers off because of leaks and it didn't seem sludged up more than usual. I'm just trying to figure out it its bearing failure or an oil pump. If its bearing failure I'm going to swap the engine. If its an oil pump, would I be safe to replace the pump, and all the lifters? I'd assume there's metal grit from the lifters getting smacked around.

Its hit or miss sometimes a oil pump fixes it sometimes it doesnt. To swap oil pump you need to pull timing cover remove timing chains drop oil pan down Not out just down and remove the pickup tube. It may be easier to pull engine check bottom end or just swap the whole thing its up to you. Personally I would throw bearings in it, replace timing chains,replace oil pump,change valve stem seals a must!!. All of those are common fail points once you do that its bulletproof.

 

[crash68]

I have no idea what a pressure transducer

It's a more technically correct description of an oil pressure sensor.
A transducer coverts mechanical energy into an electrical signal.

 

[Redtide]

Its hit or miss sometimes a oil pump fixes it sometimes it doesnt. To swap oil pump you need to pull timing cover remove timing chains drop oil pan down Not out just down and remove the pickup tube. It may be easier to pull engine check bottom end or just swap the whole thing its up to you. Personally I would throw bearings in it, replace timing chains,replace oil pump,change valve stem seals a must!!. All of those are common fail points once you do that its bulletproof.

Thanks for the info. If I have to pull the engine, I'm probably just going to replace it with a 5.7. From what I understand I have a 545RFE trans so I should be able to drop in a 5.7 and replace the ecu and wiring harness. Is that something thats not possible? Basically I could go through with the work to replace the oil pump, and it might be for nothing because I have bearing failure? There's no other way to tell the difference between the 2?

 

[Redtide]

It's a more technically correct description of an oil pressure sensor.
A transducer coverts mechanical energy into an electrical signal.

Got it. I already replaced that component.

 

[jws123]

Thanks for the info. If I have to pull the engine, I'm probably just going to replace it with a 5.7. From what I understand I have a 545RFE trans so I should be able to drop in a 5.7 and replace the ecu and wiring harness. Is that something thats not possible? Basically I could go through with the work to replace the oil pump, and it might be for nothing because I have bearing failure? There's no other way to tell the difference between the 2?

Not worth swapping to a 5.7 many have tried cheaper to get another truck. The 4.7 is a good engine just sounds like yours was beat on and no not really a way to tell if its the pump or bearings without looking at bearings ect ect.

 

[Redtide]

Not worth swapping to a 5.7 many have tried cheaper to get another truck. The 4.7 is a good engine just sounds like yours was beat on and no not really a way to tell if its the pump or bearings without looking at bearings ect ect.

Gotit. Thanks for the help and information

 

[Smokeybear01]

As I mentioned I already replaced the Oil Pressure Sensor, I've had the valve covers off because of leaks and it didn't seem sludged up more than usual. I'm just trying to figure out it its bearing failure or an oil pump. If its bearing failure I'm going to swap the engine. If its an oil pump, would I be safe to replace the pump, and all the lifters? I'd assume there's metal grit from the lifters getting smacked around.

If it sounds like a knocking, it's definitely bearings going.

 

[jws123]

If it sounds like a knocking, it's definitely bearings going.

while that is correct the top end loses oil pressure first so it taps.

 

[Dodge 1500 4X4]

Dropping oil pressure like that excessive bearing wear probably your problem, for now I would try putting a thicker grade of oil you may get some more life out of it, in the past if used a straight grade of oil, like 30w.

 

[Redtide]

I think at this point I'm going to buy a parts truck with a 5.7 in it, this way I can do a swap and have all the needed parts. Should be cost affective as well from the one I'm looking at, it has right around 100k miles and he's asking 3k for the truck since its got a blown trans.

 

[jws123]

I think at this point I'm going to buy a parts truck with a 5.7 in it, this way I can do a swap and have all the needed parts. Should be cost affective as well from the one I'm looking at, it has right around 100k miles and he's asking 3k for the truck since its got a blown trans.

your better off putting a trans in that one you have to make new motor mounts ect its just not worth it also 3k is to much unless that things spotless ahaha can get em here for 800 buks

 

[Redtide]

your better off putting a trans in that one you have to make new motor mounts ect its just not worth it also 3k is to much unless that things spotless ahaha can get em here for 800 buks

I have thought of that LOL. I don't think I could do that though, I've done so much to this truck already, my last project was rebuilding my rear diff which wasn't fun (Its been 500 miles since that), so I'd rather spend more to keep it honestly. I was planning on doing a tear down on the 5.7 and putting new seals and addressing any issues it might have. If I get the parts truck I just take its motor mounts and switch them to mine, same with brake lines and ac lines, pcm, harness and all the other parts. If I were to get a 5.7 parts truck, where would yall look and what would you offer?