Zero oil pressure at hot idle, whats up?

Posted By: MoPar Jamie

Zero oil pressure at hot idle, whats up? - 02/07/11 11:51 PM

OK guys, '87 Dodge D-150 318-2v. I finally got it unstuck from the snowbank on Saturday only to discover that when its warm it has ZERO oil pressure at idle. Hit the gas and at about 2k RPM its somewhere between 20 and 25 on the mechanical gauge. And when its cold its about 25 at idle but as it warms up the pressure drops off. You can even see the clear line to the gauge is empty.

You can hear also the lifters clattering faintly but no bottom end noise.

So, what did I do to it? 187k miles BTW. Spun bearing, worn cam bearing? I havent driven it at all since I discovered this just ran it in the drive checking things.

And yes its full of oil BTW.

Posted By: JohnRR

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 12:02 AM

What weight oil ? But as the clearances between the crank and the bearings increase the oil pressure gets lower. 187k , time for a rebuild ....

Posted By: Pacnorthcuda

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 12:07 AM

You might have a sticking oil pump relief valve thats not closing all the way. I had that happen on a SB.

Posted By: MoPar Jamie

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 12:36 AM

I think the oil is 10w40. I havent changed since I got it, my buddy had it before me and I cant remember if he changed it or not. I know he changed the filter.

It hasnt been driven much, it sat for 3 or 4 years before he got it and he really didnt drive it a whole lot.

Looks like I'm going to pull the motor soon.

Posted By: RapidRobert

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 02:18 AM

I'd pull the pan (not fun but better than the whole eng) & R&R the pump. I'm a bit confused on the descrip though: It was OK (PSI) until after it sat stuck in the snowbank for a few months

Posted By: MoPar Jamie

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 03:05 AM

No it was stuck for a few days. I tried to rock it out before I let it sit. It was fine before I tried to get it out and rocked it. I may have overdone it but I didnt think I pushed it that hard.

Posted By: RapidRobert

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 03:30 AM

Yeah & there's no direct connection between revving it up hard to unstick the vehicle & now the pump reg is stuck (or some other prob causing the low/no psi) so I'd say a coincidence but the reving might have kicked some debris loose. I'd pull the pan & check the screen & if good there then the pump. EDIT I'm assuming the pan bottom did not get mashed in the melee

Posted By: bonefish

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 03:46 AM

it could just be the gauge, id try that before divein in to the motor.

Posted By: MoparforLife

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 01:07 PM

Quote:

it could just be the gauge, id try that before divein in to the motor.

Not if like he said the lifters are rattling.

Posted By: Dodgem

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 03:30 PM

I would pull the valve covers and look for a bent pushrod and kicked lifter first! Then the stuck relief on the oil pump!

Posted By: bonefish

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 06:21 PM

Quote:

Quote:

it could just be the gauge, id try that before divein in to the motor.

Not if like he said the lifters are rattling.

good point

Posted By: 5spdcuda

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 06:50 PM

Since you're getting pressure when you rev the engine it's a pretty safe bet that the pump drive is OK. Two most likely causes since this problem developed suddenly are a stuck relief valve or goo in the pick up. Either way you'll have to pull the pan. I had a high mileage 318 do this once in really cold weather. Turned out to be the relief valve in the pump. The piston in the relief valve moves back and forth in it's bore just like the pistons in the engine. Like them over time it builds up a ring ridge. Then when you rev up an engine with cold, thick oil the pressure forces the piston past the ridge and the valve stays stuck open resulting in very low or zero pressure at idle.

Posted By: Mr.Yuck

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 07:59 PM

bad cam bearings, bad rod bearings, valve seals sucking up into the pick-up, low on oil...take your pick.

Posted By: Paul_Fancsali

Re: Zero oil pressure at hot idle, whats up? - 02/08/11 10:08 PM

My 318 Dodge trk same thing was valve seals in oil pickup plugged get a high pressure spring put it in the pump after good cleaning and you are good to go my trk ran for 6 years on 25 lbs of pressure I then replaced pump with another and it had 80 cold I just gave it away after 25 years

Posted By: MoPar Jamie

Re: Zero oil pressure at hot idle, whats up? - 02/12/11 01:32 AM

Well did more checking and the last time I ran it the lifters werent clattering but the pressure was at zeron on the mechanical gauge and the line to the gauge was starting to become clear. So I figure it had just enough to keep the lifters from clattering but that was it.

Ran about 30 on fast idle cold and as it warmed up it dropped off quickly. The most I could get it up to was around 40-45 at about half throttle or maybe a little more warmed up. let the pedal go and it dropped down to zero once again.

I think I've got bigger issues as its smoking pretty good now even out the smog pump tube thats broken off, ruling out condensation. That and the frame is broke ahead of the steering box.

Posted By: RapidRobert

Re: Zero oil pressure at hot idle, whats up? - 02/12/11 01:43 AM

Quote:

the last time I ran it the lifters werent clattering but the pressure was at zeron on the mechanical gauge and the line to the gauge was starting to become clear.

If if it has zero psi the lifters would be clattering. W those clear nylon direct oil lines they can drain back & there'll be sections of air not oil but the air is actually compressed so you do have PSI if the gauge is showing PSI. I'd still pull the pan/pump. More info on the smoking, when started how long doing it, smokes all the time, what color, idling or part throttle

Posted By: MoPar Jamie

Re: Zero oil pressure at hot idle, whats up? - 02/12/11 01:52 AM

The smoke has a blue-ish tint to it but when I took the cap loose on the radiator (it wasnt warm at all) and burped the air out of it it seemed to go away.

I'm wondering if one of the heads has a hairline crack in it that opens up when it warms up. That would explain the large air bubble in the radiator, I have NOT added any coolant to it since I've got it, just checked it and it was okay level wise. It pumped out quite a bit of coolant with the cap off.