Zero Oil Pressure on a 1969 440

[bullwy]

When I drove on the freeway I noticed that the oil pressure on my 440 was suddenly dropping from 70 psi to 60, then 50 and then 25 and then to zero, this within probably 30 seconds. I was able to shut down the engine immediately. I let it sit for 10 minutes and was checking any leaks under the car. I then started it and had 60 psi. After 10 seconds it dropped again to zero and remained there, even after firing it up a second time. There was always enough oil in the pan. I have an analog oil pressure gauge on the car. The mechanic told me today, that he thinks that the main bearings of the crankshaft are broken because he checked the oil pump, which seems to deliver 50 pounds pressure when idling, but no pressure at the oil pressure pick up port at the back of the engine. There was at no time any clunking noise coming from the engine,except the infamous clicking of the (hydraulic) lifters, but not that strong. Also never any overheating. Now, how likely is it really that there is a damage on the main bearings given this symptoms? I told the mechanic first to drop the pan and check for one main bearing before he's checking anything else.

 

[silversedan]

how old is the motor? , I'd take the pump off first and inspect it. if that's ok , I think you should pull the oil pan and check the pickup, if it's an older motor, the pick up could be blocked by old valve seals etc. that made their way to the bottom of the pan.

 

[bullwy]

thanks. the pick up is not blocked, because the pump is delivering 50 pounds when idling. it just seems that the oil is not being fed back to the oil pressure pick up port. but is it really possible that due to broken main bearings and no obvious engine noise characteristic for crankshaft damages the pressure after the oil pump outlet drops to zero? this sounds pretty peculiar to me.

 

[Cranky]

Broken bearings?? Never seen that.....but have seen worn out or 'wiped' out bearings. If that was the case, you would be hearing more than just ticking sounds. It would sound like someone was beating on the bottom of the engine with a hammer. Run from this mechanic! If the bearings were "broken", you would see bits and pieces in the filter. Pull the relief/pressure spring out of the pump and see if it's broken. That can and does happen.

- - - Updated - - -

thanks. the pick up is not blocked, because the pump is delivering 50 pounds when idling. it just seems that the oil is not being fed back to the oil pressure pick up port. but is it really possible that due to broken main bearings and no obvious engine noise characteristic for crankshaft damages the pressure after the oil pump outlet drops to zero? this sounds pretty peculiar to me.

If the engine is not feeding the oil pressure pick up port, how are you getting a reading at all?

 

[bullwy]

the pressure was measured directly at the oil filter port, not at the rear oil pressure pick up port on the block. I'm sorry when I was ambigous, I meant worn out bearings (not literally "broken" bearings).

 

[badlite]

You might have a pressure valve in oil pump that is sticking. Also what kind of oil filter do you have. If it is a Fram replace it now.

 

[lewtot184]

something you might try if you think the pump is working. take out all the oil pressure gauge fittings at the back of the block, take out the distributor and intermediate shaft and spin the pump. if there's flow you'll see it plus it will flush those back passages in case some debris is messing the gauge up. of course the gauge itself may be messed up.

 

[Cranky]

the pressure was measured directly at the oil filter port, not at the rear oil pressure pick up port on the block. I'm sorry when I was ambigous, I meant worn out bearings (not literally "broken" bearings).

Never heard of that. I have nothing but big blocks in my shop and I can't find any oil filter port that an oil pressure read can be taken from. Man, I've been doing this for a long time and I would like for someone to show me I'm wrong. Is this something that the mechanic did and showed you what he was doing? Does the shop have some kind of an adapter that screws on where the filter does to check flow and PSI? Like badlite says, the valve in the pump could be sticking. It need to be checked. All oil pumps should be checked for casting flaws or flash and to make sure the relief valve and spring are ok before installing. I also check them for rotor clearance before installing one. Some years back a brand new engine came in because the pump only had .001 rotor clearance and it locked up which killed the bearings.

 

[mopar505]

something you might try if you think the pump is working. take out all the oil pressure gauge fittings at the back of the block, take out the distributor and intermediate shaft and spin the pump. if there's flow you'll see it plus it will flush those back passages in case some debris is messing the gauge up. of course the gauge itself may be messed up.

what he said, also if you truly went to zero pressure on the engine you would have been panicking to get that key to off position with all the metallic sounds coming from under the hood. been there several times. don't sound like your case??

 

[Dennis H]

Is there a difference between checking the pump and discovering a blocked pick-up? Had a similar scare-the-crap out of you circumstance. It was the blue towel that got away. Bent rod the only collateral. Got lucky.

 

[MarPar]

sounds like maybe some sort of snot in the oiling system...be it blue towel or other-wise.

check out the bearings...tell the mechanic to take off the pan and have a look for yourself. and at the same time look at the bottom of the oil pan. see if there are any metal shavings.

 

[mopar 3 B]

thanks. the pick up is not blocked, because the pump is delivering 50 pounds when idling. it just seems that the oil is not being fed back to the oil pressure pick up port. but is it really possible that due to broken main bearings and no obvious engine noise characteristic for crankshaft damages the pressure after the oil pump outlet drops to zero? this sounds pretty peculiar to me.

Just because you are not getting a reading on your analog oil pressure gauge in the car does not mean the port is not getting oil. What type of analog gauge is it ( mechanical or electric ) and have you bothered to check the gauge for proper function? How is the mechanic checking oil pressure at the pump? There are no test ports at the pump and the oil pressure spring plug is an real tight fit for placing any test equipment.

 

[Tempest 455]

You might have a pressure valve in oil pump that is sticking. Also what kind of oil filter do you have. If it is a Fram replace it now.

Ditto on the Fram. There used to be some tracks when you were tech'd would not let you run if you had a Fram.

 

[lewtot184]

the threads on the pick-up can develop cracks and cause pressure issues. i have a friend who installed a '70-'71 6-pak pan and pick-up, (pick-up was tight against the bottom of the pan), and eventually the pick-up developed a crack at the threads and lost oil pressure.

 

[bullwy]

He said he has a tool to attach to the oil filter port. I will go to the shop today and check at least one bearing. In my experience zero oil pressure and worn out bearings always means horrible engine noise (missing here) and overheating (also missing). I also will check if the oil pressure port on the back of the engine is clogged. I keep you posted

 

[Daves69]

Rotor spinning on shaft? Throw on another pump?

 

[5.7 hemi]

Oil pump shaft?

 

[Daves69]

Oil pump shaft?

Yeah, seen it on pressed gear chemical pump shafts. I'm sure the same might be possible with a gerotor pressed on a shaft.

 

[66Satellite47]

Bad filter or pressure relief valve/spring that operates erratically?

 

[dvw]

Cut the filter apart and look. Unpleate it and look. Debris in it? Bearings don't wear suddenly. Filter look ok? Pull the pump and dissemble. Very easy. Is the relief valve sticking? Pick up could be plugged. That's why after sitting it regains pressure until the volume of oil forces the debris on the screen and closes off the feed area. Detective work will save grief and $.
Doug