low oil pressure

My info shows 6 psi@1000rpms. Shows 18 psi@2000rpms. MOD shows these specs. They are probably minimum specs, so the reading could be a little higher. These databases are not always correct,but, I don't carry these specs in my head, so I have to look it up.

I am getting my oil pressure low warning on my display on my 2005 Chevy Silverado HD1500. I had it looked over by a friend, changed the oil. Seemed to go away. Now that it is getting cold, it's a daily occurrence. Once the truck warms up, It's fine, however I don't want to be running my engine with insufficient oil coverage.
What do you recommend? I have very little mechanical experience but also don't want to take it to a shop and get taken to town on my charges.
Is my oil pump shot? Any other things I can try to rule out before biting the bullet on a new oil pump?

The oil pump is the last thing to think about. First, have the oil pressure checked with a mechanical gauge to see if it really is low. If it's okay, suspect the sending unit. If the pressure is low, suspect worn bearings. The clue to worn bearings is the oil pressure will come back up when you raise engine speed a little. Typically a defective sending unit that's reading low will do it at any engine speed.

Thanks for your timely response!
I am wondering what kind of bearings you are referring to? When I do increase the RPM's (whether in neutral or in drive), the oil pressure does increase - sometimes a little, sometimes a lot - again depending on engine temp (more if warm, less if cold).
And the warning message (and constant chiming) will remain until it reaches a sufficient pressure (approx. 135 kPa/20 psi).
Thanks again for your help!

The bearings are thin curved strips of metal that sit between the crankshaft "journals" and the connecting rods, and between the engine block and crankshaft. They usually have three layers of metal. The first layer is real soft so dirt and grit embed in it rather than going around and scratching the polished surface of the crankshaft journals. The next layers are harder to absorb impact.

The gap, or "clearance" between a bearing and the metal part riding on it is very tight; in the order of .005". Oil is forced into that gap under pressure to isolate the moving parts from each other. That oil oozes out the sides, then falls back into the oil pan or gets whipped around to coat other areas, namely the cylinder walls.

The oil pressure is maintained because it's hard to push the oil through the tight clearances. Anything that makes it easier for the oil to run out will result in lower pressure. Oil gets thinner when it gets warm. That lets it run out faster, so the volume being pumped has to increase. Most oil pumps have no problem pumping enough volume, but with low pressure, those moving metal parts can start to make contact. The soft first layer of metal begins to rub off of the bearings. You can actually see that as a significantly discolored area. The missing metal results in increased clearance so the oil can run out even easier and will be less effective at isolating the moving parts. Once that wear starts, it accelerates real fast until you hear a knocking noise from the parts banging against each other.

If this is caught early enough, sometimes new bearings can be installed and the wear stops taking place. That has to be done before the journals becomes scored or scratched. Any roughness on a journal will tear up the new bearing. For a V-8 engine, the crankshaft sits on five bearings, and there's eight connecting rod bearings. It only takes one of them to be worn to allow the oil to run out too fast and cause low pressure.

Depending on the engine design, there are usually five or six camshaft bearings too. Those get oil in such a way that there's not much pressure left. They don't have to handle the same pounding forces as the other bearings so they rarely cause a problem.

Installed a new cam in the motor, after initial startup there was no oil pressure registered on the gauge. We replaced the oil pump with a brand new Melling unit. Reassembled engine and tried again, this time disabled the starting system and just cranked it. No pressure registered on the guage. Pulled valve covers to verify and there is no oil pumping up pushrods. I am stumped, has anybody got any ideas?? Do you prime the pump, if how?? Any resoponse will be appreciated.

[quote:b203d2c031="txhotrod"]Engine Mechanical problem
2005 Chevy Silverado V8 Two Wheel Drive Automatic 86000 miles
----------------------------------------------------------------
Installed a new cam in the motor, after initial startup there was no oil pressure registered on the gauge. We replaced the oil pump with a brand new Melling unit. Reassembled engine and tried again, this time disabled the starting system and just cranked it. No pressure registered on the guage. Pulled valve covers to verify and there is no oil pumping up pushrods. I am stumped, has anybody got any ideas?? Do you prime the pump, if how?? Any resoponse will be appreciated.[/quote:b203d2c031]

whats your engine size? 4.8 or a 5.3, also to make sure Im looking at the right picture is the oil pump mounted to the crankshaft

Thanks again.
So get it on a mechanical gauge, and see if oil pressure is actually low. If not, then it's likely the sending unit. If oil pressure is low, likely the bearings? Which would be a pretty costly repair, correct? Fingers crossed it's the sending unit..?
Sorry for the constant replies, as I mentioned I'm not mechanically inclined!
Thanks again. Very appreciated!

It is a 5.3 and yes the oil pump is on the front of the motor, being turned by the crankshaft.


[quote:e8cec071ef="Buzzsaw"][quote:e8cec071ef="txhotrod"]Engine Mechanical problem
2005 Chevy Silverado V8 Two Wheel Drive Automatic 86000 miles
----------------------------------------------------------------
Installed a new cam in the motor, after initial startup there was no oil pressure registered on the gauge. We replaced the oil pump with a brand new Melling unit. Reassembled engine and tried again, this time disabled the starting system and just cranked it. No pressure registered on the guage. Pulled valve covers to verify and there is no oil pumping up pushrods. I am stumped, has anybody got any ideas?? Do you prime the pump, if how?? Any resoponse will be appreciated.[/quote:e8cec071ef]

whats your engine size? 4.8 or a 5.3, also to make sure Im looking at the right picture is the oil pump mounted to the crankshaft[/quote:e8cec071ef]

Yup. You got it right. For Ford products replacing the bearings is a major job because the engine has to be lifted to get the oil pan off. For yours, and most other brands replacing bearings can often be done in half a day. Once it gets bad enough that the crankshaft is damaged, the engine has to be removed, and the job is sufficiently involved that you might as well do a total rebuild.

[quote:53e4c893e5="txhotrod"]It is a 5.3 and yes the oil pump is on the front of the motor, being turned by the crankshaft.


[quote:53e4c893e5="Buzzsaw"][quote:53e4c893e5="txhotrod"]Engine Mechanical problem
2005 Chevy Silverado V8 Two Wheel Drive Automatic 86000 miles
----------------------------------------------------------------
Installed a new cam in the motor, after initial startup there was no oil pressure registered on the gauge. We replaced the oil pump with a brand new Melling unit. Reassembled engine and tried again, this time disabled the starting system and just cranked it. No pressure registered on the guage. Pulled valve covers to verify and there is no oil pumping up pushrods. I am stumped, has anybody got any ideas?? Do you prime the pump, if how?? Any resoponse will be appreciated.[/quote:53e4c893e5]

whats your engine size? 4.8 or a 5.3, also to make sure Im looking at the right picture is the oil pump mounted to the crankshaft[/quote:53e4c893e5][/quote:53e4c893e5]

yes you do have to prime it, you fill it full of oil and then use clean fresh white lithium grease to keep it in there( cover the holes with it )

So you are saying to plug up the outlet hole by the pressure relief valve with grease, fill up the pump then do the same to the inlet and install the pump? Correct??

OKay so I was driving after a 120 mile trip about 2 miles from home and started to get some valve chatter when i got home I parked it and the next morning I fired the truck up and it said low oil pressure I checked the oil and some had scored on the stick. I am not getting ANY oil pressure. DO you think it is the pump? The Motor is a 4.8

Make sure the oil level is full. Check the oil pressure with a test gauge. If there is no pressure, replace the oil pump. If the pressure is good then goes away, check the main and rod and cam bearings. You could also check the seal on the oil pickup tube.Make sure it isn't damaged.

[quote:176104647e="txhotrod"]So you are saying to plug up the outlet hole by the pressure relief valve with grease, fill up the pump then do the same to the inlet and install the pump? Correct??[/quote:176104647e]

yes with white lithium grease in a tub then install it, before putting everything back together see if you have pressure(turn it over), make sure the crank is turning, make sure the key is in the crank for the oil pump flange that goes into the pump off the crank

It worked! Put it back together and it immediately picked up oil pressure upon starting. Thanks!

The low oil pressure indicator comes on but I check the oil and it's fine do you know what the problem could be on a 2004 chevy silverado?

Check the oil pressure with a mechanical gauge,if normal replace the oil pressure switch. If abnormal could mean oil pump and/or engine bearing.

04 silverado ss 6.0L did a oil change Mobil 1 and filter. Week later started up and no oil pressure a little gas and it went up. Two days later nothing. Put new sending unit in and nothing. Put a mechanical gauge and still nothing. Pulled sending unit out and cut off fuel so don't kill motor and no oil came out of where sending unit sits.

Could it be oil pick up, Or maybe the oil pump?
Or somthing else??

Could be the pick-up or the pump itself

it might be the pressure relief valvestuck in the oil pumpp. the pump is under the timing cover. there is an older TSB telling of oil filter misapplication and causing damage. You might try a new AC filter to see if that cures it.

2002 Chevy silverado 1500 4.3 V6 When I start my truck the oil pressure goes to 40 but when I stop at a light or stop sign the pressure goes down to 20 what would cause this and how would I fix it. RE. we switched to synthetic oil last oil change and used motor flush before we changed the oil.

[quote:d2b3d38519="jeffrohotrod"]2002 Chevy silverado 1500 4.3 V6 When I start my truck the oil pressure goes to 40 but when I stop at a light or stop sign the pressure goes down to 20 what would cause this and how would I fix it.[/quote:d2b3d38519]

The oil pump moves with increase RPM's maybe it needs crankcase cleaning/engine flush to clear a partial clogged screen/oil galleries and/or out of calibration oil sending unit.

Low Oil Pressure after truck gets hot.

This may not be serious.....or it could be!

If you are experiencing funny noises or knocking at low pressure for sure, it is probably serious!

Have you checked your oil level? Surely you have!

(now, a little bit of preaching!)

What i mean is "you"---not "dave" down at the "super dooper lube" two months ago!!! (this is how some people check their oil!)

It is important to check it at minimum, "weekly" as probably prescribed in your owners manual....and also if you suspect a problem or your gauge or light says you have a problem! Anything could happen within seconds, your oil plug falls out (installed wrong) or road debris knocks a hole in your pan!.....if oil is the issue, immediately shut it down!!!....no limping it another 500 feet!

Even if you "have oil"---your oil pump may not be working!

Have you kept up with scheduled changes?

Using the correct oil?

(preaching is over!)

Remove your oil pressure sender and install a mechanical oil pressure gauge---this will give you a real accurate reading as to what your actual oil pressure is, and is doing while being driven.

A gauge set up sorta like mine, or an aftermarket under the dash mount (used as a portable, temporary test platform) will allow it to be run out from under the hood and into your window, so you can watch it as you drive, on top of the dash, or in the seat beside you.....might pick out a pertty one, you may want to mount it permanently and do away with the electric one!

If it says everything is a-okay with the mechanical gauge

Then most likely your sender is defective (normally the problem in cases like yours)--- the actual gauge in the dash would be the second guess as to being bad, or the wiring in between

Some people just change the sender as their "test", that is fine, unless it does not seem to work out

I, myself, like to know what the "real deal is", before i buy a part....i can't afford a new engine either.......parts changing is kinda a weigh it out thing $$$/ time/ satisfaction with results.....or you now have a working old spare part!

I was told that 4 psi was adequate pressure to lube an engine, by a local production engine re-builder (i would not want that myself!) The norm in my '77 cj 5 is between 40-60 psi.....20 psi is when i start getting alert and ready to rebuild!

A "high volume" oil pump is available for my engine (may be able to find one for yours too) i have installed several on this and others i have owned previously. They have increased my pressure, and cost about $120 or so, just a guess, i gained maybe another 60,000 miles, before pressure dropped off again.

This may be an option for you, if the mechanical gauge does prove that you do have wear and tear, and pressure just ain't gonna improve until you do something mechanical. High volume pump/ internal bearings/ or a rebuild

See my pic below of my gauge

Be sure you keep us posted.

The medic

My oil pressure is running low around 30, I've change the oil and filter,
and still the same. I got an oil leak I can't seem to find, its seem to be getting worst. It's all over the
bottom of the engine area.
LB

if it's 30 psi at idle it's not bad. Its best to manually check the oil pressure with a gaugea s the electric ones can be off. Also it depends on the oil filter you are using if you feel it's low because of that. the following is considered normal oil pressure hot......
Oil Pressure (Minimum-Hot)
41 kPa at 1, 000 engine RPM
124 kPa at 2, 000 engine RPM
165 kPa at 4, 000 engine RPM6 psig at 1, 000 engine RPM
18 psig at 2, 000 engine RPM
24 psig at 4, 000 engine RPM
see pics on where to check for leaks. amek sure to wash off all oil so you can find the leak to begin with or you never will

I recently had my intake manifold gasket replaced to stop a coolant leak. Before this was done, my oil pressure was good. Since then the oil pressure goes down to around 5-6 PSI at hot idle especially when I put some strain on the power steering. Revving the engine slightly gets the pressure to go up. When I first start the engine, the pressure is around 25 PSI and there is a slight tapping noise which goes away in about a minute. As the engine heats up, the oil pressure drops and the operating PSI is about 10 -15.
I am considering replacing the oil pump and screen. Would this help? I am currently running 5W-40 high mileage oil.

put a manual gauge on it first see if it does the same it may be wear on bearings or a bad oil filter if that was replaced.

My dad owns a 2001 Chevy 3/4 ton with the 6L v8; it is a work truck. Just recently my dad tried to start it and he noticed that the trucks oil pressure gauge was at zero he immediatly shut the truck off. Now the truck at the time was running smoothly and when the oil pressure gauge stayed at zero the engine didnt make any funny noises and ran perfectly normal for the few seconds the engine was running.

So would it be the oil pump? or a faulty gauge?

Hello - Based off the information given you have a bad oil sensor. The IPC uses the engine oil sensor signal to determine the engine oil pressure. The oil pressure sensor signal circuit is hard-wired to the IPC. The engine oil pressure sensor signal to the IPC is a variable resistance ranging from 0-90 Ohms . A sensor resistance of 1 Ohms will display as 0 psi (0 kPa) and a resistance of 88 Ohms will display as 80 psi (550 kPa) . The Check Engine Oil Pressure indicator will be displayed in the message center if the IPC detects a low engine oil pressure.

Tools Required: J 41712 Oil Pressure Sensor Socket Remove the engine sight shield. IMPORTANT: Clean the area around the sensor before removal. Do not allow debris to enter the engine. Disconnect the oil pressure sensor electrical connector. Remove the oil pressure sensor using the J 41712 or equivalent. INSTALLATION PROCEDURE Apply sealant GM P/N 12346004 or equivalent to the threads of the oil pressure sensor. NOTE: Refer to Fastener Notice in Service Precautions. Use the J 41712 or equivalent in order to install the oil pressure sensor. Tighten Tighten the oil pressure sensor to 20 N.m (15 lb ft) . Connect the oil pressure sensor electrical connector. Install the engine sight shield. Check and adjust engine oil level.

wow thanks for the info! this has got to be the most helpful site on the net!

ps thanks again!!!!

My truck lost oil pressure so I decided to drop the pan and change the oil filter, clean the pan, clean the tube ,the screen, even replace the oil pump. put it all back together and I still have no oil pressure. I know it's not all them because I can hear a little bit of ticking. so I cut my truck back off I prime the pump from the bolt hole on the engine block on the left side with the hex head bolt hole it gets old pressure for a few seconds and pulls slowly back to nothing. I tried that twice it's like it's not picking up the oil from the pan. do I need to keep priming? I don't know what to do.

Good morning and thanks for visiting,

Generally when you prime an oil pump you don't have to do it for long, and you don't have to do it again. Do you have a way to put a mechanical gauge and measure the oil pressure that way?

We basically need to find out whether or not you have actual oil pressure loss here or if its something electrical.

Hearing "a little bit of ticking" is normal really.. Since you said that, i'm inclined to think that its electrical. Because no oil pressure usually makes lots of clanking noises.

Until you can verify whether there is (or isn't) any oil pressure don't run the engine too much or rev it up. just until you find out.

Hope that helps.
Jon

The oil pressure gauge in my truck works because when I prime the pump from the front of the block with the hex bed head bolt it shows oil pressure good for a few seconds and then slowly falls back down to nothing. I don't have a manual oil pressure gauge.

Okay, fair enough!

In that case, can you tell me about when you had the pan off, what sort stuff did you find? In the bottom of the pan, in the pickup screen, pickup tube. Etc. any debris or gunk?

Regards
Jon