• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Oil Pressure issue at idle

R

robertmee

Full Member
Joined
Jan 25, 2018
Messages
133
Location
Raleigh, NC
My 2003 Avalanche that is now my teen sons transportation. He's a want to be mechanic and we're doing an engine swap on his Eclipse, so he is familiar with Engines. Today, on a 5 mile ride to school, about a mile away, the low oil pressure message came on at a Yield and Pressure showed 0. He went to pull over to a safe spot, and the pressure went back up to 40 while driving. He continued the final mile to school and when stopping to pull into school, the message came on again, and the pressure dropped to 0. He parked and called me.

I was out of town, but had him crank the engine with hood up. Could hear an audible tick/knock, so immediately had him shut off. Truck sits now in school lot. Oil level is fine.

What should be the next step. I'll have it towed home. I assume a mechanical test kit to see if I've really lost pressure? If the oil sending unit/screen are dirty that would just cause a false reading, not actual engine failure, correct? I've read that low pressure at idle could be a bad oring on the pickup? And that having pressure at RPM but not idle would not be the pump?

I'm guessing maybe first change oil and filter and try a mech gauge? But the tick sound i heard over the phone is concerning. Hoping I'm not shopping for a reman.

Please offer advice on possible next steps or of the engine is fubar. Engine has 260k.
 
Last edited:
To clarify....the "low oil pressure " verbiage came up on the dash, not the light, and the truck did the audible ding ding. Reviewing with my son again, it was less than a minute, maybe 15 seconds, that it came on twice. Once when stopping briefly at a yield, and the second time when pulling into the parking lot.
 
what did oil pressure gage show?
 
To clarify, the 2003 Avalanche does not have the little filter screen under the oil pressure sensor.

That device came into play with the 2007 and upwards AFM engines.

No need to go looking for that screen.

The easiest and cheapest thing to try first would be to install a new ACDelco oil pressure sensor.

Given the age and probable mileage of the truck, it would not be unheard of for parts to be getting old and worn out.

If the new pressure sensor shows the dash gauge to be reading accurate, then the problem will begin to get a little more involved and more expensive.

On my 2004 EXT, I chased some oil pressure issues a while back.

I first changed out the oil pressure sensor to no avail.

Next, I paid to have a new oil pick up tube o-ring installed.

That seemed to help for a short period of time, maybe a month.

Finally, I had a new Melling high volume oil pump installed.

Now, the oil pressure is better at all RPM ranges and oil temps than it has ever been since I first bought the truck.

The truck currently has other issues, but low oil pressure is not one of them.

A common symptom of a worn out oil pick up tube o-ring is a very low oil pressure at engine idle, but the oil pressure may approach normal readings as the engine RPMs rise.

On my 2003 Avalanche, the oil pressures showed normal across all ranges and oil temps until they didn't.

The faulty oil pressure sensor caused the gauge to peg out at 80 PSI, even with the key on and engine off.

Swapping in a new pressure sensor completely fixed that problem.
 
EXT4ME said:
To clarify, the 2003 Avalanche does not have the little filter screen under the oil pressure sensor.

That device came into play with the 2007 and upwards AFM engines.

No need to go looking for that screen.

The easiest and cheapest thing to try first would be to install a new ACDelco oil pressure sensor.

Given the age and probable mileage of the truck, it would not be unheard of for parts to be getting old and worn out.

If the new pressure sensor shows the dash gauge to be reading accurate, then the problem will begin to get a little more involved and more expensive.

On my 2004 EXT, I chased some oil pressure issues a while back.

I first changed out the oil pressure sensor to no avail.

Next, I paid to have a new oil pick up tube o-ring installed.

That seemed to help for a short period of time, maybe a month.

Finally, I had a new Melling high volume oil pump installed.

Now, the oil pressure is better at all RPM ranges and oil temps than it has ever been since I first bought the truck.

The truck currently has other issues, but low oil pressure is not one of them.

A common symptom of a worn out oil pick up tube o-ring is a very low oil pressure at engine idle, but the oil pressure may approach normal readings as the engine RPMs rise.

On my 2003 Avalanche, the oil pressures showed normal across all ranges and oil temps until they didn't.

The faulty oil pressure sensor caused the gauge to peg out at 80 PSI, even with the key on and engine off.

Swapping in a new pressure sensor completely fixed that problem.
Click to expand...
Thanks for the detailed info....I believe it was one of your posts I found when searching that led me to the oring issue. And thanks for the clarification on the screen. Just so I'm clear, the oil sender failing would only effect the gauge, correct. It doesn't effect the actual oil flow...thats just from the mechanical pump, pickup, and filter (possible dirty or plug). So changing the oil pressure sensor would just confirm whether i really have low flow or not, but wouldn't cause low flow itself.
 
Correct in that the sensor is simply reporting the pressure it is reading.

An abnormally low reading, whether from a good or bad sensor, is reported to the computer which can in turn generate dash messages and low pressure readings in the cluster gauge.

If I were to bet a dollar on your issue, I would put my money on a worn out o-ring.

Quite common, especially on the older engines.

Not an overly serious problem, if addressed promptly.

I just mentioned my oil pump solution on the EXT because in my case, the o-ring was not my final solution and I had to dig a little deeper to finally solve the problem.

Is your truck 2WD or 4WD?

Edit: I see yours is 4WD.

Swapping out the o-ring on a 2WD truck is a bit easier than on a 4WD truck.

Same for the oil pump, but that job is more involved all around.

Still doable for the mechanically inclined.
 
Last edited:
Yeah, its not easy like my old Dakota. I could swap the pump and pickup in a couple of hours...just drop the pan. Looks like for the 5.3 I have to take the clutch fan out, the front timing cover and accessories and the pan. Is it just a real estate issue with the 4wd, or additional things I have to remove. I have the FSM for the truck, so hopefully it shows in detail how to change it.
 
I think I see what you mean on the 4wd. Looks like to drop the pan you have to disassemble most of the front drive train...drive shaft, axles, transfer case, cross member. What a pain. I see some other videos tho that reference doing it without dropping the pan, so maybe thats a possibility.
 
When my mechanic replaced my oil pump, in addition to removing parts from the front of the engine to access the timing chain cover, he had to remove the bolts for the front diff and then move and secure the front diff far enough forward to clear the front of the oil pan for it's removal.

The front diff also had to be moved to remove the oil pan to just replace the o-ring.

The front diff was never fully removed from the truck.

The CV-axles remained connected and the assembly was strapped
forward, away from the front of the oil pan.

It doesn't take much room to make enough clearance.

In both cases, the crossmember is just unbolted and removed for oil pan removal.

Nothing on the front of the engine will need to be removed to just replace the o-ring.

Obviously, a 2WD truck doesn't have a front diff and the mechanic doesn't have to worry about dealing with that.
 
The front drive shaft will need to be removed.

No big deal.

The transfer case does not have to be removed, at all.
 
I have seen it mentioned that some claim to have replaced the o-ring without removing the oil pan.

While this may be possible, I have trouble seeing how.

The oil pick up tube is securely bolted to the windage tray and it is not movable.

That makes me think the oil pump itself would have to be unbolted and moved to allow access to the o-ring.

Both the oil pump and the pick up tube are mounted solidly and are not going to move in relation to each other.

I would just plan on removing the oil pan to gain easier access to the tube and o-ring.

Once the oil pan is removed, the pick up tube with the o-ring can easily be removed and replaced.

If I had to, for any reason, access the actual oil pump to move anything around to access the o-ring, I'm going to replace the old oil pump just because it is old and I am right there.
 
Thanks for all the info. Very helpful. I guess the last thing to determine is what if any engine damage was done...hopefully the ticking is just some dry lifter noise.
 
If you can find and read the story of my EXT and it's issue with coolant getting into the crankcase, the lifter tapping I had with that engine was very severe at it's worst.

The coolant contaminated engine oil could not keep the lifters pumped up over night and at first start up, even with great oil pressure, the lifters were collapsed from the oil that had bled out and they would tap like crazy.

Once my good oil pump pumped enough fluid into the lifters, they became quiet again.

Even with the thin, coolant contaminated oil.

One of the strangest symptoms I was dealing with was immediately after a fresh oil change, there was no lifter tapping, at all.

It took around 500 miles for the coolant to drain enough down into the crankcase to thin the oil out enough for the lifters to collapse overnight.

While you were driving around normally, the lifters were pumped up with the contaminated oil and the engine ran perfectly quietly.

Right now, with a fresh oil change, you can go out and start the engine and it is quiet from the jump.

Since you guys did not drive the truck very much after you discovered the oil pressure problem, I would also bet that once you make your o-ring repair, you will have a good running engine and a story to tell for a long time.
 
I'm having the same issue and I did the o ring on the pick up tube last year, and did the oil pressure sensor last November but it was a duralast from autozone you think getting a AC delco will fix the code?
 
EXT4ME said:
I have seen it mentioned that some claim to have replaced the o-ring without removing the oil pan.

While this may be possible, I have trouble seeing how.

The oil pick up tube is securely bolted to the windage tray and it is not movable.

That makes me think the oil pump itself would have to be unbolted and moved to allow access to the o-ring.

Both the oil pump and the pick up tube are mounted solidly and are not going to move in relation to each other.

I would just plan on removing the oil pan to gain easier access to the tube and o-ring.

Once the oil pan is removed, the pick up tube with the o-ring can easily be removed and replaced.

If I had to, for any reason, access the actual oil pump to move anything around to access the o-ring, I'm going to replace the old oil pump just because it is old and I am right there.
Click to expand...

I watched a few videos. It's a pain, but doable. You don't need to move the pickup tube so it can stay bolted to the windage tray inside the pan. You remove the bolt between the pump and pickup, which is the hard part. It's recessed an inch into the pan, but accessible with a skinny wrench and a magnet to hold it so it doesn't drop into the pan. Some use mechanic's wire to wrap the bolt and hold it also. You can also take the face of the pump off and remove the pump gears and that gives more play and room to remove the bolt. Once the bolt is out, you can remove the pump with a little twisting effort, then replace the o-ring on the tube that's now exposed. I think it's more of a pain because most are laying on their back trying to get it. I'll have mine on my lift and at eye level so I'll probably give it a whirl. Worst case I drop the bolt into the pan and have to take the pan off anyway.

In regards to the O-ring, do you know if the 2003 has the tapered or straight tube and which color o-ring is used. Hate to go through all this and put on the wrong o-ring. I ordered the Melling pump, gasket kit, and crank bolt. Should be good to go this weekend.
 
ruckus520 said:
I'm having the same issue and I did the o ring on the pick up tube last year, and did the oil pressure sensor last November but it was a duralast from autozone you think getting a AC delco will fix the code?
Click to expand...

What code are you getting? I never got a code, just the low pressure warning which coincided with the analog gauge. Instead of guessing on the sensor, I would get a mech gauge and check what your pressure actually is. You can get the oil tester kits on Amazon for $20.
 
robertmee said:
I watched a few videos. It's a pain, but doable. You don't need to move the pickup tube so it can stay bolted to the windage tray inside the pan. You remove the bolt between the pump and pickup, which is the hard part. It's recessed an inch into the pan, but accessible with a skinny wrench and a magnet to hold it so it doesn't drop into the pan. Some use mechanic's wire to wrap the bolt and hold it also. You can also take the face of the pump off and remove the pump gears and that gives more play and room to remove the bolt. Once the bolt is out, you can remove the pump with a little twisting effort, then replace the o-ring on the tube that's now exposed. I think it's more of a pain because most are laying on their back trying to get it. I'll have mine on my lift and at eye level so I'll probably give it a whirl. Worst case I drop the bolt into the pan and have to take the pan off anyway.

In regards to the O-ring, do you know if the 2003 has the tapered or straight tube and which color o-ring is used. Hate to go through all this and put on the wrong o-ring. I ordered the Melling pump, gasket kit, and crank bolt. Should be good to go this weekend.
Click to expand...

I used the Melling Automotive Products M295HV324S Oil Pump that came with the correct o-ring and a new pick up tube and the oil pump.

I had read about others getting the wrong o-ring, so I just went for the complete kit with the correct parts.

I'm interested in hearing how your project goes.

Best of luck!

:) (y)
 
EXT4ME said:
I used the Melling Automotive Products M295HV324S Oil Pump that came with the correct o-ring and a new pick up tube and the oil pump.

I had read about others getting the wrong o-ring, so I just went for the complete kit with the correct parts.

I'm interested in hearing how your project goes.

Best of luck!

:) (y)
Click to expand...
Yes that's the same pump I ordered, minus the tube, and it comes like that one...with a black ring and a green ring. Depending on what type of tube you have, you use the green thicker ring or the thinner black ring.
 
Quick update. Got down to the oil tube and what a pain. Got it off then promptly dropped it onto the pan. Got it with a magnet then dropped it again. Took that as divine intervention and decided to go ahead and remove pan. It really wasn't that bad. Took maybe a couple of hours and mainly because some of the bolts are a bear to get to. The upper differential bolt is a pain. The bolt on the side of the oil pan holding the transmission lines is a pain. That coupled with there has been years of oil leak covering everything in a layer of sludge. Taking the opportunity to power wash and degrease everything before I put it back on. Hate that I have the extra expense of an oil pan gasket and oil change again, but piece of mine to make sure the screen was nice and clean. Oil pan itself isn't bad. No caked up deposits inside....a little circle of crust in one area but otherwise nice and clean.

In regards to the major oil leak, it looks like from about midway down the timing cover on both sides and down the front/bottom of the pan. The harness that runs across the bottom of the time cover is caked in a half inch of oil. Doesn't look like valve covers. Inside of timing cover is clean. So where might all of that oil came from over the years and while everything is off any other gaskets or seals I should replace beside water pump, timing cover, crank seal and oil pan?
 
Welp....I'm thoroughly defeated.

Changed the oil pump, pickup, gasket, sender....expense of new pan gasket, timing gasket and water pump gasket. Two days of cursing all the oily mess. Got it back together and exactly the same behavior. Which means nothing was wrong with any of the aforementioned pieces. I can only assume a spun bearing?
 
robertmee said:
Welp....I'm thoroughly defeated.

Changed the oil pump, pickup, gasket, sender....expense of new pan gasket, timing gasket and water pump gasket. Two days of cursing all the oily mess. Got it back together and exactly the same behavior. Which means nothing was wrong with any of the aforementioned pieces. I can only assume a spun bearing?
Click to expand...

I don't see any post mentioning that you checked the oil pressure with a mechanical gauge. Maybe it's your pressure gauge stepper motor and not the oil pump pressure at all and the ticking is just a typical lifter tick that these "new" non-best-motor-created-350 makes (or a sticky lifter that would be much louder until it releases in which case you need a quart of MMO)?
 
2003VAAV said:
I don't see any post mentioning that you checked the oil pressure with a mechanical gauge. Maybe it's your pressure gauge stepper motor and not the oil pump pressure at all and the ticking is just a typical lifter tick that these "new" non-best-motor-created-350 makes (or a sticky lifter that would be much louder until it releases in which case you need a quart of MMO)?
Click to expand...
That is true....however no freaking way I'm taking that sender out the back again. Broke two, my arms are raw, my back is broke, and I don't have the heart right now to contort myself again trying to get a mech gauge in there. Is there another place to tap into more accessible?

Thinking about it further, I'm getting the low oil pressure message on the dash that coincides with the pressure dropping to 5 psi at idle and the bing bing bing. That should have nothing to do with the stepper, correct?

Can I use the gallery plug on the front of the block drivers side? Its usually used for priming the oil pump. Or one of those oil filter adapters used for turbos
 
Last edited:
You must log in or register to reply here.
Back
Top