'09 5.3 No oil pressure. No oil. No sign of leak.

[PatDTN]

Never showed more than a half quart of usage over 5000 mile changes. Truck's at 220k miles. Any known types of issues?

 

[OR VietVet]

So, you are SHOWING no oil pressure and you have engine noise from that or you have no noise? You say, "no oil". Do you mean no oil in the engine or no oil showing on dipstick? The dipstick only reads the top 2 quarts of oil in the pan. Showing no oil leaks and that is good. If you have oil in the pan and shows at or close to full and you have no engine noise, then I would suspect the oil sender.

https://www.rockauto.com/en/moreinfo.php?pk=4631781&cc=1442911&jsn=2274


You could also have the dreaded oil seal at the oil pickup in the oil pan problem. But if you are hearing no abnormal engine noises then I would rule out, for now, an actual loss of oil pressure.

 

[PatDTN]

The oil pressure comes up at startup then bleeds down rapidly to 0 . It was pouring rain outside and I didn't hear anything but that.

When I got the warning to shut off the engine indicates and coasted until I had to get up a hill and restarted. Oil pressure came up but dropped pretty quickly. I had to climb 3 short hills to get home. I was down to no pressure backing in to my garage and shut it off quickly without listening for a noise.

The dipstick showed no oil but clearly there's some. I need to get some oil to add and see what happens from there.

 

[PatDTN]

Oh and thank you for your service !

 

[OR VietVet]

I would first replace the oil pressure sender because it is the easier thing to do and add oil and look for leaks. You may be burning it so during the next start up look for blue smoke indicating valve guides and seals problems. Then during a roadtest look for hard accel blue smoke that could indicate rings problems. You do have 220k miles after all. I would do a compression test if you see that smoke under hard accel. If you get any cylinders with at least a 10-15 psi difference, do a wet test on the low cylinders. That just means squirt a little oil in the low cylinder and run the compression test again. If the compression comes up then that means the rings are bad/weak and the oil in there helped seal the rings and compression came up. It can still run fine with either of these problems but when you pull the plugs, for compression test, check for burned oil on the ends/tips. Check the coolant for signs of oil sludge and check the oil fill cap for the sludge. If the sender does not fix the pressure reading problem then you may have the oil pickup seal leak that there are many threads about here at the forum. Time for some basic diagnostics.

 

[PatDTN]

Yeah. This place is good for my first step on anything with this Tahoe.

 

[OR VietVet]

I just added some more info to my last post about the compression test steps.

 

[PatDTN]

I need to get over a bad cold before I start in on this. I'll be able to add oil and see what happens. If it's okay after adding oil I'll just keep running it. Of course I'd love an excuse to swap in a 6.0.

 

[swathdiver]

Never showed more than a half quart of usage over 5000 mile changes. Truck's at 220k miles. Any known types of issues?

Pat, does your engine have an engine oil cooler? Are there 2 half inch lines coming out of the driver's side radiator tank? If so, look down near the power steering pump and see if they're leaking. We had a Pontiac that once every few years would consume all of its own oil very quickly and then run fine for years afterward. We figured it was all the rings on the piston lining up allowing the oil into the combustion chamber, never found out. Great little engine.

 

[iamdub]

Could you be so low on oil that there's just enough in the pan at startup for the pickup to suck it up and pump it into the motor, but the level drops when it sucks it up so then the pickup is no longer submerged and can't suck up any more, so the pressure drops?