New guy with an old Tahoe

[Webster]

I have a '09 Chevy Tahoe LTZ, FWD, with a 5.3L engine, & 176,000 miles. Its oil changes have been on schedule using Valvoline 5-30 full synthetic. Vehicle has had drive train maintenance and some front end work, a few years ago. It's never been in a crash. Last Winter I replaced the oil pressure sensor. There was no leakage around it. The vehicle has always run great. We are in our 70's and never abuse a vehicle. Last Saturday, after parking on a side street for two hours, I drove the 15 miles home with no issues. Sunday morning I discovered a large pool of motor oil underneath the rear of the engine. I inspected the front & both sides as best as I could without removing anything, and using an endoscopic camera. Nothing found. Next I crawled underneath, camera and lights, inspecting the rear of the engine. Oil covers the driver's side of the bottom of the engine, but I could not see a likely source. When I run the engine oil pressure is normal, fluctuating as engine speed rises and slows. I did not run the engine while I was under it. I drained the oil today, about 4 qts of the 6. My next move will be to remove the top of engine parts to gain a better view of the oil pressure sensor. But again, all the oil I can see is on the driver's side, and below the middle of the engine. My question: Is there anything that could have caused this that commonly occurred on these vehicles? Thanks!

 

[Webster]

Inspected oil pressure sending unit, no apparent leaks. Will tow it to a shop tomorrow. Still looking for an obvious cause that an old shade tree could fix. Ideas anyone?

 

[Mbdarkhorse]

Could be a rear main seal? Did you check the sending unit with the vehicle running?