Had my engine rebuilt in my 2006 Hummer H3 and have a significant oil issue. Orig thought it was an oil leak. Have figured out that instead, oil is sucking out of the PCV tube where I have highlighted in blue and running down the backside of the engine. Losing 4 quarts per tank of gas.

Any ideas?

 

Look for a blockage at #3 into the intake manifold. Take a good look at your exhaust and CATs.

 

Thanks Doc. So you are saying remove the manifold and check for a blockage specifically here? That could cause oil pressure back into PCV?

 

The spot you circled in your opening post #2 through #3 creates appx. 70% of the vacuum needed for your motor to stay balanced to avoid excess crankcase pressure. #6 into #1 handles the rest. Too much crankcase pressure is a prominent cause for oil leaks, but not the only cause. Seems to me, whoever rebuilt the motor did not diagnose the cause of you continuing problem, they just rebuilt the motor. I would be looking for a vacuum blockage in the crankcase vent system. Possible too much exhaust back pressure as well.

There is a "filter" (not directly serviceable) to catch excess oil so it does not get dirty oil back into the intake/fuel delivery segments of the motor. Plug the filter with crud and oil and it will find somewhere else to go, like yours is experiencing. In the I5s, think of the filter as like a wad of gauze jammed in the passages where the crankcase vents through #4 and #5. Blow some air through #3, #4 & #5, does it vent or is it very restrictive?

I have never seen/heard of one so bad as 4QTs per 300 miles, but it is an easy check.

 

Thank you very much Doc. My mechanic is a chev expert and I have shared with him. Will advise resolution.

 

My mechanic worked w a GM specialist and they have determined that the baffle in my valve cover (red color) is clogged and cannot be fixed/cleaned. I therefore need a new valve cover. Issue is no one stocks valve covers for the 3.5L. GM NA says not avail and discontinued.

Anyone have any leads on where I can source a 3.5L valve cover? new or used is fine. Much appreciated.

 

Thought so.... lucky guess. Gonna need the gasket too. Check my link and then add in the PN below, shows 3 available. GOOD LUCK.

Engine Valve Cover Part Number: 12591996

http://oemcats.com/oem-parts/12591996.htm

# 518

 

Anybody confirm the 2007+ Valve Cover fits the 2006? It should, it is just not black, but it would be good to know for 100% sure.

 

And, you can clean out the Crankcase baffle after removing the Valve Cover. So when your "mechanic" says can't be repaired, tell him I call BS. Others have done it.

 

I ordered a 2007 (desperate) and can confirm the 07 does not fit on the 06.

I called all 3 above sources that had online stock. All say discontinued. Next step, I will remove the cover and attempt to clean tehebaffle. My mechanic is suggesting drilling holes to allow breathing. He says he tried with hot bath etc.