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Old 04-15-2012, 09:50 PM
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4.7 Burning Oil, No Suction from PCV Valve?

I have a 2001 GC 4.7 with 186k. It has been burning oil for year and a half now. I have switched to Castrol High Milage 10W40 and a quart of Lucas Oil Stop Leak at every oil change. It was burning a quart every 2k, but now it has declined to 1/2 a quart every 3k. I decided to change my PCV valve this weekend and went to AutoZone and picked one up for $5. I removed the valve and replaced the 3/8 rubber hose to connect the valve and line. I did dig out some gummy oil substance from the oil filler tube where the valve goes. Once I installed the valve to the oil filler tube and then the line, I cranked up my vehicle. I placed my fingers in the oil filler tub down to the opening where I should have suction, and no suction at all. Does anyone have any ideas?
Could the oil filler tube be clogged up or possibly the line?
I purchased some carb cleaner, is it safe to spray in a little in the oil filler tube?
Any suggestions?

I'm pretty sure the oil being burned is coming up through the valves. Could a clogged PCV valve area help cause this?

The top of my engine stays dirty from a soot type substance. I think this is the oil being burnt, but where is it coming from?
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Old 04-16-2012, 03:36 PM
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Re: 4.7 Burning Oil, No Suction from PCV Valve?

At the firewall end of each valve cover towards the intake, you will find a rubber elbow which is only a few inches long. Check to make sure these aren't split. Common problem with the good ole 4.7's.

Note: It's not the easiest to get your hand back there much less see with the naked eye. It's best to check the above mentioned on a cold engine.
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Old 04-16-2012, 10:14 PM
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Re: 4.7 Burning Oil, No Suction from PCV Valve?

If you want to be sure that the PCV line is open, just disconnect the hose from the PCV valve and start the engine. It will run at a higher idle, but thats no problem. Feel with your finger if you have vacuum at the line, it should be strong. If not, there is some blockage in the line towards the inlet duct. Also not sure if a not properly working PCV system would increase the oil consumption (could be if PCV valve was sticking open), but at least it can cause sludge and other buildup due to the blowby gasses which canīt go anywhere in the block and will mix with the oil.
My 4.7 was burning oil as well and i also changed the PCV valve. No cure. Finally changed all the valve stem seals (hell of a job with engine in place) and the problem was solved. Take care in using thicker oils and additives. It could slow down oil consumption, but it can also lower the pressure/flow at the bearings (more pressure losses in the canals due to the higher viscosity) and compromise the lubrication.
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