2005 Silverado 5.3L Z71 162K miles smokes a bit at startup

Snowskier · February 23, 2015

Was hoping the forum could give me some insight on next course of action. My daughters truck in the title began smoking on startup afew weeks ago. It has had a very small oil leak that I thought was a rear main seal. I cleaned the underside of the engine this past summer and peeked inside the inspection plate of the bell housing. DRY. I would have thought a a rear main seal would have oil all over the inside of the housing.

I snugged the valve cover bolts and let it be. She never gets any low oil warning lights or chimes.

Fast fwd to the recent -10* days and I noticed it smoked on startup. Truck was down 2.5 qt. Poked around on the forum and found some threads about the clogged fixed PCV orifice in valve covers. Figured with 160K miles it was time for a peek under them. As you can see from the pictures they were due.

BEFORE

AFTER

COMPARISON

Could they have been so blocked that some oil backed up into the intake and that it what truck was burning? I have a long drive coming up this weekend with the truck and will see how she behaves. If it continues to smoke what would my next course of action be valve guide seals? Any thoughts would be helpful.

Daughter loves this truck. Nothing else mechanically wrong with it.

Thanks in advance,

Brad

sahls01gmc · February 23, 2015

Welcome to the site!

Have you tried any SeaFoam or anything similar? You're at about the right mileage where this stuff will start happening.

Snowskier · February 23, 2015

Yes on Seafoam. I ran a can of Mopar compustion Chamber cleaner thru it this past summer as well. Drilled a tiny fractional hole just the size of the red straw in the intake just in front of the TB. I was thinking of removing the TB and giving it a good cleaning with TB cleaner and toothbrush. I did that once a year on my Jeeps. I know the newer fuels are cleaner than the old days but I am still amazed how dirty the TB gets on modern cars.

This past summer when I drove it to Cleveland to get fitted for the Corsa exhaust with cruise at 62 its hand calculated mpg was 20.9. I was very happy with the that result with the high mileage.

I am very mechanically inclined. Are the valve guide seals something I could do in the garage? I have installed long arm suspensions, transmissions and TC in jeeps. This torsion bar truck was pretty foreign looking to me coming from solid axel world.

BigBadSierra · February 23, 2015

It's much easier to change the seals today. Look for a LS valve spring compressor tool.

These make it easy to change the seals out switch springs too.

Just make sure the piston is at TDC that your working on or it's bye bye valve.

Tools reasonably priced too around a $100 for a good one.

Snowskier · March 2, 2015

So after cleaning the valve covers, changing the oil truck went on a 600 mile trip over the weekend. I am happy to report that so far so the smoking issue is gone. I looked for it each morning when started and after sitting for a few hours.

3 adults, 200# of junk in bed, cruise at 65 into a head wind hand calculated mpg of 16.73.