black00chev

iTrader: (2)

My 5.3 has 153K as well and I check the catch can every few weeks as I always do to make sure my intake is stayin tight and such, and will only fill a bathroom size dixie cup less then 1/4 of the way.

BMRisko

Well...no change from relocating the catch can. The can was full after 120 miles. Guess the next step is a compression test and pulling the driver side valve cover to see if something is clogged under there as suggested earlier. Ugh...

What is the quick and dirty for doing a compression test? Never done one before, but I picked up a tester at the local parts store in anticipation of doing one.

BMRisko

I assume this is as good a step-by-step as any?

1. Charge the battery if the battery is not fully charged.
2. Disable the ignition system.
3. Disable the fuel injection system.
4. Remove all of the spark plugs.
5. Block the throttle plate wide open.
6. Start with the compression gauge at zero, and crank the engine through 6 compression strokes (6 puffs).
7. Make the compression check for each cylinder. Record the reading.
8. If a cylinder has low compression, inject approximately 15 ml (one tablespoon) of engine oil into the combustion chamber through the spark plug hole, recheck the compression and record the reading.
9. The minimum in any one cylinder should not be less than 70% of the highest cylinder. No cylinder should read less than 100 PSI. For example, if the highest pressure in any one cylinder is 150 PSI, the lowest allowable pressure for any other cylinder would be 105 PSI.

BMRisko

Yea, I'm pretty sure my situation is not normal. How do you have your can routed?

eallanboggs

iTrader: (1)

You're allowing way too big of a window on your compression readings. Close the window down to 15%. It's a good idea to have the can mounted BELOW the intake port so solids(oil and water) stay in the catch can. Having the can mounted low down makes it harder for solids to migrate up the hose and into your intake. Smoke on start up is usually attributed to the classic worn valve stem seals, but in your case there appears to be more is going on. A compression test is a starting point, but a leak down gives more specific info. If some cylinder fail the compression test do a leak down on them. Pull the filler cap or dipstick and listen for air escaping. You could hear air at the tail pipe(exhaust valve), air coming out of the throttlebody(intake valve-intake plenum must be removed and throttle blade partially open) air coming out oil filler cap or oil dip stick tube(rings) or bubbles in the coolant resevoir(head gasket). If you have done your routine maintenance since the engine was new and you do NOT spray your rings should last more than 150K miles. The catch can is a good idea, but your getting way too much oil in there. I'd pull the plenum and throttlebody to get a good look inside of the intake manifold. Shine a bright lite in there and I doubt you're going to be please with what you see. Now just imagine mixing that gooey, slimy, milky slop with the soot that also feeds back into the intake from the EGR system and you've got a real mess on your hands thanks to the EPA. A catch can and an EGR bypass is a good idea and your intake will thank you.

BMRisko

Thanks for the reply...that compression test steps were copy and pasted from another site and after re-reading I agree that 70% looks way to high. The catch can is still mounted slightly below the intake, so I should be good there. If the ring was that bad earlier, wouldn't I have noticed a lot more smoke when driving or massive oil loss?

Also w/ the catch can, could it somehow be creating a stronger vacuum and pulling oil through? I've had the vehicle since 65k....been running 5w-30 synthetic and maintaining it ever since then. It is a daily driver and never gets pushed too hard, nor do I tow a lot. It does see a lot of highway miles. Nothing looked abnormal w/ the oil, nor did I notice any sludge when I purchased the vehicle. It has always been naturally aspirated, so what could lead to a ring failure (assuming that's what it is) at 150k miles? Only engine mods are intake, exhaust and tune...nothing extreme.

I guess the next step if it fails the tests is a replacement vs. re-build. I would think w/ replacing rings, valve seals, head & intake gasket (and pray the head isn't warped or cracked), I'd be pushing the cost of a crate LS327 (I know no one is a fan of them on here, but I need something I could drop in and won't have time or transportation to re-build my current motor). With everything that I would replace, a 0 mile motor is appealing.

eallanboggs

iTrader: (1)

You said you have a puff of smoke at start up. That points to the valve stem seals. See how the compression test goes and if it fails do a leak down. The vacuum is created by pumping action of the pistons not by the catch can. High vacuum(pulling oil from the crankcase) points to good sealing which says your rings are good. If you had poor sealing your vacuum would drop not increase. This is a strange one.

BMRisko

Glad I'm not the only one who thinks that...I probably won't have time to do a compression test until this weekend. I have been losing coolant extremely slowly though. I basically have to bring the tank from half full to full every couple of months. I guess head gasket is always a possibility...since I have checked hoses, replaced WP and gaskets and replaced surge tank cap. That may be an unrelated issue though.

FWIW, oil on my dipstick looks brand new and the oil in the catch can is black, w/ a slight shimmer on top. Looks to be some extremely small and barely noticeable metal flakes in there also, maybe enough to cover the tip of your pinkie. Fluid from the can has a slight gas smell too, not straight oil.

skolman91

iTrader: (28)

there is a tsb out for slow coolant loss like yours which involves bad heads. I believe they have a tiny battery symbol behind one of the rocker posts under the cover. Search around to see what im talking about, some other member had the exact same problem and made a thread about it i think..

black00chev

iTrader: (2)

Here is a pic, the can is from www.catchcans.com