S8ER95Z

iTrader: (3)

Just starting having this issue and looking for some direction... anytime I engine brake to come to a stop (1st gear down from 30ish) I will get light blue smoke for a few seconds from the exhaust AFTER I've come to a complete stop. The car has always had piston slap issues and oil consumption (I have a catch can, still lose a quart every few thousand miles) so my first guess is rings? I have also heard that it could be bad valve seals? Car is driven aggressive during the summer with a lot of 'road race' action (high rpm holding through curves), a hundred or so 1/4 passes and driven all winter with a pretty light foot. Any thoughts?

153K on the car... LS6 Cam, LS2 lifter trays, LS6 lifters, LS6 Yellow Springs, 7.425 pushrods everything else internal is original/stock. Other mods in sig.

Exeodus

iTrader: (1)

My guess would be rings, leaky valve seals usually cause the blue smoke on a cold startup because enough oil accumulated in the chamber to create the smoke. During normal driving, the small amount of oil isn't enough to create blue smoke.

S8ER95Z

iTrader: (3)

Would a ring be symptomatic at WOT? It seems to only do this immediately after engine braking.. but it's possible it's happening WOT and I just haven't noticed. I'll do a leak down/compression test this weekend, just wondering if there is any other signs I can look for here.

Thanks for the reply.

SSCamaro99_3

iTrader: (1)

Unless actually road racing, I would skip engine braking to every stop. It's not like these cars have drum brakes on all four corners. Brakes tend to be cheaper than clutches, slave cylinders, piston rings and so forth.

S8ER95Z

iTrader: (3)

It's just a really bad habit I've had for a long time... I've been trying not to do it at all, especially with this going on.

SSCamaro99_3

iTrader: (1)

I think GM even has a section in the owner's manual that states not to engage 1st gear when moving above a certain speed (I want to say 10-12 mph). I have driven a old Chevelle with drum brakes on all four corners (felt like the car would never stop), and can see where this may have had a use at one point in time. However, like leaf springs on passenger cars, those days are gone.

S8ER95Z

iTrader: (3)

heh my 1st is good up to 55mph.. it gets engaged over 10-12mph all the time. lol With 152K and the very short list of parts I've replaced it couldn't have hurt that much.

SSCamaro99_3

iTrader: (1)

I know what its good to. Considering you are blowing blue smoke out when you do it, I would beg to differ on whether or not you have hurt it.

S8ER95Z

iTrader: (3)

Fair enough.. doesn't help me find the problem though. lol

SSCamaro99_3

iTrader: (1)

Rings are your most likely culprit. When the C5 Z06 came out GM had to change the rings becasue they were getting blowby on decel. I think all subsequent warranty and dealer work for LS engines specified the new rings. Been a long time since I read about it on here.

S8ER95Z

iTrader: (3)

Thats actually a huge help.. This is all really recent and I put the LS6 cam in at 138K, headers on at 149K... (I do 25K a year so it hasn't been all that long). I will have to do some reading.

Thanks

Edit: I'm seeing a lot of comments about smoke during acceleration = rings, decal or startup = valve seals. I might be ok here.

I modified my original post.. the smoke doesn't actually start until I'm completely stopped (stop light) then last for just a couple of seconds. Doesn't appear to do it any other time.

Exeodus

iTrader: (1)

Are you only checking while driving the car then looking in the rearview, or have you followed your car while someone else drives it to see when the smoke is coming out? Just because you only see it after you stop doesn't it isn't happening all the time.

S8ER95Z

iTrader: (3)

Yeah I had the wife follow me for a good hour and nothing. Thinking of mounting a hopes back there to see if anything causes it other than decel/engine braking.

Redbull87

iTrader: (3)

Rings wouldnt be a bad idea with the mileage on the motor,same for valve seals.Its due for some freshening up.Plus id take the intake off and spray it clean on the inside..pcv's on these cars are well known to suck from factory and have oil residue inside the intake.Since you drive hard..and drive alot...Im sure you might regain a bit or power if not more efficiency by doing both while your motor is apart.Just my opinion.

bww3588

iTrader: (49)

Blue smoke on deaccel is definitely rings and/or valve seals . Your throttle is closed and your putting a vacuum in the cylinders and intake. Air is going to try to push in from everywhere it can, including past the rings and valve seals. I'd put money on rings over valve seals simply because the amount of oil under the piston is greater than what's laying around the valve seal. However, with the high mileage of your engine, I'll bet both are shot.

S8ER95Z

iTrader: (3)

After catch can so far so good, no smoke incidents but catch can has been filling faster than expected.

Pulled plugs... All of them look almost brand new except #7

Tested the wire and replaced the plug... Will see what happens now.

bongva

iTrader: (7)

Had the same problem in a similar car. when I would coast down hill in gear, as soon as you just get on the throttle a little it smoked blue smoke. Ended up being a burnt valve wasn't sealing correctly. Oh and yes it was eating oil too.

S8ER95Z

iTrader: (3)

Compression test done today...

all between 185 and 190 with 4 rotations.

Now I have no idea what to think.

bww3588

iTrader: (49)

Did you do a wet compression test after the initial compression test?

S8ER95Z

iTrader: (3)

I did (been outside all afternoon tearing into this thing). I got almost identical numbers with the wet test (less than 5 difference).

I did discover a bad plug wire on number 7 which would explain why it doesn't look like its been firing properly. The metal contact is halfway up the boot and the plug wasn't making contact with it. I noticed when I plugged wires back in that it wouldn't click. I'll be replacing it and seeing if that does anything or is just a red herring.

Also noticed a pool of oil around the #7 valves long after the engine was done running. Shouldn't that have drained back?