Smoking under Engine Braking?

[edin]

My goon is running really well. Just tested compression and cylinders 1-4 are 162, 168, 175, and 165 psi so pretty even across the board. I first noticed that my car will put out some white smoke as I get back on the gas after hard engine braking when I was engine braking through the twisty napa hills. So I've been watching it, and sure enough, almost any time I engine brake, it lets out some white smoke after getting back on the gas. No matter how hard I get on the gas during normal driving, I can't get any smoke to come out, just after engine braking.

 

Any thoughts...?

[flatcat19]

Stop downshifting?

[ProjectFeint]

Have you checked for oil consumption? sounds like your getting blow by... Maybe worn valve stem seals or piston rings.

[datzenmike]

Two things.

 

Extremely high manifold vacuum, which is normal when engine braking, will suck oil up past the rings and down through the intake valve guide seals.

 

Hard cornering and braking can slop oil from the pan onto the crank and or the cylinder walls. The rings can't handle it all and it gets into the combustion chambers.

 

Engine braking is used in racing to conserve brakes and to keep the revs up for coming out of a corner. You're not in a race so use you brakes more.

[Z-train]

Odds say valve guides/seals.

[Draker]

Odds say valve guides/seals.

 

This

[DanielC]

Odds say valve guides/seals.

 

This

 More this!

[wayno]

When my valve guides/seals went bad, I really did not notice it much out the exhaust pipe when driving, when I seen it was when I added oil in the morning, it leaked down past the seals/guides when I added it, and when I would start it, it would smoke for 5 minutes till it burnt it out of the cylinders, it was on fast idle, so a significant cloud was created.

That engine still ran smooth, it just used a lot of oil, it did mark it's territory a little, but mostly it burnt it, although it did not look like it was burning oil under normal driving.

[izzo]

Two things.

 

Extremely high manifold vacuum, which is normal when engine braking, will suck oil up past the rings and down through the intake valve guide seals.

 

Hard cornering and braking can slop oil from the pan onto the crank and or the cylinder walls. The rings can't handle it all and it gets into the combustion chambers.

 

Engine braking is used in racing to conserve brakes and to keep the revs up for coming out of a corner. You're not in a race so use you brakes more.

 

 

I'd guess the first. The motor is a year old, all new parts. nothing was re-used., nothing...  All bearings, rings, guides, seals, pumps (all three) like everything was replaced. all new bolts all holes cleaned up...  The motor is fresh as they get. probably about 20k ish on it right now maybe a little more...

 

It was fine in Adams truck, then went in the goon.  I'd guess high vacuum on the intake. I noticed it on the car, too.  tried to diagnose it and said to hell with it.  It wasn't bad enough when I had it for me to worry about it.  Everyone said just drive it, it's fine. It has all new gaskets and things blocked off where need be, but you can hear a hum in there when she's running.  I heard the same hum on the other motor with this intake. Maybe swap intakes?  Idk, but I wouldn't engine brake either.  Letting off the gas a little to slow down some is one thing but dropping gears isn't needed.  Brakes are there for a reason, also.. Don't run the piss out of that dogleg. IT WILL BREAK.  I hell ran my orange wagon down some back roads with a dogleg... Dropping gears, revving it out, slamming gears,,,, come up to a corner drop a gear, punch it on the second half...  Bam, went to switch gears and the gear shifter was stuck. That trans has been forever screwed since... They are a pain to rebuild.  Doglegs are fine in teh wagon to get you around and have some fun, but rippin n tearin they dont like that :lol:  Grab a driveline out of a sedan, and a 280zx five speed. Then do it :rofl:

[MikeRL411]

Old mechanic's wisdom.  Brakes are cheap, transmissions are expensive.

[Draker]

If seals are good... excessively worn valve guides. Unless head was completely rebuilt and guides were addressed.

[Draker]

I'm sure this guy doesn't go around engine braking all the time.. but it does happen now and then and that's probably where he notices it.. especially when diagnosing the issue. Your problem is in the head.

[datzenmike]

Check the oil level too. Over full and hard braking and down shifting can slop oil to the front of the pan and up onto the spinning crank. This whips it into a mist or fog of oil droplets. These can overload the block vent screen and be sucked into the PCV system.

 

Just foe the hell of it pull the hose off the PCV valve and try it.

[izzo]

The head was rebuilt. I'd be surprised

[edin]

Hey everyone

 

Despite my absence from this tread, I really appreciate all the thoughts and suggestions. Been a bit crazy at work and haven't had much time to stay up on the forum. Anyway, I was engine braking probably (definitely) more than I should be. I moved to the goon from a 40 year old truck that wouldn't let me downshift so...what can I say, I've been having fun. Anyway, I'll keep the downshifting to a minimum. Kinda hard to monitor oil level because it's leaking quite a bit as it stands.

 

Thanks!

[Trophy24]

I agree with the above posts. 

It sounds like oil is entering the combustion chamber through the intake ports.  The source is usually the valve guide, but as stated above can also be the pcv.  Look for oil deposits on one side of the spark plugs.  This would confirm oil mist coming in  through the intake valve.  When I have seen oil control ring issues, the deposits on the plugs are evenly distributed.