Blue smoke

[ChrisWhewell]

This is weird, but if my '90 sits for two weeks, when I start it up and drive it away, I get blue smoke out the tailpipe for about half a minute, or 500 feet of driving.  Then, the blue smoke goes away.   This happened last summer when I had the car jacked up and was doing the struts.   It was blue smoke when I got it running again.

 

Then, a couple days ago, except this time the car wasn't jacked up.   It had only been sitting in the garage.   I started it and drove and noticed, a moderate amount of blue smoke. But the blue smoke stopped after about 500 feet of driving, just like the first time it happened last summer.

 

So, I'm wondering what the mechanism might be.    Is it an oil ring ?   Or is there some place in the motor that oil seeps to, and accumulates ?    It doesn't seem likely that it'd be a valve guide seal, but I admit I don't have a clue.      Any thoughts appreciated.........    The motor only has 80l on it.

Edited December 29, 2016 by ChrisWhewell (see edit history)

[Ronnie]

It's most likely a valve stem seal(s). Over time when the engine is off the oil runs down the valve stem and puddles behind the valve or on the top of the piston. When you start the engine it takes a minute to burn it off.

 

I don't know about the 3800 engine but on some engines this can cause a problem other than the blue smoke. On older small block Chevy engines for example the oil can run down the valve and drip on the hot spark plug electrode causing deposits to build up on the spark plug and eventually cause the spark plug to miss.

 

Even at low mileage the seals can get hard and brittle or crack after so many years. I've known this problem to be made much worse if the oil return passages in the heads a partially blocked so oil stays puddled in the head around the seals. In the old days the blockage was commonly caused by using paraffin based oils like Quaker State. I'm guessing that most modern oils don't have that problem but I still wouldn't use Quaker State oil myself because I remember how it could gum up an engine inside.

[bikemikey]

Ronnie, 

What do you think about "Bar's Leak"  for that problem ? They make a product just for that , maybe just temporary to see if that's the problem. 

[Ronnie]

21 minutes ago, bikemikey said:

Ronnie, 

What do you think about "Bar's Leak"  for that problem ? They make a product just for that , maybe just temporary to see if that's the problem. 

 

I didn't realize they made that product until you pointed it out so I can't comment on how well it would work. I do use a small amount of the Bars Leaks in the radiator of all my cars when I change the coolant to help prevent corrosion and to lubricate the water pump. I think they make good products.

 

I read about the valve stem repair product on their website. It appears they intend it to work by softening the seal and by forming a film on the valve stem seal to help stop the oil getting past the seal. If I had a high mileage engine I might try it, but on a low mileage engine (assuming the rest of the car was in nice shape) I would replace the valve stem seals to fix it the right way. I don't put much stock in magic cures unless I have first hand information that they really work.

 

If it were me I wouldn't do anything if the the blue smoke only happens every now and then assuming the engine is running good and isn't using a lot of oil. I would save my money until something big happens.

 

 

 

Edited December 29, 2016 by Ronnie (see edit history)

[Barney Eaton]

I had a Chevy truck that had a valve guide problem and used about 1 qt of oil per 500 miles, the strange thing was it never smoked.  Seem the catalytic converter would catch most of the smoke....possibly different types of converters work differently.

[ChrisWhewell]

Thanks yea'all.   Its acting as if some amount of oil is puddling up or seeping, as one wrote above.   For if it merely sits overnight or for 2-3 days, the blue smoke doesn't happen.  What i could do, is let it sit for a couple weeks, and run it 1/2 the distance it drives before the smoke quits.   Then, pull all the plugs and inspect to determine which cylinder the oil's burning in based on plug appearance.   Maybe there's a bad stem seal on a valve, but given the angle of the heads its unlikely to me that oil could get into the space btw the guide and valve stem - it would have to climb up the guide, against gravity.

 

another possibility is the tappet oiling system bleeds down over time and when started, more oil is getting squirted towards one of the stem seals than the others, until those galleries in the oiling system get fully pumped up.  I've seen many times some lifters get more oil than others for whatever reasons on most engines , due mostly to the nature  and geometry of the oiling system.

 

another possibility might be a hose in the PCV system, in which oil puddles in a hose over time and then gets sucked in at startup and blue smoke comes out until its all been burned.   Or maybe its somehow leaking into the emission control vacuum cannister and blue smoke comes until it gets evacuated from there after startup.

 

I was just wondering if anyone else may have noticed a puddling potential anywhere in the PCV or other emission control hoses, etc.

 

As for the recommendation to run transmission fluid - yes I know from my days as chemist at Lubrizol that all of the transmission oil packages contain what is known as a seal-swell additive.  I'm hesitant to run that because there are many seals in the engine and once you swell them, that's all you get - one swell spell.  Transmission seals are made of a particular type of polymer that is engineered to withstand constant exposure seal-swell additives, including those based on sulfolene-derived intermediates, which many are, and that's no secret.  But I lack knowledge that all seals in the engine were engineered to be exposed to seal-swelling additives and remain apprehensive of using the trans fluid in the crankcase.  

 

I bet the answer to this is relatively simple, I'm hoping its just the geometry of a hose which can be remedied by bending whatever hose it might be, a diferent angle to prevent the puddling.  Or, if its the vacuum cannister that would be seemingly easy.  Maybe I need to change the PCV valve - I have a new one I got from Ronnie but read horror stories about the existing grommet around the PCV valve  crumbling when one removes the PCV valuve, and am not in the mood for any car repair at the moment !!    Hey, how hard is it to change the grommet that the PCV valve sits in ?   Am I overly-worrisome ?  Is it an easy grommet swap ?

[2seater]

Agree the smoke on start up is most typically valve seals. I suspect the reason it can be seen at first is the cat. isn't up to temperature yet. Do the simple things first, the PCV is a good idea but there is really no hose involved on the 3800, just the valve inserted in the grommet and another grommet with a short hose type extension for the other end. Changing the grommet isn't the worst, but the location does make it difficult. Even if the grommet comes apart, there isn't a great danger to the engine since there is a pan on the underside of the intake manifold and the air to be sucked up by the pcv enters the pan on the other end through a couple of 3/8" diameter holes. One other possibility, although rare, would be from the vacuum modulator on the transmission. Easy to check to see if there is oil in the line.