engine and drivetrain Smoking on De-acceleration

[Timo02]

Greetings,

I *just* had a "valve/head job" completed on my '71 '02 and noticed that when driving the car home from the shop today that it smokes excessively out of the tail pipe a bluish/white smoke when de-accelerating. Then when I put my foot back into the throttle a larger puff of smoke briefly blows out the back and then it suddenly becomes *completely* smoke free. For me this is the classic sign on oil being sucked down the valve guides. The shop owner/chief mechanic ( a good guy) told me to bring the car back to him on Monday and he said that he will take care of it so I am confident that he will. The head work was sub-let to a machine shop.

One interesting data point is that it appears that the mechanic put in a synthetic oil (purple in color) in the engine when I normally run regular 20-50w Castrol (dino oil) and have never had the car smoke like this, even before the valve job. The mechanic told me the brand of oil which he used and it began with an "s" but I forgot the name and will ask him on Monday.

Here are my questions:

1)Could a cause of this smoking be the syn-oil and can this smoking be minimized by switching back to the dino oil?

2)Are there some kind of valve seals that fit in addition to the guides that can be installed to minimize this smoking?

All advice and feed back is very welcome. Have a great weekend!

[BrianC]

Greetings,

I *just* had a "valve/head job" completed on my '71 '02 and noticed that when driving the car home from the shop today that it smokes excessively out of the tail pipe a bluish/white smoke when de-accelerating. Then when I put my foot back into the throttle a larger puff of smoke briefly blows out the back and then it suddenly becomes *completely* smoke free. For me this is the classic sign on oil being sucked down the valve guides. The shop owner/chief mechanic ( a good guy) told me to bring the car back to him on Monday and he said that he will take care of it so I am confident that he will. The head work was sub-let to a machine shop.

One interesting data point is that it appears that the mechanic put in a synthetic oil (purple in color) in the engine when I normally run regular 20-50w Castrol (dino oil) and have never had the car smoke like this, even before the valve job. The mechanic told me the brand of oil which he used and it began with an "s" but I forgot the name and will ask him on Monday.

Here are my questions:

1)Could a cause of this smoking be the syn-oil and can this smoking be minimized by switching back to the dino oil?

2)Are there some kind of valve seals that fit in addition to the guides that can be installed to minimize this smoking?

All advice and feed back is very welcome. Have a great weekend!

Make sure and clarify that the valve guides were acutally replaced, and that the "new" style seals were used. I would run 20w50 dino in that mill.

There should be no off throttle smoke with a new head.

BC

[jgerry2002]

The synthetic oil would not cause something like this. If it is the wrong weight (too light) you can get excessive consumption.

Sounds like the guides/seals were not replaced properly.

Any good quality oil 15w-50 or 20w-50 is fine. I use Mobil 1 synthetic in all my cars with only good results.

[Timo02]

Thanks BC & Justin for the helpful feedback. At any rate I will let the shop take care of this issue. I didn't think running syn oil would cause this excessive smoking. The only main "side effect" that I've heard about syn-oil is that it gets by the engine and trans seals easier than dino-oil does. Thanks again and have a great rest of weekend.

Timo

[Timo02]

The saga is on-going. I have learned that the valve guides *were not* replaced but that the valve stem seals were. The mechanic claims that it could be the piston rings since the head was shaved and the compression has now increased so there is now blow by on de-acceleration because the piston rings are the "weakest part of the system..."

My questions are:

1) Is this possible that the rings are so worn and now causing the smoking on de-acceleration since the head is now freshly re-done?

2) What are the "correct" or "new & improved"valve stem seals to use and where can I get them?

Please Note: The engine did not smoke (either on acceleration or de-acceleration) before the head was worked on, now it smokes on long de-accelerations, for example when gearing down to exit a freeway. Then when you put your foot back on the gas-pedal to accelerate again a final puff of bluish smoke bellows out the tail pipe and then it all clears up and no more smoke until the next de-accelaration. The car runs "like a top" at all times too.

All advice on this smoky problem is very welcome and happy '02ing!

[mleach]

There is no way is it smoking on decel and not on accell and it still be the rings. You cant add enough pressure in the combustion chamber by increasing load byway of accell and it clear up your problem. Tell that guy that you paid for a service, and you would like it to be finished.

[winstontj]

Smoke on decel = valves

Smoke on accelerate = rings

Search the archives for a photo that CD posted of the GOOD valve guides, meaning the newer ones?? I forget but I want to say they are green/blue rather than black?? The BMW ones come with guide sleeves - excuse the vulgar explanation but they almost look like little condoms that you put over the top of the valve stems and then slide on the seals over the sleeve. This prevents the seals from getting nicked or cut on install. It's possible that everything was/still is in tolerance in your valve train only the seals weren't installed correctly and are now leaking.

Just a theory. Unfortunately now you're going to have to pull the head again to figure out what's going on - on second thought pull the plugs and look to see if only one is really bad. If so that's the culprit. If not when you pull the head have everything checked and put new seals on.

Good luck!

TJW