why am I blowing plumes of smoke????

[n/a]

I have a 1969 280sl.  it seems that once the air temp outside got over 70F, I started to notice an increase in smoke out the rear.  when I let the engine deccelerate as I approach an intersection, it REALLLLY blows smoke when I accelerate on through.  I mean a biggg plume.  this is odd, cuz it did not happen at all in temps below 65F, or thereabouts.  can anyone help me out on this?  I am using straight 30W oil.  should I be using a heavier oil?  I even seem to be dripping more now too.  I am so depressed over this...  only had the car two years.  thanks eveyone for your input...  jp

j prothero
1969 280sl in Pitt, PA

[waltklatt]

J,
Let me guess you have an automatic?  If so, then your vacumn modulator is leaking transmission fluid to the combustion chambers to create white hazy smoke.
Remove the small banjo fitting that attaches the transmission line to the intake manifold and see inside if it's wet with a reddish oil.  
There's your culprit.
Walter

[Bearcat]

i think you may be due a serious shop visit...could be the piston rings are worn. Flip side is when you get it fixed you should have years of endless motoring.

[n/a]

OK walter... I will look into this.  but let me ask you... what oil do you think I ought to be using.  I am almost sure the manual says straight 30W.  I see some guys using heavier stuff, too.  what do you think?  is there really any truth to heavier not blowing past the rings as much?  --jp

j prothero
1969 280sl in Pitt, PA

[waltklatt]

J,
I think the oil that people use varies, some use regular dino oil and others use a synthetic or blend.
I use the W10-40 oil as it was for a wide range of temperatures.
In the winter you dont want heavy thick oil when cold, hence the low # like a 5 or 10.
What color is the cloud of smoke?  Does it only happen when you deaccelerate?  How about the coolant, is it wet in the engine bay around the reservior, oil in the coolant, or water in the oil?  (signs of a head gasket failure)
Walter

[rwmastel]

quote:Originally posted by jhpcat

I have a 1969 280sl.  it seems that once the air temp outside got over 70F, I started to notice an increase in smoke out the rear....  only had the car two years....

 - Did it do this last summer when it was hot outside?
 - What color is the smoke?
 - Do you know for sure how many miles are on the engine?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[ja17]

Hello j,
Walter has a good point here watch out for the transmission modulator diaphram.

First, check your fluids, you will be using something (oil, trans fluid, coolant) this will give you a place to start. Next remove your spark plugs and read them. A hard crust on any will mean oil burning through the rings or intake guides. Black velvet looking plugs are rich fuel mixture. Wet slimmy black or clear can be coolant or fuel fouled.

If you are using oil and not oil fouling the spark plugs the problem can be exhaust guides in the head. The oil simply is dumped in the exhaust manifold, never coming in contact with the plugs.

As Walter mentioned, if the problem is the trans diaphram, the transmission fluid may end up in the intake manifold and will foul #6 spark plug. The vacuum line going to the transmission will be wet with fluid inside.

Keep us up to date, we'll guide you!



Joe Alexander
Blacklick, Ohio

[n/a]

Boy... I sure am pleased withg this forum/board!  thanks very much guys for the input.  this was my first post.  I dont know how many miles are on the engine for sure.  the engine was replaced and the speedo says 75K.  but who knows since there is not 100K digit.  the car was represented as concourse.  thats not the case.  I blew a head gasket soon after buying it on july4 weekend two yrs ago.  was not used to have to be looking at guages instead of warning lights.  when I realized I had a problem, I pulled over and water was still squirting out the rad hose.  so I didnt run it dry.  had head rebuilt as it was out.  new guides and seats too.  car runs well but smokes like an indian smoke signal machine when I decelerate letting the engine slow the car as I approach an intersection.  The blast comes when I accelerate strognly through the intersection.  stuff like that.  it does not happen when outside temps are 60 or below.  I only drive in 50 and up weather.  smoke seems blue to me.  I just dont get it.  the engine must run hotter on 90degree days than 60degree days.  and thats enough to do it.  does this add up?  if I am using oil and not fouling the plugs, will this oil still end up burning as blue and come out the exhaust?  and since the head was rebuilt, shouldnt the guides be fine?  (I'll take another Prozac while I wait to hear...)

j prothero
1969 280sl in Pitt, PA

[A Dalton]

I have seen on rare occasion a problem simular to yours that turned out to be , of all things, a master cylinder leaking back into the brake booster over a long period . It actually got to a  level that
allowed it to be sucked through to the intake and would blow smoke after a throttle close like hell.
 The earlier chassis actually had a drop trap in the line where one could see this..
..anyway, if one keeps having to top off the master fluid res over time with no apparent leaks and doesn't know where the fluid seems to vanish, this is where it winds up. You would be surprised if you stuck a tube into the vac hose connection port to the bottom of your booster and put some hand suction to the hose.. you just may find a bit off brake fluid, and maybe a lot...
.. of course, it is much more likely that a trans mod of valve stem, etc . is the culprit, but this is a possible and I had it happen..

 A dead give away for master rear seal leak is the paint on the booster below the master mount starts peeling/rusting .. something not uncommon at all on these systems and something to watch for...

[Benz Dr.]

It's not the mod valve. When that goes you won't believe all the smoke you can have. The road behind me disappeared, the cars behind me pulled over and I couldn't see the shop or house when I pulled into the driveway. I was lucky that I was only a short distance from home because it pulled 2 liters of trans fluid in 3 miles. At night you might not catch something like this right away but the engine was barely running by the time I got home so it was clear something was wrong.

This sounds like a valve stem seal has popped off. Did you use new valve springs and/or new valves? Worn valves will make the engine smoke for some reason as well as low spring tension.
My thinking on this is that not only does the valve face wear but the stem and sealing areas wear too. A very good indication of worn valves is when you can't adjust the ball studs any more. You can get thinner thrust pieces or grind them down but this usually is an engine that will smoke.
I measure the valve depth minus the head thickness and add a valve spring shim if needed to keep the spring tension where it should be.

I think what's happening is the rocker arm starts to push on the valve stem if the valve stits too high in the head. This makes the valve guide wear and may actually open up a small gap on the seal where oil can leak into under vacuum. The rocker arm has an opening ratio that might also be affected by worn valves. In most cases the valve seats and head thickness seem to wear out at about the same time. I've never had to install valve seats because these heads were junk anway.




Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[n/a]

my car had exactly the same symtoms...I tried to power time the distributor to approx. 32 degrees and found that no matter how much I moved the distributor I could only get 30 degrees, I continued to drive car with no problems. I then set the point gap one day and also put about 6 drops of 20 wt OIL in the distributor felt just under the rotor...In less than 10 miles after a deceleration period and then applying the throttle again I was throwing plumes of smoke out the back. Putting a timing light on engine timing was found to be 54 degrees total..apparently weights in centrifigal assy were rusted stuck and oil freed them up causing this condition. Ignition was returned to 12 degrees initial & 30 total it now runs fine.

[ted280sl]

You have been presented with a number of excellent possibilities. Your challenge is to eliminate these possibilities until you find your cure. The most expensive fix would involve blown rings. I would suggest a compression check. It is a rather simple procdeure which could limit the possibilties and could eliminate your nightmare scenario. If your pressure is low it is either the rings or the head. If you have good pressure your rings are good. While doing the compression check you will be able to examine the spark pugs and they can help define your problem based upon the color of the plugs.
  Keep us posted on your progress.
Ted 1969 280SL
  I failed a compression check. It hurts!