smoke
03-10-2006, 09:28 AM
#1
Burning Brakes
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smoke
Last fall I put thinner oil in my car for the coming colder weather. Since then when the car is warm and I pull to a stop I get more smoke than I would like. I will be putting thicker oil back in it shortly, but its acting a little strangely and I wanted to see what you guys thought.
Facts:
-90 c2 106k miles no engine work that I know of. (valve guides immediately get questioned)
-cat by-pass fitted
-Oil consumption before putting this thinner oil in was about 1 quart per 1500 miles.
-It will puff when its cold a bit if I don't let the engine run a bit before I turn it off. It never does it now that I do that.
-It does not smoke under hard acceleration
-It does not smoke at extended idle, or driving down the road.
-It puffs just a tiny bit of smoke when i back off the throttle (engine braking) only noticeable by a keen eye from a following friend. This doesnt bother me.
The problem that concerns me is when its been at elevated rpm, say 3000rpm or so, for a decent time and then I come to a stop I will get some visible smoke from the back, sometimes drifting around the side if the wind is blowing right. I'm not positive, but I think its coming from the exhaust pipe. None of the tell tails are evident for a drip. (As far as Ic an tell the engine is leak free). If you let it sit there a bit it will clear up. It will do this if I use the engine to brake to a stop or if I drop it out of gear and then brake to a stop. I cannot mimic this by raising the rpm manually and then letting it drop to idle. I see nothing. So I'm puzzled.
Sure the guides are probably worn, but it does not smoke using the engine as a brake going down long hills. Its just a tiny puff right as I lift my foot on the gas. Could something be splashing into the intake upon a slow down(force moving the oil forward)? No its not overfilled. In fact I let it get down about a quart below the bottom mark just to make sure. Same problem.
Again, I'm baffled. Anything thoughts?
Facts:
-90 c2 106k miles no engine work that I know of. (valve guides immediately get questioned)
-cat by-pass fitted
-Oil consumption before putting this thinner oil in was about 1 quart per 1500 miles.
-It will puff when its cold a bit if I don't let the engine run a bit before I turn it off. It never does it now that I do that.
-It does not smoke under hard acceleration
-It does not smoke at extended idle, or driving down the road.
-It puffs just a tiny bit of smoke when i back off the throttle (engine braking) only noticeable by a keen eye from a following friend. This doesnt bother me.
The problem that concerns me is when its been at elevated rpm, say 3000rpm or so, for a decent time and then I come to a stop I will get some visible smoke from the back, sometimes drifting around the side if the wind is blowing right. I'm not positive, but I think its coming from the exhaust pipe. None of the tell tails are evident for a drip. (As far as Ic an tell the engine is leak free). If you let it sit there a bit it will clear up. It will do this if I use the engine to brake to a stop or if I drop it out of gear and then brake to a stop. I cannot mimic this by raising the rpm manually and then letting it drop to idle. I see nothing. So I'm puzzled.
Sure the guides are probably worn, but it does not smoke using the engine as a brake going down long hills. Its just a tiny puff right as I lift my foot on the gas. Could something be splashing into the intake upon a slow down(force moving the oil forward)? No its not overfilled. In fact I let it get down about a quart below the bottom mark just to make sure. Same problem.
Again, I'm baffled. Anything thoughts?
03-11-2006, 09:16 AM
#2
Hi, smoke when coming to a stop after the car is warm is a pretty good sign of warn valve guides as you yourself point out. It doesn't *have* to be that - but that would be my vote. AFAIK there is not necessarily any danger at all in driving the car like this although you will burn more oil of course. I think a top end rebuild might be in your future - but it could be a ways off depending on how embarassing it gets at stoplights...
03-11-2006, 12:43 PM
#3
Nordschleife Master
Hiya
It doesn't sound all that bad , a little smoke now and then from a motor with 106k miles and no cat .
If it did not smoke at all ever , that would be odd .
" when its been at elevated rpm, say 3000rpm or so, for a decent time "
I guess thats under load , so its good and hot .
" I cannot mimic this by raising the rpm manually and then letting it drop to idle"
Its not under a load , so not so hot ? The cooling fan runs at the same speed if you are asking the motor for as much hp at 3k rpm as it can make or if you just crack the throtle open a little and let it spin 3k at min hp unloaded .
The oil thats geting out via the exhaust gets cooked by a very hot exhaust system and makes smoke ,
the smoke is allways made , but when the throtles open the smoke is a very small amount vs the amount of air passing out the tailpipe ?
Whats the inside of the exhaust pipe look like ?
It doesn't sound all that bad , a little smoke now and then from a motor with 106k miles and no cat .
If it did not smoke at all ever , that would be odd .
" when its been at elevated rpm, say 3000rpm or so, for a decent time "
I guess thats under load , so its good and hot .
" I cannot mimic this by raising the rpm manually and then letting it drop to idle"
Its not under a load , so not so hot ? The cooling fan runs at the same speed if you are asking the motor for as much hp at 3k rpm as it can make or if you just crack the throtle open a little and let it spin 3k at min hp unloaded .
The oil thats geting out via the exhaust gets cooked by a very hot exhaust system and makes smoke ,
the smoke is allways made , but when the throtles open the smoke is a very small amount vs the amount of air passing out the tailpipe ?
Whats the inside of the exhaust pipe look like ?
03-12-2006, 10:02 AM
#4
Burning Brakes
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yeah indy, actually I was considering that conclusion as well, I've been basing temp on that single sensor in the car, but that doesnt tell much for deviation around the engine. Especially when under load and not just revving the engine.
Inside of the exhaust, don't know right off. I tend to get a yellowish film onthe bumper from what I've read as meaning rich. I'll have to shine a light in there and check.
I'll drop in the thicker oil next weekend and maybe all will settle out. I have no problem with it puffing a bit now and then. Its not new. I was just hoping to get 20,000+ or so more miles before tearing it down.
Thanks for the replies guys.
Inside of the exhaust, don't know right off. I tend to get a yellowish film onthe bumper from what I've read as meaning rich. I'll have to shine a light in there and check.
I'll drop in the thicker oil next weekend and maybe all will settle out. I have no problem with it puffing a bit now and then. Its not new. I was just hoping to get 20,000+ or so more miles before tearing it down.
Thanks for the replies guys.
