Smoking Exhaust

[altezza_man]

has anyone else had problems with smoke coming out the exhaust after cruising down a big hill? it typically happens after backing off the accelerator while going down hill and then replanting the foot on the pedal and there's a big cloud of smoke that comes out. any thoughts?

[rig-pig]

just cause its so cold outside m8 just condensation

[DJ Wozza]

I'd agree with the above, but what is your oil consumption like & mileage ?

[is300_dino]

just cause its so cold outside m8 just condensation

it cant be that cold in new zealand though can it when australia been having heat waves?? tez_man you could always try booting it down the hill before you get to the bottom then there wont be no smoke when you boot it on the flats lol.

also how big is your exhaust as with going down the hill it maybe containing exhaust gases and then expelling them when it can ie. when it goes flat and you push all the excess gases out when you get going again~~????

hope that makes sense to ya, but im probably completely wrong :)

[Steviewevie]

just cause its so cold outside m8 just condensation

it cant be that cold in new zealand though can it when australia been having heat waves??

Lol yeah it's summer in New Zealand at the moment.

[is300_dino]

just cause its so cold outside m8 just condensation

it cant be that cold in new zealand though can it when australia been having heat waves??

Lol yeah it's summer in New Zealand at the moment.

yeah its alright for some it must be our turn for a heat wave soon ( will next week do for everyone :) )

[rig-pig]

a well that's the condensation theory out the window then.

i would go with wozza mileage and oil consumption

[jeffrosie]

Most probably Valve guides

[MacRS200]

Classic symptom of worn piston rings/bores, oil gets sucked up the bores on the overrun and then burns off when you accelerate.

Worn valve guides/stem seals are usually a puff of smoke when you first start up.

[ormi]

i agree with the above^^^^^^^^^^^^

[altezza_man]

yup definitely summer over here! jus got a standard exhaust so i thought it might be something like above with the seals as i had a GT starlet before this that had a similar problem. its done about 88K miles. its going through a bit of oil lately but i had it serviced 10000 miles ago and they changed the oil over and i just topped it up the other day. are piston rings/bores expensive?

[DJ Wozza]

It's an engine out rebuild really mate. The mechanic needs the engine apart to see what is worn/needs replacing.

[rig-pig]

find out what oil went in, the likes of Mobil 1 fully synthetic is v thin oil try putting in a 10/40 oil a bit thicker and see how it goes b4 engine out job

[altezza_man]

so would it be better to have the engine reconditioned or should i maybe look around for a new one?

[MacRS200]

First move is to do a compression test. If compression is low squirt a bit of oil though the spark plug hole, should be possible with an oil can with a long spout and a torch. Test again, if compression gets higher you have a problem with bore/rings.

IIRC compression ratio is 11.5:1 so you should get at least 10.5 bar on the compression tester.

As for recon or new, if you can get a new engine go for it. Personally I would go for rebuild of my own engine ahead of buying any second hand lump. At least you know what you've got to start with.

Apart from the smoke on the over run is the car running OK, if so I would say "don't worry be happy" and see how it develops.

ps. As rig-pig said - what oil are you using, as an engine gets older bits wear and oil will get through the bigger spaces so you could try a thicker oil.

Edited February 9, 2009 by MacRS200

[altezza_man]

I agree with the rebuild thoughts - i dont see the point of replacing it with an engine that could encounter the same problems! do automotive stores sell compression testers? The car has been running fine its just the smoke on the overrun that has me a bit worried - any recommendations on a good thick oil?

[MacRS200]

I agree with the rebuild thoughts - i dont see the point of replacing it with an engine that could encounter the same problems! do automotive stores sell compression testers? The car has been running fine its just the smoke on the overrun that has me a bit worried - any recommendations on a good thick oil?

Gunsons do a compression tester that is relatively cheap, don't know if you can get them down under.

What oil are you using at the moment?

[k33rjd]

the symptoms you have told us sounds more like valve stem seals, as macrs200 has said you could do a compression test, but if the compression doesn't improve with the small amount of oil in the cylinder then theyre is a fault with the valves. altough personally i dont think this will highlight your problem.

what you need to do is check the stems of the valves for oil contamination- i.e. the oil is coming by the valve stem seal and traveling down the stem, then being drawn into the engine. a compression test wont help identify this. it may be possible to remove the inlet manifold and have a look to see if there is any oil sitting on the valves that are closed.

i wouldnt recommend using thicker oil either. the specified oil is used due to the oil clearances in the bearings etc. and as youve said you have no other faults but the smoke on overun. sort the problem dont mask it.

[MacRS200]

the symptoms you have told us sounds more like valve stem seals, as macrs200 has said you could do a compression test, but if the compression doesn't improve with the small amount of oil in the cylinder then they're is a fault with the valves. although personally i don't think this will highlight your problem.

Would disagree with valve guide seals being the most likely cause, there would be smoke on start up. The oil weeps past the seals when the engine is stopped and collects on the seats or passes into the cylinder. No mention of that in the following.

has anyone else had problems with smoke coming out the exhaust after cruising down a big hill? it typically happens after backing off the accelerator while going down hill and then replanting the foot on the pedal and there's a big cloud of smoke that comes out. any thoughts?

With worn bores/rings, as I said before, the oil gets sucked up the bores by the vacuum on overrun and then burns off giving smoke when you accelerate again. The above is a classic symptom of this. For a "big clouds" worth of oil to get past the seals and then through the valve guides going down a hill they would have to be seriously knackered.

i would recommend using thicker oil either. the specified oil is used due to the oil clearances in the bearings etc. and as you've said you have no other faults but the smoke on overrun. sort the problem don't mask it.

The oil is indeed specified to take into account clearances when the engine is new, as engines get older the bearing clearances increase and the oil will pass through bearings faster than it would in a new engine. Using a slightly thicker oil won't do any harm, in fact it will actually help keep the oil pressure up and improve the pressure in the plain bearings helping reduce wear.

[Gord]

has anyone else had problems with smoke coming out the exhaust after cruising down a big hill? it typically happens after backing off the accelerator while going down hill and then replanting the foot on the pedal and there's a big cloud of smoke that comes out. any thoughts?

How many miles your car done mate and how old is the car

[altezza_man]

Car has done 90K miles or 150K kms. I had a chat to my local mechanic yesterday and are going to get them to check it out when i take it in for its warrant of fitness. it definitely sounds like it is more a worn bores/rings problem - what sort of work is involved in fixing this? is there any work the mechanic can do at the same time to add more power?