Engapol

I have a 2001 C320 with around 150,000kms on it and lately (last few months) the car has puffed out a bit of whitish smoke sometimes when I start it in the morning cold (and occasionally it does it during the day after I've been driving around and I've left the engine off for a few hours).

I live in New Zealand so the climate is very mild, I'll begin observing the exhaust on startup to see if I can get a clue but I'm still not sure what's causing it. It's not 'fluffy' and thick, it's wispy and definitely white. If there's any tinge of blue in it, it's not very obvious. It smells like regular exhaust except a bit stronger, like what you would get in a busy underground carpark. From inside the car, it looks like the smokes being pumped out for a few seconds then stops and quickly dissipates if I'm in the open, and it doesn't happen when I'm driving.

The computer hasn't whined about low coolant levels and upon visual inspection it's fine, despite not being topped up for quite a while. Nor has it been overheating, or running rough. The cluster also says the oil level is fine. I don't think it's the head gaskets since it's running smoothly and the smoke only appears on startup. I'm tempted to take it to a shop but could this just be condensation? (I'm not inclined to believe that since it's a recent phenomenon)

Benzomatic76

I think white smoke has something to do with the engine burning oil.

Cruel-Merc

How does it smell?!

Engapol

I finally got someone to start it while I stood by the exhaust, it's definitely some kind of oil burning.

Cruel-Merc

If the smoke dissipates shortly after leaving the tailpipe, this means it's actually steam and signifies a blown head gasket. This is bad. If the cloud isn't too bad and doesn't dissipate, then you could be burning oil. Depending where the leak is, this can be very bad or not terribly bad.

Engapol

I don't think so, it doesn't have any of the symptoms that usually accompany a blown head gasket. No milky oil, no smoke while driving, no loss of coolant and no overheating.

Glyn M Ruck

Get some indicator to check for combustion gasses in the coolant.

It sounds like steam to me. White and dissipates. Oil smoke is blue & contains particulates which will suck onto the back of the car. Overfueling is dark brown to black.

It might be normal.

What is coolant consumption?
What is typical oil consumption?

Does it clear on closed loop (non enriched) fully warmed up running?

Engapol

Suck onto the back? You mean there would be dusty streaks up the rear? It doesn't even need to warm up to clear, just a puff for a few seconds at the most when the engine comes to life.

Coolant has stayed normal, I've only had to give it a small top up once this year.

In DYNO mode the oil level is showing 7.1L or 7.5 quarts, my last oil change was around 6000km ago and I haven't been really monitoring it. I'm going on a roadtrip tomorrow though and I'll see if there's any drop.

Glyn M Ruck

If you are burning a lot of oil you will get black oil muck building up on the tail section of the car. Sounds as though your oil consumption is normal or you would be topping it up frequently between services.

This sounds like normal steam from combustion at cold ctart to me. Just monitor it.

Engapol

The rear is spotlessly clean, even though it's been a while since a wash

But steam would theoretically be odourless right? This stuff isn't.

Glyn M Ruck

The steam won't be odourless because it is polluted with combustion by-products.

Engapol

OK just finished a long drive and some observations:

The amount of smoke produced seems proportional to the amount of driving it's done, prior to being turned off and cooled down, e.g a hot restart won't produce smoke. And this is all happening in a New Zealand summer so it isn't exactly cold.

If I sit at a particular speed for a while i.e cruise at 80kph and then suddenly push it hard to 110kph then it belches out smoke, other than that everything is normal.

Coolant normal, will check oil level via console. I'm thinking it's something to do with the valve seals being worn, since the symptoms are pretty similar to what I'm getting now, I'll take it back to an indy or the dealer as soon as I get back home.

Glyn M Ruck

What colour is the smoke when you floor it at 80km/h. Are you sure it's not overfueling = black brown smoke??

Another possibility. Are you loosing brake fluid? It should run out pretty quickly. There is a possibility you have a brake booster leak. Does not happen very often.

Engapol

It's definitely not burning rich, just white, and if I'm driving on a non-straight road where my speed varies then I can floor it without problems. Brake fluid is normal.

Glyn M Ruck

I'm running out of ideas. It must be either oil or coolant then. Get an indicator strip & check coolant for combustion gas.

If you run the car down a hill against compression & then floor it do you get a cloud of smoke. If so it could be a sign of worn valve stem seals or rings.

Check coolant as advised. Watch oil consumption.

Engapol

That's what I'm beginning to think as well.

Glyn M Ruck

If it becomes a problem you can have a leak down test performed to see where the problem lies. Also make sure that all the cars breather & EGR pipework is clean with no blockges including the EGR valve.

KSKarl

Right, Glyn, reading back through the thread sounds like an aging crankcase vent system drawing in a little oil.

Engapol

Alright the problem is getting worse now, a while ago it only produced smoke on startup but now when I floor it up a hill it makes clouds of white smoke. I also spent around 1 hour on a motorway doing 100kph with cruise control and when I got back into the city, when I pulled away fast from the first traffic lights it belched out smoke. I'm taking it to the dealer tomorrow.

It feels like the oil sort of builds up as I drive and gets burnt off when the engine gets stressed, e.g after I makes lots of smoke then it's clear for quite a while.

Engapol

OK I took it to the dealer and they said it was 'normal' for an old car and it was just carbon buildup, apparently nothing was wrong with the engine. I was a bit unsure since the problem felt much more serious than that but I went along with it anyway. They gave me fuel additive for two tanks of fuel and despite running the tank empty twice in one week of 'spirited' driving as recommended, the problem suddenly got worse. I also got a routine oil and filter change while the car was there (would've done it myself but they only charged marginally more than what I would've had to pay for two containers of 0w-40)

The check engine light went on on the motorway, I believe for the first time in the car's history and it was accompanied soon after by very rough idling and seperately, a huge cloud of grayish/black smoke for a few seconds out the exhaust. The roughness went away when the car moved off and the new colour of smoke didn't persist, though the check engine light is still on. This is approximately a week after taking it to the dealer.

I'm taking it back to them, depending on what they say and how exorbitant the charges are gonna be, I'm taking it to a BMW & MB Indy nearby. I'm sick of continually having the car mis-diagnosed.

Engapol

The dealer is now saying it's worn piston rings which are causing the suspected misfires, and only a prohibitively expensive rebuild or replacement engine can fix it. Apparently carbon had built up around the rings and gave the impression that it was OK until the fuel additive removed it all, however could it still be worn valve stem seals which led to fouling of the spark plugs?

I'm still not sure since I'm not getting any constant smoking from the exhaust while driving, any smoke is a brief belch and only in conditions stated before. I can't say the 'misfire' is severe, I just went for a half hour city drive and all I got was the occasional slight vibration from the engine while idling (which has always been there AFAIK). I'm just surprised since it's a touch over 100,000 miles and the M112 is supposedly a very tough engine.