Used car, sudden white exhaust that has sickening smell

Bought a used vehicle, 2 and 1/2 weeks later it is suddenly putting out white exhaust for a few minutes after starting up. The exhaust now smells sickening (to me) at all times, and must keep the windows up; I’ve noticed sneering from others in line at the drive through. I read online that this could be a gasket leak. I checked the oil and it looked clean, so I drove it back to the dealership to have them look at it. They called today to say that “checked the fluid levels” and that there is no evidence of a “consumption issue” at the moment, and suggested I drive it for a while longer and then have them check it again. It came with a 3 month / 4000 mile warranty, and I drive so little 3 months will pass by sooner.

What should I be considering?

Take it to a trusted mechanic and get their separate diagnostic?

I read that antifreeze mixing in the combustion produces white / sweet smelling exhaust… I suppose the exhaust has a sweet component to it.

I purchase my gasoline from the same name brand station in my family’s other two cars and neither have problems.

Assuming worst case all around, and it is leaking antifreeze into the combustion chamber… could the dealership be using any sort of laced antifreeze to prevent some drastic breakdown within the 3 month warranty period?

Suppose it runs as is for a year, and then breaks down, if it is leaking antifreeze into the combustion chamber… need a new engine?

I saw a reference somewhere that, if the seal is leaking, a compression test could be done to see how bad… can any shop do this? or is this a specialty work?

Look at the oil on the dipstick. Is it translucent, or does it have a milky appearance? If it’s milky and/or foamy, that’s a good sign of a head gasket leak.

Next, look at the radiator fluid (obviously, do this when the car has been sitting overnight so you don’t scald yourself). If it’s a nasty brown color, that’s also a good sign of a head gasket leak.

I strongly suspect from what you’ve said that there is a leak. It’s possible the dealership put some stop-leak into the engine to temporarily hide the problem, but it’s also possible that it’s just an old car and the head gasket crapped out on you.

I do suspect the dealership isn’t being entirely up front in their diagnosis - sometimes they will try and stall you off until the warranty runs out, hoping you don’t pursue it further.

There’s nothing stopping you from taking it to a good independent mechanic to see what’s wrong - if he says there’s a problem, then you can take it back to the dealership and say that you have evidence there is a problem and want it fixed under warranty.

Take it to an independent shop and have them document their findings.
Yes, the dealership could have put an additive in to try to hide the problem until the warranty expires.

You may not notice a significant loss in oil, as a little goes a long way. If the dealer can replicate the problem they should be responsible for the problem. Leave it overnight if necessary, and ask if they could check the valve guides.

Make, Model, year, mileage…??

Take it to another mechanic. You should hear the words “block test” and “pressure test.” It’ll be the best $200 you’ve ever spent.

Because there is a warranty involved, you should get them working on this soon.

If it does this every day at the first startup you might want to consider the following
If it’s not too much out of the way…why not drop it off one night after they have closed.
Park as close to the service desk as possible.
And the next morning…drop by 10 minutes after they unlock the doors.
This way you can insist that they wittness how it starts for you in the morning
and they cannot lie to you, with you right there.

I had a friend that had to go this route. He kept taking the car in and they were supposed to start it in the morning. Of course he was never there, so they just started it and said that it started just fine. Once he did it this way it was hard for them to claim that it started fine…with him standing right there.

Maybe then they will do a pressure test and block test.


Yeah, sure sounds like head gasket/antifreeze leak to me. I base this on having had one just like it.

Except the radiator on that old opened the radiator cap, and started it. Fuzz grew on the coolant, which is how he said to check it. Do it very cold, of course.



oil on the dipstick. Is it translucent, or does it have a milky appearance?
it is translucent, it looks clean

“block test” and "pressure test."
What will these tests reveal?
Can any repair shop perform these tests?

This way you can insist that they wittness how it starts for you in the morning
The service rep said they see the smoke and agreed the exhaust “smells off”, but will not do anything unless they see “consumption issue”, which after asking him to define what that is, he said that the antifreeze or engine oil levels must drop. Essentially all they did was check the level of the engine oil and antifreeze in the radiator and then called me to come pick it up.

ask if they could check the valve guides
I will ask when I take it back later. I plan on taking the vehicle to a trusted repair shop, is this something I should ask them to look at too?

It’s possible the dealership put some stop-leak into the engine to temporarily hide the problem
Would this be evident somewhere on the outside of the engine? or in the color of the radiator fluid/antifreeze?

>oil on the dipstick. Is it translucent, or does it have a milky appearance? it is translucent, it looks clean

What about the second check?

The service rep said they see the smoke and agreed the exhaust "smells off", but will not do anything unless they see "consumption issue",

Yeah, my BS detector is going off at this point. They know there’s a problem and are trying to stall it past the warranty expiration date.

Block test and cooling system pressure test will reveal a blown head gasket.

I agree with the other guys

This car dealer sounds pretty shady to me

They’re obviously trying to make it past the 3 months

Take the car to another shop. Have that shop perform the tests that the other guys mentioned.

Take those printed test results and the invoice to the jokers that sold you the car and tell them they’d better make it right. Tell them you’re not going to let them jerk you around until the 3 months are over.

I suspect the boss of that used car dealer puts his mechanics under tremendous pressure to “fix” all the cars as cheaply and quickly as possible, so that they can sell them and get them off the lot. That way, they’ll have space for the next batch

I agree that the dealership is dragging their feet…hoping that you’ll just go away, or the warranty runs out.


Get caught with a smoking vehicle were I live and you will be required to repair it or scrap the vehicle. Emission control compliance enforcement won’t care when you bought the vehicle or about warranty difficulties, you are given a limited amout of time to get it repaired.

Go back and tell them smoking is unacceptable and you want it repaired.

Got the car back after work yesterday. The invoice (no charge) says “UNABLE TO DULICATE AT THIS TIME”. I asked the service rep about him telling me on the phone they had seen the symptoms I had described and he denied it, says he only said “the technician found moisture in the exhaust”. I don’t know how they could miss a white cloud that is almost the same size as the vehicle before it begins to dissipate (when it is not windy outside).

The vehicle now does not emit white smoke from the exhaust, and the exhaust smells normal. I suspect they put more stop-leak stuff in it. My plan is to take it to an independent shop and have the radiator fluid replaced. IF the problem is radiator fluid leaking through head gasket into the combustion chambers, my thought is that this should speed up the reappearance of the white smelly exhaust. Once the symptoms reappear, I will have the same repair shop confirm the severity of the symptoms, perform a diagnostic (coolant system compression test) and provide me with their findings on letterhead, and receipt for their work. I am not sure I understand what a “block test” is, but I will request that too and see what they say. Then, take it back to the dealership and do what shadowfax suggested earlier in this thread, to start it up in front of them at their facility.

Am I missing something?

Suppose I do let it sit overnight at the dealership and they recognize the vehicle before I get there. Supposing they are daring enough, would it be possible for them to open the hood from the outside of the car and inject more stop-leak before I arrive?

Should I have a second independent diagnosis? or is one independent diagnosis enough?

My cursory understanding of the laws in my state, that an AS-IS used car sale does not preclude an expectation for a road safe and major defect free vehicle. If they refuse to repair the problem, what sort of lawyer should I be calling? is there a legal specialty for the automotive industry? – in my imagination I will take it in to their service center a second and third time and they will ignore any independent findings, the three months will be up, I will have the repair done elsewhere at my expense, then sue for the cost of the repairs (provided a lawyer says I have a case). The repair costs will probably be on the high side for an eight cylinder engine, but still low enough that my case would go to small claims court. Am I being irrational?

Yeah, they probably put more stopleak in there. And the more they do that, the more likely they’ll screw up more in the engine than is wrong now, because stopleak can plug up small passages, and then you’re really in a mess.

We (on this forum) tend to recommend stopleak only to the person who wants to get a few more months out of the engine before they scrap the car and get something else, for that reason.

Were I you, I’d be getting an attorney involved at this point, if I planned to get one involved at all. The more that dealership has access to your car and thinks they might get away with pulling something, the more they’re going to mess it up.

That said, I’m not entirely sure that you’ll get anything out of legal action – Dealerships like that tend to skip town in the middle of the night, only to reopen a few days later “under new management” and without any of the obligations they committed themselves to previously.

In short, I suspect you have now learned a very expensive lesson - do not buy cars from crap-hole little dealerships like that, because most of them are out to screw you 6 ways from Sunday.

I remember as a college student shopping for my first used car walking onto a lot like that, and watching as the mechanic, with absolutely no sense of shame whatsoever, poured sawdust into oil that was going into a transmission (which makes it nice and smooth and quiet just long enough to get it off the lot and into some unsuspecting rube’s hands,). I hightailed it out of there and never set foot on lots like that again.

Actually this is a well established dealer of new luxury cars thats been there 20 years or more. The used car that I bought was from someone who traded it in on their purchase of one of their new luxury cars. The car I bought is not the same manufacturer as the luxury cars they sell, not that that matters.

In that case, yeah, lawyer up.

“The car I bought is not the same manufacturer as the luxury cars they sell, not that that matters.”

Unfortunately, new car dealers like to spend next to nothing on cars they take in on trade . . . especially if it’s a brand they don’t sell

They want to flip it and wash their hands of it as fast as possible

It’s a rough business . . . and not always ethical

Start looking for a lawyer

It’s pretty clear to me, as well as the other guys, that this dealer means to wash their hands of you and your car

The next person they should hear from is your lawyer. Have him start sending correspondence, on his letterhead