Exhaust with white smoke, looking for fire

Prius Gen2 with 211k miles is almost a youth. Is the catalytic converter original?
It is better to check the coolant leak into the cylinders with a borescope in the morning before starting the car through the spark plug wells.

 

White smoke when cold is typical in the winter, if you are somewhere cold. Head gasket failure smokes all the time. Your oil consumption is well within normal for a car that old. You have done all the maintenance stuff, maybe the air filter could be replaced but that would not cause shuddering. Just drive it and relax. And PLEASE don't take it to a dealer, you will regret it.

 

Probably nothing wrong with your car I would just drive it I don't know where you're located We shouldn't have much into it so I wouldn't be looking for trouble getting 45 miles to the gallon on occasional shutter and stutter has anybody looked at any of the freeze frame data for this car That's a good place to start sounds like you don't need a whole lot of work looks like you're up on oil changes transmission stuff brakes brake actuator comes to mind around this mileage stuff like that The car's general condition is good to better I wouldn't worry about a thing It doesn't sound like it's anything that's going to leave you stranded If you're burning coolant and or oil standing behind the car while the smoking is happening should produce the smell of the substance that's burning coolant is almost unmistakable and oil oil that should be too You don't forget it once you smell it white smoke coming out of the back of a generation 2 Prius with this kind of mileage in the winter I would say is not really problematic You're not making a cloud that people can't see through.

 

Keep an eye on fluid levels and see how things progress.

First sign of a head gasket coolant leak is (minor) engine misfire on cold start. Then it goes to noticing coolant loss, white tailpipe smoke, overheating, etc.

A major fuel injector fault can cause white smoke but it's also going to have misfires, bad mpg, etc.

Since I assume it's not "normal" water vapor, then the only thing left is oil. Either a (serious) piston ring problem or PCV is pulling (more than normal) oil.

You could pull and check the plugs for oil fouling. If available use a videoscope to look in the cylinders for oil pooling on a piston.

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This is like being a little pregnant.

A positive is definitive; a negative is not. A borescope with a pressurized coolant system is needed if you get a negative.

No cold morning water vapor there.

Your best hope is excessive oil burning is causing the white smoke. However the reason everyone steals gen2 cats is they are expensive and are very effective in eliminating hydrocarbon emissions at the tailpipe without using an egr system.

If it is burnt oil you are seeing it might be valve seals dumping oil into the cylinders overnight with a cold start burning so much it overwhelms the cats. Oil burning from rings is unlikely to get past the cats.

 

Are you sure the smoke is white? Worn valve seals drip oil into the cylinder(s) when the car is off, and when it is turned back on it smokes briefly. Typically that is a little grey or blue, but maybe the super powerful 2nd generation cat takes the color out of it? On many cars there are tricks for putting new seals on the valves without having to pull the head. If this is really the problem here, and there is no such trick for this car, then it might as well be a blown head gasket, because the head would then have to come off either way.

Do you have a borescope? Looking into the cylinders after the car has sat overnight while the coolant system is under pressure should be informative. Either you will see oil in there before pressure is applied, or you will see coolant dripping in after it is. Also the state of the spark plugs is of interest.

It actually does get cold enough in SoCal to see white condensation from the exhaust. But only just, more of a wisp than a cloud, and only on particularly cold morrnings. Of which we have fewer and fewer each year.

 

In the summer my Gen2 smoked blue smoke... after I used dimethyl sulfoxide to decarbonize the engine system.

In addition to the blue smoke, there was a characteristic smell of garlic.

It is strange that the author of the topic does not mention the smell of exhaust smoke, he could explain a lot.

This is roughly how the smoke came out of the exhaust

Smoke by MAX2 posted Feb 19, 2025 at 11:03 AM

 

This could be a consequence of Covid. I also lost the ability to taste and smell for about a year and a half.

 

Sounds like a head gasket. If you are using an antifreeze/water mix the exhaust should smell sweet but the pressure test is probably more accurate.

 

Where is this Max that shipping container and whatnot You out in Oregon?

 

I pressure test the system - 15psi is plenty. Often leave it pressurized overnight. Pull the plugs and look in the cylinders (lots of videoscopes on amazon).

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And he said he can't get any pressure at all like pump up and the gauge just goes down I guess like immediately while he's watching it with something like that going on I would think with the spark plugs out and your friend pumping on the pump and you holding a tube in each cylinder hole one by one listening with your ear in each cylinder hole through the spark plug You would almost hear that much air escaping or if you blow through it with your air compressor set at 8 for 10 PSI and you're 100 ft from the compressor with your air hose length You should be able to hear that air running out of wherever it's running out of at that kind of pressure I would think That's a pretty serious gap. Makes me wonder if that's really a head gasket or if you're pushing air past the hose fitting or something of course I haven't spent a lot of time listening and messing with head gaskets like this but that seems like an awful lot of pressure vanishing before it can even start to build up It's like you're blowing your air right into the atmosphere That's surely is one hell of a head gasket leak for a one NZ engine not to say it can't be but that's a good one

 

Damaged cooling system testers are pretty common if they are rentals from the car parts places. People tend to not be so careful with other's tools.

However, when the cooling system is pressurized:

which I think means the amount of smoke increases with pressure. That is almost certainly a blown head gasket or, less likely, a crack in the block or head to the water jacket. I guess it doesn't smoke all the time because when it heats up something expands enough to choke off the leak, and here the car is running cold.

 

It doesn't seem to me like that's a lot of cleaning going on by steam that actually looks pretty reasonable for the top of a reasonable mileage one NZ if I'm not mistaken. What you want to do is get the camera to look back up at the gasket surface so you can see the water droplets if they're there especially with pressure pumped up even with it out pumped up early in the morning non-started nothing plugs already out waterfall You should see droplets forming where the gasket mating surfaces are for the head gasket which is down in the boar and looking back up lots of cameras can do this now they're not that expensive I wouldn't imagine it AutoZone would have that feature but there you go but you got white smoke and you're losing some coolant and all this and that so it's a pretty good guess that you've got some head gasket seepage going on how much don't know probably can keep driving for a good while You're doing all this work to determine whether you're going to fix it if the hybrid battery is good and all these other parameters are met screw that I just keep driving it until the smoke becomes well dangerous like people can't see and if you're in California the vehicle enforcement people tell you hey man you got to do something about that Yes I sure do thank you that might be another year or two Just saying