White smoke diagnosis help requested !

A one NZ with a head gasket leak at 180K yeah it's possible likely probably not last for some reason it's been overheated unbeknownst to whoever which I kind of doubt because you'd smell it more than likely and then it would be quickly downhill from there.

 

You're either losing coolant (downhill) or losing oil (uphill) or both with those symptoms. Yet you say your oil and coolant levels haven't changed? And cars usually don't smoke when you're going down a mountain with little use of accelerator unless your brakes are failing... There's zero reason to blame it on a bad head gasket in a 2007 because they rarely have that problem. It's not water condensation either.

How's the gas mileage?

At this point only thing you can do is a thorough inspection of the underside of the car and engine compartment for anything that looks wrong, but other than something you think you're seeing in your rearview mirror you don't have anything wrong with your car.

Is it possible you or someone else did some really extreme off roading and this is just large amounts of light, near white colored dirt and debris that was packed into the underside of the car?

 

The good news is that you are paying close attention... The bad news is without dash warning lights or other symptoms its too soon to say... When I face situations like this the best way to handle it is spend a few hours cleaning every nook and cranny of the car while making a list of every minor thing that can be fixed so when you do figure out what this problem is it's the last thing that needs attention.

 

Cats only cool down on plugin hybrids and even then its not gonna create weird smoke... As for monitoring coolant level its not very easy on Gen2, but fill the reservoir up as full as possible so even just a tiny loss of coolant will be noticeable.

The only time I've had a problem like you're describing was when I put a rebuilt engine in my Subaru and didn't replace the radiator hoses and one of them failed and leaked onto the exhaust manifold... But in a Gen2 Prius I'm not seeing how the same thing could happen.

 

Always check the coolant level at the radiator itself. If you have any coolant system leak, the siphon to and from the reservoir will not work reliably. if at all.

The fact you're mentioning the coolant thermos, does that mean you've drained the engine coolant system recently? If you had air trapped there that subsequently freed itself, then you could have a low radiator and a subsequent failure of the overflow system.

 

Long downhills can fill up the hv battery and then engage engine braking with no fuel or ignition. Effectively a vacuum pump which can suck in oil from worn valve seals or rings. Then it burns off as a one time event.

 

Yes, I should have clarified that if checking fluid level at the radiator cap doesn't show a loss of coolant you can also try filling up the reservoir as full as possible so you can keep an eye on that as well.

 

I bet you could test what Hill said by putting it in B on one day downhill and putting it in neutral on the same downhill on another day.

 

Probably not a good idea. Just fill to the F mark on the tank. There needs to be headroom to allow for the expansion of hot coolant.

 

How did the experiment with using B versus using neutral at the bottom of a long downhill go?

 

Hello,

I have this problem. Steep, Long downhill runs, hot or cold weather, not as bad cold. At bottom of hill, at take off, large plume of whitish smoke, for half a block , then purged. The HV battery has to be full. I have tried the experiment, of putting it into neutral and coasting as much as possible, to not let HV battery fully charge. This seems to work. With little no no smoke, at the bottom at stop, and then takeoff. It doesn't throw codes. No leaks underneath at all. No water/coolant in oil, no oil in coolant. It does go through some oil. Yet I'm on top of it daily. 310,000 miles, runs great otherwise. I was thinking, piston rings. However valve job should be easier. Never had overheat issue. Hardly ever top off coolant in either reservoir, check it all the time. I frequently run in Vegas desert heat highway speed 75 at 115°. Rings and valves explain oil losses. However, never smokes in city, or if HV battery is not full.

 

When your battery is full the system does engine braking to save the brakes on a steep downhill. During this time the ignition and fuel is off. The engine then becomes a vacuum pump of sorts allowing oil to get past the bad rings and accumulate in the cylinder. At the bottom your engine starts (not just engine braking) and then burns off the oil in a white cloud.

In neutral you have no engine braking but you could overheat the friction brakes.

The engine needs to be rebuilt or replaced.

 

So then your smoke and your car and your tailpipe and all that around that area smells like oil after these events not glycol coolant... just saying You should readily smell the smell of the glycol or the oil burning like all the time It's like all over the back of the car not that you necessarily can see it on the rear bumper but maybe that too But the oil particulates are all underneath and around the tailpipe and hatch area etc not in the front of the car necessarily because you're going forward but you should definitely be able to smell the oil or glycol smell pretty much anytime you walk up near the back of the car It's a permanent smell that will stay until it's fixed generally something you don't forget if you've owned like old British Leyland cars like MG triumph Aston Martin etc you'll know the smell

 

Thanks RJ, I wasn't sure, my own brain thought rings only. I appreciate everyone who posts here. Now I can focus on Valves too. Just knowing there is vacuum and sucks the oil, this is why there is excessive oil loss on that downhill. With regular driving its about normal loss. Thanks for heads up.
I was staying off engine braking because I thought it might be harsher on rings. Will now be the go to on downhills. Thanks again

 

Tombukt2

Yes on the downhill event, when hv battery gets full, there is some excessive emissions, sometimes visible, but only after acceleration.
If you accelerate, while downhill, hv battery full, you could see some smoke. The smell, yes, I find if you keep the windows up, the fresh air intake on climate open. You can avoid, burning oil emissions. If you accelerate during this event with battery full. Then more emissions come out. More chances of smell infiltrating vehicle. Partially because there is some Cabin vents, on both sides of the car in rear wheel wells. This helps vent the cabin pressure. However I think it allows emissions in. The HYbrid battery cooler vent, exits the cabin vent, just behind the 12 volt battery in wheel well. It doesn't take much for these vents to open and close. Especially at higher speeds. the hv battery cooler vent has about 1 1/2 inches of space between the end of it, and rear wheel cabin vent. Which could allow emissions from hv battery cooler vent into cabin, as well as tailpipe emissions, again this only happens when Hv battery is full. This could be through normal city driving. Light smells. Or during a full Hv battery downhill event, where you get a lot of smell. I tried covering the 1 1/2 in space, between cooler vent, and cabin vent in wheel well. Didn't seem to help. If you open the windows, even a Lil bit the cabin air will open, the wheel well vents, and this allows emissions in to some degree. This is why I don't open windows during full Hv battery events. I also open the fresh air vent on climate. If you leave it on recirculate cabin air. During the event. It just reticulated emissions also. It's kind of like if you left your rear cabin open while driving, or not closed tightly, those tailpipe emissions come in.

Hope that helps