Exhaust with white smoke, looking for fire

No please don't put any of that in the Prius even some of this latest stuff in the blue bottle with green on the label and all that but they've come to my shop with that stuff. And well personally I don't have any part of it If you want to pour that in your stuff that's your business and you've got possible radiator clogging that stuff has to flow all through your cooling system all the pumps on our cars and all that business you're going to have the sealant crap floating around I don't think so on your stuff yet that's your business but over here no we're not going to be having any of that You just making a lot more nonsense for me to clean up and I'm charging you for it so you know let's not be doing that That's just for the let's see factor maybe possibly it might yeah forget all that You know might let you get the car into somebody else's hands real quick so it can fail tomorrow or the next day but you know I don't want to be dealing with any of that.

 

I have VRP in my car now and it did not cause any sort of smoke. 139K miles (something like that, too lazy to walk out to the car to check.) I don't believe that anybody claims that it cleans the top of the piston. Oil isn't really supposed to be in there, and if it is it isn't going to have much time to work before it is incinerated.

The tesslong front and side borescope for around $40 on Amazon gives very nice pictures. But you need a phone with a USB C connector, because it does not work well through a USB-C to USB-micro adapter. It looks forward or to the side, but not backwards.

DO NOT USE A HEAD GASKET SEALER. Well, maybe OK if you intend to junk the car very soon because it is developing some other intractable problem. The sealers will gunk up everything in the cooling system, won't hold forever, and will eventually come back to bite you in the butt.

Try testing the pressure in the cylinders. It is harder to screw up that connection, since it screws in. If you pressurize the one you think is a problem and the fluid rises or bubbles in the radiator neck, then there is definitely a path between the two. Probably a blown head gasket. Possibly something worse.

Did the car ever overheat or get low on coolant or oil? Failed head gaskets are not very common in this vehicle. Unlike the 3rd generation, where they are a very common problem.

 

So you changed the oil and it started smoking? But that could be the reason.

 

What condition is the oil in now?
Сolor?
Viscosity?

If the oil really started to wash out slag from the engine, then this slag will settle in the crankcase at the bottom of the cover.

The oil pump, catching all the muck from the bottom, will quickly become clogged.

Without lubrication, the engine will come to an end.

 

Is that not also consistent with a wide variety of valve problems? Possibly even timing belt/camshaft issues if they prevent both valves from being closed at the same time. I'm sure they put the piston at TDC, and equally sure they didn't scope inside to verify that the valves were actually in the correct positions. There are ways to tell where the air is going. For instance, listening to it. If the intake valve isn't closed when it should be, and a problem cylinder is kept pressurized, at least some of that air should come back out the throttle body. And so forth.

Is the right dial really psi or is it % loss? Leaking 10% is normal. Leaking 40 psi to get to 10 psi would be terrible, that's an 80% loss. A car would run like crap with a compression issue like that, but that was not the case in the original post, just a little smoke.

What did the dials read on 1 and 3?

 

Maddox? That's a Harbor Freight tool.

Cylinder Leak-Down Tester

It is a little surprising to find it in use at an actual mechanic's shop.

 

Your burning oil plain and simple. The rings wear out, a common gen2 problem. It needs a rebuild or you risking the very expensive cats. Your shop diagnosed it the first time.

Sometimes logic is difficult and clues are scarce. Not in this case. No oil or additive will fix it.

 

Good to know RE: seals -- I have oil consumption and occasional smoky starts, but no coolant loss. I might be lying to myself, but it's been like this for 13E3 miles, so :shrug:

IDK about the "overwhelm" characterization -- cold catalytic converters don't do very much.

 

Perhaps the OP is overthinking this. If somebody tells you "my car smokes only on startup" it is almost invariably a problem with the valve seals leaking. I don't know if the Gen 2 Prius is one of those motors where it is relatively easy to replace these from the top, or if it requires the head to come off. I have seen references here and there on this site to bad valve seals, but not a procedure for replacing them.

Hmm, on the other hand:

Leaking valve seals often result in poor leak down tests. The OP is not seeing that, at least not yet. Or maybe the engine was too warm at the time of the test for the leak to appear?

Some people claim that if the drain channels from the head are at all blocked that it can result in oil leakage through the valve seals. Not sure I believe that. Certainly not worth pulling the valve cover to find out. Maybe try Valvoline Restore and Protect on the next oil change. If there is gunk in those channels that will probably clean it out, and if there isn't, it won't hurt anything.

 

Valve seals cause the cold start puff; rings cause the major oil consumption which is slower but continuous.

 

Odd that in each there are two dark valves and two light ones. Is that normal for a Prius? Are the same ones dark in each cylinder (both intake or exhaust)? Looks like the larger valves are always darker, whichever one those are. I didn't see any drops of oil. Some parts are more reflective than others, but in borescope pictures that is often due to slight changes in the angle of the camera or light, rather than a little bit of oil.

In a picture search found similar shading here:

Rebuilt the Engine; Won't Go Now??? | PriusChat

but that engine has bent valves. Here is another with the same shading pattern:



I have never rebuilt an engine, naively would have expected all the valves to look the same from the inside of the cylinder.

 

Lean mixture, greater heating of the exhaust valve. Therefore it is light shade.

 

The exhaust valves are always hotter so any deposits will bake on. That's why they are different color. The intakes stay about the same temperature as the rest of the combustion chamber

Leakdown tests will not find stuck oil control rings. The compression rings will seal just fine until they get carboned up & seize.

The same is true for valve stem seals. Take the seals out and throw them away. The engine will run just fine, other than sucking down quarts of oil.

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