Overfilled gas tank, did I hurt it?

Not necessarily

 

The excess gas came back out the filler neck. Sounds like the expected operation, as the bladder surely can't over-expand due to the physical constraint of the tank itself?

 

it's not the bladder. the excess gas enters into the emmision charcoal cannister and destroys it.

there's no way of knowing except to wait for a trouble light. it's a complicated and expensive repair unfortunately

 

As bisco said, the risk is more to other components than to the bladder.

There may be a trouble light later, or not. You may later have problems with fuel nozzles shutting off way early, and being unable to pump any more than a fraction of a tank. That becomes more likely for people with a long habit of 'topping off', but it isn't inevitable after one single time.

So keep an eye on it for a while. If you notice any of those issues, you'll know what has happened, and if you don't ... go and sin no more.

 

Maybe just drive it for a while on the highway to burn off whatever liquid is in the canister? Not sure how long that would take if it is actually full of liquid, normally there is just the gas which is sticking to the charcoal, which would only be a tiny amount if it was all liquid. The purge valve would have to be open, but the Prius probably does that like any other car (as long as the motor is running).

 

Sometimes the system gets flooded beyond recovery, and repair is needed.

As long as that didn't happen, it pretty much takes care of itself without needing much attention from you.

 

The filters the hardware store guy mentioned is what normal metal gas tanks have to clean all the air inside the tank that is displaced when you fill up an empty tank. The bladder design eliminates the need for the filters because the collapsing of the bladder in the tank when it is empty means there's very litte air displaced inside the tank that needs to be filtered.

It was a great idea in theory when it came to designing a car that reduced air pollution in every possible way. But in practice, the design in cold weather meant the rubber bladder doesn't expand fast enough and you get gas puked out. Toyota discontinued this design for that reason, as well as for inaccurate gas gauge readings.

 

Just drive it til you go down a blip.

 

If the ABS or VSC lights come on, probably the circumference difference is too big. Might only happen at higher speeds.

If not, then the difference is small enough the ECU doesn't mind.

The idea of the bladder tank was to perform even better than a tank with only the normal EVAP and ORVR stuff, not to have a bladder instead of the EVAP and ORVR stuff. The bladder tank still has that stuff. That's the stuff that usually gets hosed when the tank gets overfilled.

 

The traction control in the VSC light and all that should be on directly or be flashing on and off trying to get to speed from the non-matching tires I just went through this 3 weeks ago

 

If two tires have slightly different circumference, the wheel speed readings will be different, and the difference will be larger (in MPH) the faster the car goes. Twice the difference at 60 MPH as at 30.

That's why, with a slight mismatch, sometimes you don't see any warning lights at low speeds, but only at higher speeds.

 

If the car "drives ok", then the tire diameters are close enough. The most likely problem would be if the sizes are too different, then the traction control would see a difference in wheel speeds from front to rear (usually at highway speeds). The ecu would flash the "slip" dash light while blipping the brakes and throttle to try and fix the perceived wheel spin.

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