the gas bladder: exposed!

[Patrick Wong]

Originally Posted by ekpolk

But more on point, if they were able to make the TCH as clean as it is, with no bladder, why on earth does the Prius really need this Rube Goldberg regurgitating fuel tank???

Recall that the US Prius fuel bladder system was first put into production in 2000, for the 2001 model year. When did TCH first start production - 2007?

Note that the TCH fuel system is pretty complex also, with a special pump to deal with HC vapors. Highlander Hybrid has a similar system although that vehicle is SULEV rated only, not AT-PZEV.

My guess is that 3G Prius will have a fuel system that is similar to TCH and HiHy.

[ekpolk]

Originally Posted by Patrick Wong

Recall that the US Prius fuel bladder system was first put into production in 2000, for the 2001 model year. When did TCH first start production - 2007?

Note that the TCH fuel system is pretty complex also, with a special pump to deal with HC vapors. Highlander Hybrid has a similar system although that vehicle is SULEV rated only, not AT-PZEV.

My guess is that 3G Prius will have a fuel system that is similar to TCH and HiHy.

Patrick:

I'm right with you on all of this. Sure, absolutely yes, the Gen-2 Prius predates the TCH by at least three years. But even accounting for this, you've gotta suspect that containing vapors isn't such rocket science that they couldn't have achieved goals without just a hard tank. The bladder is a nifty solution to the problem, but at least in my calculation, the potential issues outweigh the benefits, albeit only slightly, especially when again, it's pretty clear that they could have solved the problem without a bladder. Automotive engineers should be made to recite some mantra centered around the old, but ever-serviceable, K.I.S.S. rule, every day, without fail!

Yeah, I'd bet a paycheck or two that the US-G3 Prius will get an improved variant of the TCH's "hard" tank, and the bladder, perhaps the most problematic aspect of this otherwise SUPERB car, will be history.

Patrick, thank you for your outstanding, thoughtful input to this site; have a great weekend.

[galaxee]

well, by purchasing our cars we indirectly paid for the r&d for the sealed metal tank. no sense in changing over the entire system mid-design, given all that needs to be wired and programmed in. i fully expect to see the sealed metal tank design make it to the next gen.

at any rate, who knows the situation that caused them to throw the bladder in there as opposed to designing something else. the bladder is not a new concept, maybe they intended to expound on that and just failed to do it conveniently for the end user.

[freshspeedo]

Sorry for the question.

Basically when you are filling up when the pump shuts off then the fuelling process is done.

The other day it clicked and I added around3 litres after that point.
Does that mean I overfilled it then???

Don't want to cost me big time for being stupid.

[David Beale]

If you didn't see fuel in the filler tube when you were done filling, it's likely you didn't cause a problem. If you read through the whole thread (which takes a long time now), those who caused a problem did so almost immediately. If you have no lights on, you're ok.

I've overfilled three times now (liquid fuel in filler tube, shaking car to get all the bubbles out) with no problem. If you do this, you will have to worry about the fuel expanding. In the ground it's at about 10C. If the air temp is above that, the fuel will expand. If you put the cap on the expanding fuel has nowhere to go, so it is forced past the vapour control system into the gap between the bladder and the metal tank, in the process possibly forcing hoses off their fittings.
So if you see fuel in the filler tube, leave the cap on loose, expect a light to come on eventually (because the cap is not on tight), and drive to burn the excess fuel. If you just park it with the cap on loose, the fuel will probably expand and slowly seep out, without creating enough pressure to damage the system. If a light does come on, it should go off after a number of cycles of running the car, once you have retightened the cap. Just check that you can no longer see fuel in the tube, and tighten the cap.

[john_dough]

David---I've read through this entire thread and, until I read your post, didn't understand why some fuel between the bladder and hard tanks is a bad thing--it's because, in doing this, a fitting may come loose due to excessive pressure. Thanks.

[galaxee]

update complete. all of my posted pictures are now safe from server changes and such. but if photobucket ever goes down and i have to do this all again i will be pissed.

[galaxee]

john: gas between the bladder and the tank is an evaporative emissions concern, and also an indicator that the tank system is damaged somehow.

fresh: overfills happen here and there, but if there's a serious problem you won't likely make it out of the parking lot without a warning light.

[David Beale]

Originally Posted by john_dough

David---I've read through this entire thread and, until I read your post, didn't understand why some fuel between the bladder and hard tanks is a bad thing--it's because, in doing this, a fitting may come loose due to excessive pressure. Thanks.

As Galaxee said, it's an evaporative emissions issue. It causes a "mil" to be entered and the check engine light to be lit. You will not pass inspection. Fuel there -may- also cause damage to the bladder eventually. It's designed to be dry. The fuel can also dissolve glues etc on the equipment that resides in that space (evap system).

It may not take much pressure to force fuel into that space, once you have soaked the canister, so leaving the filler cap loose ensures that -no- pressure is applied.

Please note that I -DO NOT- recommend overfilling. It's happened to me due to filler nossles not shutting off. I -CAN- get more than 100 km further range by filling past the shut-off, but when I do this I do so very carefully and conservatively. So far I haven't made the mistake of filling so far I can see fuel in the filler tube. If I do, I will leave the filler cap loose until I have driven at least 5 km, checked that the level is down below sight, and only then tighten the filler cap.

As you can see from the photos, there are no "user replaceable parts" inside. The "new tank" fix is one I would prefer to avoid. Though even that is not a bank breaking fix (depending on your banks state ).