P0446 may be caused by hose on top of trank
10-28-13, 02:17 PM
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P0446 may be caused by hose on top of tank
I've done quite a bit of reading about CEL P0446 on 1999 RX300 (2WD), in this forum and elsewhere, so I think my next question is new.
In looking at the large hose off the vent control valve (at the charcoal canister), I read that one driver had found his hose clogged by dirt dobbers. So to test, I just cleaned it off and blew into it (lung power). I heard air leaking out "somewhere", and with the help of a neighbor, it appears to be coming out somewhere on top of the fuel tank (not anywhere near the gas filler cap)
We did note a rubber hose coming from the canister to a point in front of the LR tire, then up and over the tank, toward the area where the leak appears to be coming from (can't see that area on top of the tank as yet).
My questions:
1) Since the EVAP system is supposed to be enclosed (holds vacuum). I suspect that air leaking out toward the top of the tank is indicative of a bad hose or other issue. Is there any reason such an air leak would be "normal"?
2) If this air leak is a legitimate problem, is there any way to see the area of the leak without dropping the tank? I understand there is an access port to get to the fuel pump -- if I get that open, will it make the top of the tank more visible, or accessible?
3) I finally found a tank diagram at AllData, and it shows two fuel cutoff valves. Is this what allows fuel vapors to reach the charcoal canister, while keeping liquid fuel inside? Even if a cutoff valve has failed (theoretically letting raw gas out), I'd think it would still be connected by the hoses to prevent an air leak to the atmosphere.
4) If I need to drop the tank to get to the area of the air leak (assuming it's an issue), it appears I've got to remove the fuel tank protector and exhaust pipe, but I've not seen anything further about the procedure to drop the (empty) tank. What else needs to be disconnected first, and how do you get those points that are hidden? I suspect there is an access from the cargo area to the gas filler hose, and maybe the breather tube - correct?
Lots of questions here, so I'm obviously expecting the worst. Thanks for any guidance.
In looking at the large hose off the vent control valve (at the charcoal canister), I read that one driver had found his hose clogged by dirt dobbers. So to test, I just cleaned it off and blew into it (lung power). I heard air leaking out "somewhere", and with the help of a neighbor, it appears to be coming out somewhere on top of the fuel tank (not anywhere near the gas filler cap)
We did note a rubber hose coming from the canister to a point in front of the LR tire, then up and over the tank, toward the area where the leak appears to be coming from (can't see that area on top of the tank as yet).
My questions:
1) Since the EVAP system is supposed to be enclosed (holds vacuum). I suspect that air leaking out toward the top of the tank is indicative of a bad hose or other issue. Is there any reason such an air leak would be "normal"?
2) If this air leak is a legitimate problem, is there any way to see the area of the leak without dropping the tank? I understand there is an access port to get to the fuel pump -- if I get that open, will it make the top of the tank more visible, or accessible?
3) I finally found a tank diagram at AllData, and it shows two fuel cutoff valves. Is this what allows fuel vapors to reach the charcoal canister, while keeping liquid fuel inside? Even if a cutoff valve has failed (theoretically letting raw gas out), I'd think it would still be connected by the hoses to prevent an air leak to the atmosphere.
4) If I need to drop the tank to get to the area of the air leak (assuming it's an issue), it appears I've got to remove the fuel tank protector and exhaust pipe, but I've not seen anything further about the procedure to drop the (empty) tank. What else needs to be disconnected first, and how do you get those points that are hidden? I suspect there is an access from the cargo area to the gas filler hose, and maybe the breather tube - correct?
Lots of questions here, so I'm obviously expecting the worst. Thanks for any guidance.
Last edited by dgorrie; 10-29-13 at 07:55 AM.
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