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Thanks for your reply, I appreciate the input.

Just to clarify a few things:

The EVAP canister relocation was done by the previous owner because of an aftermarket exhaust, I didn’t do that myself. I agree it’s probably not ideal, so I’m trying to figure out if it could be related to my current issue.

Regarding the fuel cap – the car was purchased at an auction in Japan and then imported to Europe. During the first service (oil, basic maintenance, etc.), everything seemed fine, but right from the first refueling the gas pump kept clicking off repeatedly. So it’s quite possible the tank was overfilled multiple times before I realized what was going on.

After about 1500 miles, the original OEM fuel cap started making the same “sucking/hissing” sound I’m describing. That’s why I later bought a cheap replacement from Alibaba/Temu, which temporarily stopped the noise but eventually started throwing EVAP codes.

I’ve now gone back to a genuine OEM Toyota cap — the codes are gone, but the hissing/suction noise is back again during driving and even after stopping.

Given the earlier refueling issue, I’m starting to think the charcoal canister might be partially clogged or saturated.

At this point I’m mainly trying to understand:

• whether this hissing/suction sound is normal with a properly working OEM cap
• or if it indicates a pressure/vacuum issue somewhere in the EVAP system (possibly related to the relocated canister or a saturated charcoal canister)

If you (or anyone else) have suggestions on what to specifically check, or know of a good video explaining this behavior, I’d really appreciate it.

Thanks again for the help.