Toilet bubbels when flushing

[pacman]

Hello,

So i have this one toilet that bubbles up when i flush. I've poored drano and used a plunger just in case there was some sort of clog, but neither has helped.

Basically, it looks like someone is blowing bubbles from underneith the bowl, the water rises and then slowly goes down. There isnt much force either, seems like a very weak flush.

Thanks,

pacman.

[DIY Guy]

I suspect the vent line may be blobked or partially blocked. It is causing a siphon condition in the drain line.

Check the vent lines if you are comfortable working on your roof, otherwise contact a plumber.