Okay guys I'm new-ish to working and trouble shooting my vehicles but I'm getting stumped. I have a 2004 forester xs with 120,000 on motor, 250,000 on body. Only 1 check engine code which pertains to the EGR valve that's needs replaced. About a month ago the car randomly started overheating and my upper radiator hose failed and shot coolant out during my 1 hr drive home from work. I had assumed it was a bad hose and replaced it only to find I was wrong later after the same thing happened to the lower hose do to the pressure building in coolant system. I did some research and changed thermostat and radiator cap. Car started overheating again. Took it to a mechanic and they said radiator has blockage in it and he replaced thermostat. I then did the work myself and replaced radiator and burped the system when I refilled it.
Now--- the car runs for about 3-4 days (1 hr 2x a day) until finally the coolant has made it's way into the plastic overflow container filled it completely up. The coolant will NOT go back into the radiator after this point and I noticed after I drive it like this that there are small bubbles for 10 or so minutes in the overfilled overflow container. I've been back to same mechanic who then tested the coolant for gas to see if it was a head gasket problem. The coolant test came back fine with no gas in coolant?
Things I should mention: -Both heat and air work fine all the time. -The fans kick on at when car reaches temp. -The car only starts overheating while idling now and is fine when driving. - I smell burning coolant after it's at temp and i drive to or from work. I assume its pushing it's way out of overflow bottle and burning off on engine? -the car runs fine other than having very sluggish/slow acceleration when merging and climbing to speed on highway -My dad who has worked on vehicles for years suggested maybe the cat converter could be clogged and causing pressure in system?
Any tips or suggestions are welcomed, I appreciate it!!