It has been three years now since I have changed coolant in my 99 OBW. I annually added a can of Prestone water pump lube and rust inhibitor to the system. Now, I think it is time for a flush and replace the antifreeze. I have also replaced the radiator cap. So far, so good, no issues with HG trouble on my EJ 2.5 phase 1.

 

I have no issues with existing thermostat, however, is it advisable to replace the thermostat? I bought this car used, so I have no idea how old the existing thermostat is.

I'd replace it. Make sure you use an OEM subaru thermostat.

I'd replace it. Make sure you use an OEM subaru thermostat.

 

Thanks, I was thinking of using an OEM thermostat. I have seen pixs here of OEM vs after market. OEM has the quality, after market looked poorly design and low quality.

Plus due to the difference in the shape the response to temperature is different and can cause a lot of weird things happening. I experienced this back in 96 or 97 when I first replaced the thermostat in my Legacy.

Is there a procedure to actually flush the coolant yourself, or do you just drain it and refill?

 

Also what do you do with the old antifreeze? Do parts stores take it back?

I normally will drain all the coolant out I can, fill with water, run the engine and heater to get the water in the heater core, and then drain the water out. Depending on what I get out, I may do that one more time before refilling with antifreeze/water mix.

 

Autoparts stores do sometimes take old oil & antifreeze. Some cities also have local recycling centers that take used oil & antifreeze.