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we all know that most of the shops just use universal coolant for years with no problems(sometimes except EU cars). So I think I will just replace one gallon - that's it.

So I got a headache again: My water pump failed at 105K(right after I bought the car), so I assume no one changed coolant since beginning. Are u trying to say that Peak Full Force won't work?

I think I am going to drain 1 Gal of original green(or blue) coolant(I tested it with a tester that has plastic balls inside - 2 balls were floating only which tells the freezing point is -15C) and will add 1 Gal of brand new PEAK Full Force (water(7732-18-5), Ethylene Glycol(107-21-1), Diethylene Glycol(111-46-6), Denatonium Benzonate(3734-33-6) and Proprietary inhibitors)- an AI said it will work but I don't really want to trust an AI.

Also I got another idea: - loop the heater core in-out; - remove the thermostat; - disconnect the lower radiator hose(from radiator) and put in a bucket with fresh coolant; - disconnect the upper radiator hose(from radiator) and put it in an empty bucket; - start the engine up and let the water pump do the job(I hope the engine will not seize working for 10-15sec). What do u think, guys? P.S.: seems like it will not work because of the water outlet inner design...

I have got one canister of PEAK Full Force (water(7732-18-5), Ethylene Glycol(107-21-1), Diethylene Glycol(111-46-6), Denatonium Benzonate(3734-33-6) and Proprietary inhibitors) + 2 canisters of PEAK (free of 2-EHA, silicate, nitrite, borate, and amines. Compatible with any color or type of antifreeze and coolant.) Now I think if I could disconnect the radiator and the heater core, loop inlet and outlet(heater core) and apply water from garden hose to the lower or upper radiator hose inlet to rinse the old coolant out of the engine(instead of using the air - but I am still not sure if it works this way).

As I said - my coolant is already premixed. So if the manufacturer of that coolant says it works with all makes and models(which means I can mix it up) - someone would definitely sue them if it wouldn't work then.

I will not trust someone working on my car. I used to work as a car mechanic for years. Now I'm not sure which way is the best to get rid of the old coolant and looks like no one knows(here and YT). So probably I will drain 1 gallon and add 1 gallon premixed I got(it says fits for all cars)...

probably, but I already bought premixed coolant and can't return it. So I am looking for the best way to push the old coolant out(I do have a vacuum tool to fill it). I can use a big compressor(like 20 Gal) but i don't think I need it because I will not apply more than 18-20psi at the time. I am still not sure about the best way: I have an air adapter to the reservoir, I can disconnect the heater core hoses, plug one pipe on the water outlet and provide pressure to the other one(keeping the radiator drain plug open), I can easily take the thermostat out...

I plan to do this procedure tomorrow. I plan to drain over a drain plug, remove the thermostat, connect the housing back and apply about 15-20psi air pressure trough the expansion tank to get rid of all the old coolant. Then I will install the thermostat back, vacuum the system and fill it up with a fresh coolant. But the question: if I will remove thermostat - it's going to leak there because of no thermostat(like 1mm thick) should I make some gasket(from thick paper or a plastic) and put in next to the thermostat o-ring?

BoringAccountant, is it worth to spend $500 for the device and software for 09 MKX if I am planning to use regular gas? I drive in range ~ 1-1.3k rpm(not aggressive) I feel a huge difference compare to my gf 18 Crosstrek(way quicker). I plan to keep this MKX for years, 125k on it only, new water pump, timing chain, phazers, PTU drain plug w/fresh fluid, remote start, backup camera etc.

mine is 2009, WP failed at 115k, coolant is clean(green) - I think nobody changed since 2009. I'm thinking should I change it if everything's fine?

I plan to do it also. I think to drive, get the thermostat open and apply some pressure using a reservoir cap with a fitting and connect an air inflator to it.

what have u found?

what's the problem u think? the filter inside the can doesn't allow enough air go trough? The hoses are pretty thick, but they are regular, like a heater core hoses. So why it works flawlessly then and does its job? If it works fine for 400+ miles - do u think is there any danger for the engine?