Vacuum coolant filling
 

OK, I'm probably being overly cautious but I'd like the thoughts of others anyway.

Getting ready to change the coolant in my 2009. 10K miles but it's the original factory fill from when the car was built in April of 2008. I'll of course use genuine Mazda FL-22.

My concern is if it's OK to use a vacuum filler since the rotary has o-ring coolant seals rather than traditional head gaskets. For those who don't know how it works you draw a vacuum on the cooling system (25 inches of mercury IIRC) then put a siphon into the coolant jug or bucket open a valve and the vacuum draws coolant into the system. It's enough vacuum to flatten all your hoses.

I doubt it will affect the seals, but seems unnecessary anyway? Just fill and let circulate. Maybe burp the heater hose. Its all in the shop manual, does not need to be complicated.

I agree with Loki. Why do a vacuum? If there is crud in the system you will need to do a flush anyway even if you do a vacuum. Drain, fill, run with new fluid for a few miles and repeat. If the fluid looks good coming out after the flush you will have no issues.

Yep as these guys said it super easy. I did mine several times this summer. Flushed with ro water and filled with engine ice.

using vacuum I can see, but it makes no sense to me going to the extreme of using 25” Hg. Might be fine on a newish build, but as mentioned it may possibly be asking for trouble on an older or unknown quality engine you picked up later used. Been a lot of Renesis engines on here that had failed coolant O-ring seals.