CX-5 2014 no brake assis on startup cold wheater

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cx-5 2014 awd/mazda 6 2014 GS
Hi, it was very cold outside and I started the car and enter right away into the garage and realise that I was not stopping normally because I have no power brake. My wife (her car) would have hit the wall no doubt since idle was also high... I read that some car can have sticky/frozen brake booster check valve. Ever heard of this on the CX-5 ? or heard of a delay for that vacuum pump on these cars? The brake assis came back after couple seconds. I know very well I should warm up the car at -25c but that is not the point! I could replace that hose including the valve but I just don't want to replace it for nothing... (but thinking now, no vac in booster means valve was not working correctly.. (the car did run fine the day before..)) Thanks.
 
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2019 CX-5 GT 184 2.2 twin turbodiesel auto - Sonic Silver
Welcome to the forum.

I’ve not heard of this before but those are seriously low temps that can have dramatic effects on even the tiniest amounts of moisture. Of course you need to check for anything obvious but I doubt there is much you can do other than do a few little tests before moving after such a cold start up.
 
Anchorman is right. With temps this low you have to be extra cautious. I’ve had brakes freeze to the rotors in severe cold. A lot of things can happen.
 
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2014 Mazda CX-5 GT AWD w/Tech
I've had mine in temps as low as -25F (a bit colder than your -25C!) and have never had an issue with my 2014. That said, I did have an issue with my 2002 Escape and it was indeed caused by a frozen check valve. New valve/hose solved that problem for me then. If part is cheap enough, you could consider it a "cold weather maintenance item"! (drinks)

P.S. - I never warm mine up, just get in it and drive, which is what I do with all my vehicles. Zero problems from doing that.
 
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cx-5 2014 awd/mazda 6 2014 GS
Alright. Yeah newer cars are a lot better in cold (compare to 80-90s with rock solid shifter etc !). But warm a bit bellow -15 is not a bad idea! For sure general safety should not rely on warming a car ! Will probably replace hose. Thanks.
 
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2016 CX-5 GT AWD/ 2016 CX-9 GT AWD
yesterday in 10 degree F morning weather, my 2016 CX-5 GT had the warning lights go on for Emergency Parking Brake malfunctioning (and the "P" switch was blinking on the center console switch). i read that this could happen in -14 to 4 F weather. sure enough, this morning at 20 F, the brake works fine now. so weird....