Brake Fluid Drain/Fill, Mazda dealer says NO

shadonoz

SkyActiv Member
Contributor
:
State of Jefferson
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2017 CX-5 GT AWD+
The fluid level in the master cylinder goes down over time because pad wear allows the caliper pistons to move further inward, pulling fluid from the reservoir.
But only if an equal volume of air enters the reservoir. Otherwise there'd be a vacuum and it couldn't draw-down the brake fluid.
Both right, so you can be sure that it's not sealed. Otherwise water wouldn't get into it, either.
 
But only if an equal volume of air enters the reservoir. Otherwise there'd be a vacuum and it couldn't draw-down the brake fluid.
that is how every hydraulic brake system I know of has worked - it is possible however to include a variable volume (elastic) device in the system and completely seal it


I asked b/c that would be unusual. It is also important b/c if the system is open to the air, then moisture in the air will cause moisture in the brake fluid, and THAT means the moisture (water) will boil under hard, prolonged braking, thus lowering the brake function.

So, change all the fluid every 2-3 years.

I also use a small brake fluid tester but mostly for fun as I dunno how accurate a $15 device will be.

Remember, it is TIME, not mileage - moisture will equilibrate while the vehicle sits in your garage.
 
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2016.5 CX-5 GT AWD titanium/black 2016 Miata Club ST MT white
But only if an equal volume of air enters the reservoir. Otherwise there'd be a vacuum and it couldn't draw-down the brake fluid.
What about the rubber 'bellows' in the cap of the brake fluid reservoir? I'm not arguing that the system is sealed but there are the bellows to consider.
 

Kaps

Contributor
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CX-5 Touring 2016.5
People still go to the dealer to let them touch their cars. Here you go...

Dealers did not touch my cars since new.

Brake flush done at 44K in both. At least I know what got out and what got in in terms of fluids.
I would say you are in minority - majority get their work done through dealer.
 
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2014 Ford Explorer Sport, 2009 CX9(Wife's)
What about the rubber 'bellows' in the cap of the brake fluid reservoir? I'm not arguing that the system is sealed but there are the bellows to consider.
I was just going to mention that.

Not sure on the CX5, but I know on my old mustang, it has the rubber bellows to seal the reservoir. The cap has a small hole to allow the bellow to expand into the reservoir as the fluid goes down (pad wear).
 
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CX-5 AWD, 2017
Here in Sweden, they change/flush brake fluid every two years at Mazda workshop along with regular service. My Cx5 (2017) is scheduled for service in two weeks time and this time it is going to have brake fluid flush along with regular service.
 

erhayes

Contributor
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Mazda CX-5 FWD Touring
The CX5 has a rubber seal that protects the BF against absorbing air by moving down as the brake fluid goes down in the reservoir. I think the old days of flushing brake fluid every two years or 24K miles is gone. Just check the reservoir for fluid level (don't open to atmosphere and disturb the rubber diaphragm seal) and change the fluid when doing a pad change. Ed
 

madar

Contributor
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2016.5 CX 5 Touring AWD, 2015 SCION XB
Just another misinterpretation from a Mazda Service Advisor, won't be the first and won't be the last, although this one seems like one of the more ridiculous ones I've heard from a dealer. Maybe she was thinking about transmission fluid. I think everybody here knows a brake fluid change is a good thing from time to time. Too bad the "professionals" don't.
 
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2019 CX-5 Signature Soul Red Crystal Metallic
So many clueless people at a dealer, you gotta go in person so you can interpret who clearly doesn't know what they are talking about and who does. Luckily the guys at my choice dealer are generally knowledgable dudes. They know me by name since I'm always there for parts lol (almost never for service).
I just had my first service at my dealer (car only has 9000km on it), and it blew me away when I asked the guy to have them check my transmission fluid level because several people here on this forum reported lower-than-normal levels in their transmissions.

I was told "its a sealed unit, there is no dipstick".. For which I know he's either 1) Misinfomred or 2) Lying because they didn't want to check it.

THe whole experience was lacklustre. NO "how's the new car!" no "Enjoying the car?, anything to report?" nothing. Just... ^ that.

I'll do one more oil change there, then I'm out.
 

ColoradoDriver

Gen-1 Kodo Design
Contributor
:
Denver, CO
:
2014 CX-5 Touring
I just had my first service at my dealer (car only has 9000km on it), and it blew me away when I asked the guy to have them check my transmission fluid level because several people here on this forum reported lower-than-normal levels in their transmissions.

I was told "its a sealed unit, there is no dipstick".. For which I know he's either 1) Misinfomred or 2) Lying because they didn't want to check it.

THe whole experience was lacklustre. NO "how's the new car!" no "Enjoying the car?, anything to report?" nothing. Just... ^ that.

I'll do one more oil change there, then I'm out.
God I have seen that myth perpetuated so much. I believed it for the longest time myself before I read up on people doing drain/fills on this forum.
 
The CX5 has a rubber seal that protects the BF against absorbing air by moving down as the brake fluid goes down in the reservoir. I think the old days of flushing brake fluid every two years or 24K miles is gone. Just check the reservoir for fluid level (don't open to atmosphere and disturb the rubber diaphragm seal) and change the fluid when doing a pad change. Ed
where is the seal located?

how is expansion of brake fluid handled?
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
The CX5 has a rubber seal that protects the BF against absorbing air by moving down as the brake fluid goes down in the reservoir. I think the old days of flushing brake fluid every two years or 24K miles is gone. Just check the reservoir for fluid level (don't open to atmosphere and disturb the rubber diaphragm seal) and change the fluid when doing a pad change. Ed
The brake fluid reservoir on my previous 1974 Chevrolet Impala has a rubber cap seal to protect the brake fluid. The thing is the 2-year brake fluid replacement is a standard maintenance schedule for Mazda CX-5 in other countries, but NOT in the US. Most Euro vehicles sold in the US also have 2-year brake fluid replacement schedule.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
where is the seal located?

how is expansion of brake fluid handled?
In very old days such as my 1974 Chevy Impala the rubber cap seal is a whole piece to cover iron brake fluid reservoir which has two round-cylinder flexible "bubble" to handle brake fluid expansion and contraction. For newer plastic brake fluid reservoir there should be a small vent hole on cap.
 
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2019 CX-5 GT 184 2.2 twin turbodiesel auto - Sonic Silver
where is the seal located?

how is expansion of brake fluid handled?
Unless the reservoir is different than the Euro one there isnt one. (and while I didnt specifically look, I didnt notice anything when I was noseying at a rental). I can only think Ed is mistaken.
 

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2016.5 CX-5 GT AWD titanium/black 2016 Miata Club ST MT white
in very old days such as my 1974 chevy impala the rubber cap seal is a whole piece to cover iron brake fluid reservoir which has two round-cylinder flexible "bellows" to handle brake fluid expansion and contraction. For newer plastic brake fluid reservoir there should be a small vent hole on cap.

fify
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
In very old days such as my 1974 Chevy Impala the rubber cap seal is a whole piece to cover iron brake fluid reservoir which has two round-cylinder flexible "bellows" to handle brake fluid expansion and contraction. For newer plastic brake fluid reservoir there should be a small vent hole on cap.
fify
Thank you! (drinks)
 
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