Changing brake fluid

O

okvol

Member
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2014 Mazda 2 sport
Why? I am about to go for a track day at Hallett Raceway May 11th. I normally just Autocross my car occasionally.

The organizer recommended I change to fresh fluid, and I thought to go with higher-temp fluid while I was at it.

So, I bought some Motul DOT 5.1 fluid for the higher boiling point, and it arrives Wednesday.

And I have a simple hand style vacuum pump.

Here is the question: Do I drain the entire system, and refill? Or do I drain the reservoir, refill with new, and pull in new fluid at each wheel (and the clutch)?
Is there a risk of issues letting the system get air into it? DOT 5.1 does not absorb water (and it isn't silicone based either).

I hope someone with a B-spec or similar experience can give me some advice.
 
You shouldn't let air into the system. Just pump it down until it is just below minimum then keep topping up. You will use quite a lot on the first brake as you purge the reservoir and then very little on the other three. As the CX5 has a four channel system, you can do them in any order.
 
The system is a split system so you need to do diagonal corners of the car, so fl with rr and fr with rl.
 
You bleed it just like any other car, pretty sure order doesn't matter as long as you get to them all, at least I have not had any issues. If anything use a turkey baster to empty what you can out of the reservoir just so you have less to push through the system. Then fill it with the new and pump away at the farthest corner for a while making sure that the reservoir never gets low. Once you do the passenger rear move onto the driver rear, and so on as you get closer to the master.

Also since you are fully changing fluid I would drive the car for a couple of days and then check each wheel again.

For me I do a quick bleed before every trackday to make sure that they are good.

Zach
 
I'll use my vacuum pump to empty the reservoir(s), fill with new fluid, and start doing the wheels and then clutch. Just want to get a clean system.

Thanks for the advice. I've change brakes many times, but not fluid. Even helped my dad rebuild slave cylinders on drum brakes back in the 60's.

I just want to have fun on this track day. I'd like to even pass someone, but I will see how that goes. We are going out in packs of five.
 
Thanks for the info. I'm going to use a vacuum pump to prevent the bubbles and pull the fluid through, but I will keep the split in mind.
 
okvol said:
Thanks for the info. I'm going to use a vacuum pump to prevent the bubbles and pull the fluid through, but I will keep the split in mind.
Click to expand...

Unless you put thread sealing tape on the bleeder screw threads you'll never get a bubble free stream of fluid. It's not a PROBLEM, but what happens is it'll pull air past the threads. If you're just bleeding fluid from the system it's not a big deal, you're not putting any appreciable amount of air in the hydraulic circuit. But if you replace a caliper or something it's an exercise in frustration as you'll never know if you got all the air out or not.

If you can, I'd recommend use your vacuum bleeder all around, then have a helper hop in and pump the pedal per my write-up a couple times on each wheel if you want to be obsessive about it(like I am. lol.).
 
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