How to Clean Out Brake Fluid Reservoir? 2015 CX-5

[anyman]

Looking to do a long-overdue brake fluid exchange/flush on my 2015 CX5 GT. Fluid desperately needs changing but I have what appears to be black cloudy bits floating around in my fluid. Could be deteriorating brake hoses or even the underside of the cap deteriorating. I'd like to try and clean out the reservoir the best I can and monitor for a week to see if those black bits resurface and maybe inform me better on if I need to change out my brake hoses.

Is there a relatively easy way to remove the reservoir from the master cylinder to clean it out? Or should I just try and suck as much of that black crap out with a hose/pump and refill with new fluid?

 

[Silly Wabbit]

2013-2023 Mazda CX-5 Master Cylinder Reservoir KDY3-43-55Z | OEM Parts Online

2013-2023 Mazda CX-5 Master Cylinder Reservoir KDY3-43-55Z

mazda.oempartsonline.com

Looks rather simple to remove. You might need to replace the 2 gourmets tho.

 

[murky]

Normally as part of a brake job I bleed the brakes until everything runs clear. The first step for that is sucking the fluid from above the master cylinder so I don't have to pull it all the way through the system.

On my CX5, it was difficult to get much of anything out of the reservoir, so I just ran more fluid through than I otherwise would have.

I was find with that, but didn't have bits floating around. Bits would concern me.

 

[anyman]

@murky I haven't really explored the reservoir but it looks like there are baffles in the way to be able to stick a hose down towards the bottom, right?

 

[murky]

@murky I haven't really explored the reservoir but it looks like there are baffles in the way to be able to stick a hose down towards the bottom, right?

That sounds right, and I went in with the mission of getting the job done. My few minutes of poking around didn't reveal a clear process to getting a syringe or tube deep enough into the fluid reservoir to matter.

 

[anyman]

I know nothing about the inner workings of a master cylinder but do you think sucking that cloudy black stuff through the cylinder could cause a problem? The stuff is really weird…it’s not chunks or anything remotely solid. It’s like dust suspended in the fluid.

 

[skid00skid0]

You might be able to use a straw from a spray can, like WD40...

 

[Conrad 16.5]

While I haven't yet done a brake fluid flush on my CX I've done it many a time on my other vehicles.

I use a shopvac to suck out the junk from the brake fluid reservoir. I'm sure that you're scratching your head saying WTF? That would make a major mess, right? Nope.

I use the vac to create a vacuum in a glass bottle. In the bottle I also have a small bit of plastic tubing. One end of the tube is in the bottle (the end must be kept above the level of the fluid in the bottle) the other end I use to suck out the junk at the bottom of the reservoir. Care must be taken not to suck out too much as you don't want the port in the bottom exposed to the air. Air in the lines is bad, very bad. Keep an eye on the bottle and don't let it become too full. You shouldn't have to suck out that much anyway.

YMMV

 

[anyman]

@Conrad 16.5 Thanks for the info. So does your plastic tubing reach the bottom of the brake fluid reservoir? I have black cloudy "stuff" in several areas of the reservoir (probably at each baffle level...not even sure those are baffles).

Even if I can get a tube to the bottom I can even use my mouth (I know, I know) to suck some of the fluid/gunk into a long tube (so I don't get any in my mouth obviously) and into a container.

 

[Conrad 16.5]

@Conrad 16.5 Thanks for the info. So does your plastic tubing reach the bottom of the brake fluid reservoir? I have black cloudy "stuff" in several areas of the reservoir (probably at each baffle level...not even sure those are baffles).

Even if I can get a tube to the bottom I can even use my mouth (I know, I know) to suck some of the fluid/gunk into a long tube (so I don't get any in my mouth obviously) and into a container.

As I said above, I have yet to do this work on the CX. I know that there's a 'basket' inside the reservoir and it's in the way of reaching the bottom with a vac tube. I'm pretty sure that this thing can be removed or moved so that access is easier.

Your long tube method should work, just don't suck too hard (I find it strange saying that on a car forum)

 

[anyman]

So my filter basket is missing...I'm guessing the tech who maybe did the last bleed omitted it.

I tried to stick some standard 1/4 plastic tubing into the reservoir...yeah, not gonna work. I can get it into the first "level" but it hits the next "baffle" and won't go any further. Plus the cloudy stuff has settled at each level so I'm not even sure how I can stir it all up to try to suck it out anyway.

My guess is that these baffles are there to deal with acceleration and incline changes (so air doesn't enter the system)...just a guess. I see them on my Tacoma as well.

Anyway, without removing the reservoir I don't think I'm getting this crud out. What I may do is just move forward with the bleed...I'm sure this stuff is already throughout the system anyway. At some point here I'll tackle removing the reservoir but I'm sure this is going to introduce a bunch of air into the system.

Right now I want to focus on safety and just getting fresh fluid in there.

 

[yrwei52]

So my filter basket is missing...I'm guessing the tech who maybe did the last bleed omitted it.

I tried to stick some standard 1/4 plastic tubing into the reservoir...yeah, not gonna work. I can get it into the first "level" but it hits the next "baffle" and won't go any further. Plus the cloudy stuff has settled at each level so I'm not even sure how I can stir it all up to try to suck it out anyway.

My guess is that these baffles are there to deal with acceleration and incline changes (so air doesn't enter the system)...just a guess. I see them on my Tacoma as well.

Anyway, without removing the reservoir I don't think I'm getting this crud out. What I may do is just move forward with the bleed...I'm sure this stuff is already throughout the system anyway. At some point here I'll tackle removing the reservoir but I'm sure this is going to introduce a bunch of air into the system.

Right now I want to focus on safety and just getting fresh fluid in there.

I believe the missing basket / screen could contribute the existence of black cloudy bits in your brake fluid reservoir. You best chance is to remove it and clean it as much as you can. Or just get a new reservoir (your missing strainer should also be included and it can prevent dirt dropping into the reservoir) with 2 o-ring seals although the price is high.

Brake fluid is corrosive it’ll damage the paint. Of course I won’t suck it either.

 

[anyman]

@yrwei52 Yeah, I don't really know to be honest. I think it's either deteriorating brake fluid (several videos on YT show their fluid looking similar or much worse to mine) or the lines themselves. They ended up just putting in new fluid.

If I were to replace/remove the reservoir, what's involved with that? It looks like I have to remove a few lines. The mystery line is that clutch reserve line. If air is introduced into that, how do I even bleed that?

Oh...and I found a better way to remove the fluid that doesn't involve me accidentally ingesting brake fluid

 

[Conrad 16.5]

@yrwei52 Yeah, I don't really know to be honest. I think it's either deteriorating brake fluid (several videos on YT show their fluid looking similar or much worse to mine) or the lines themselves. They ended up just putting in new fluid.

If I were to replace/remove the reservoir, what's involved with that? It looks like I have to remove a few lines. The mystery line is that clutch reserve line. If air is introduced into that, how do I even bleed that?

Oh...and I found a better way to remove the fluid that doesn't involve me accidentally ingesting brake fluid

Glad to hear that you won't be sucking in any brake fluid!

You have a manual transmission in your CX? Another layer of complexity. I wouldn't go through the trouble of removing the rez, there has to be a way of getting a small diameter piece of tubbing down in there. I haven't looked closely though.

 

[yrwei52]

You have a manual transmission in your CX? Another layer of complexity.

The OP has a 2015 CX5 GT, it can’t have a manual transmission. Only CX-5 Sport offers manual transmission with a 2.0L for 2015 MY.

I had done brake fluid bleeding on the vehicle with manual transmission where the clutch uses hydraulic system with brake fluid. It shouldn’t be too complicated but just have to do one extra bleeding at the bleed valve near the clutch area.

 

[Conrad 16.5]

The OP has a 2015 CX5 GT, it can’t have a manual transmission. Only CX-5 Sport offers manual transmission with a 2.0L for 2015 MY.

I had done brake fluid bleeding on the vehicle with manual transmission where the clutch uses hydraulic system with brake fluid. It shouldn’t be too complicated but just have to do one extra bleeding at the bleed valve near the clutch area.

Yes, I know this but was confused when the OP stated,

"f I were to replace/remove the reservoir, what's involved with that? It looks like I have to remove a few lines. The mystery line is that clutch reserve line. If air is introduced into that, how do I even bleed that?"

 

[anyman]

Did the bleed today. Aside from some issues using the Motive brake bleeder it went relatively smoothly. I was able to suck a large majority of the old fluid and black cloudy bits out using a 1/4 tube that was more flexible. There’s not way I was getting that tube all the way to the bottom of that reservoir though.

Another interesting thing happened. The pressure from the Motive bleeder actually forced a lot of the old fluid in the reservoir upward towards the top…no idea how but it did. Then I was able to remove the cap then suck the old fluid out. Reservoir isn’t spotless but it looks 80% better.

 

[Conrad 16.5]

Did the bleed today. Aside from some issues using the Motive brake bleeder it went relatively smoothly. I was able to suck a large majority of the old fluid and black cloudy bits out using a 1/4 tube that was more flexible. There’s not way I was getting that tube all the way to the bottom of that reservoir though.

Another interesting thing happened. The pressure from the Motive bleeder actually forced a lot of the old fluid in the reservoir upward towards the top…no idea how but it did. Then I was able to remove the cap then suck the old fluid out. Reservoir isn’t spotless but it looks 80% better.

What kind of tubing did you end up using? I was thinking that maybe some of that air line tubing that's used in aquariums might work. Yes, the diameter is small but it's very flexible and could fit into the tight areas of the reservoir.

 

[anyman]

@Conrad 16.5 I used a piece of tubing that came with the brake bleed bottle I bought. It's similar to aquarium tubing but thicker...which limited access. I wish I had some aquarium tubing on hand because the may have reached down a bit further.

I'd love to just take apart a reservoir to see how in the hell it's compartmentalized. Just shining a light through the side of it doesn't reveal much.