Blog Car Care Advice Brake Fluid Reservoir Replacements (Process, Cost, FAQs)
Car Care Advice

Brake Fluid Reservoir Replacements (Process, Cost, FAQs)

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Your brake fluid reservoir stores your brake fluid, prevents it from getting contaminated, and allows the brake fluid level to drop naturally as your brake pads wear down

And unlike dynamic brake system components like your brake calipers, brake pads, and the brake booster, the brake fluid reservoir rarely fails.

However, that doesn’t mean that nothing can go wrong with it.

So, when is a brake fluid reservoir replacement needed? 
And how is the replacement performed?

In this article, we’ll cover everything you need to know about brake fluid reservoir replacements, from why you’d need it to how much it’ll cost and an easy way to get it replaced.

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Let’s start answering those questions.

Why Would The Brake Fluid Reservoir Need To Be Replaced?

The brake fluid reservoir (aka brake master cylinder reservoir) is usually constructed of polymer plastics. Over time, the plastic reservoir will get damaged, becoming brittle and developing cracks. 

These cracks may lead to a brake fluid leak

It’s important to note that brake fluid is hygroscopic, meaning that it absorbs water. Cracks will let moisture into the reservoir, contaminating the hydraulic brake fluid. Contaminated hydraulic fluid will, in turn, have decreased boiling points that reduce vehicle braking performance.

However, cracks in the reservoir aren’t the only thing that can go wrong.

Sometimes, the brake fluid reservoir cap needs replacing if the venting or diaphragm gets damaged. When this happens, the cap won’t seal out moisture, which can also affect brake performance.

Now that you know why you might need a replacement, you might be curious about how it’s done:

How Does A Mechanic Replace The Brake Fluid Reservoir?

Replacing your brake fluid reservoir is a relatively complex task that you should leave to your mechanic.

Here’s how the process works:

A. Old Brake Fluid Reservoir Removal

Here’s how they’ll first remove the old brake fluid reservoir: 

1. Access The Engine Compartment

Your mechanic will first need access to the engine compartment. 
To gain access, they’ll open the hood of the car and secure it. 

2. Locate The Brake Master Cylinder

They’ll locate the brake master cylinder, usually at the back of the car engine compartment, on the brake pedal side. 

There will be some tubing attached to the brake master cylinder, usually two or four tubes, to be exact. Each one is a brake line hose that carries brake fluid to the brake calipers at the car wheels.

3. Empty The Brake Fluid Reservoir

Next, your mechanic will unscrew the reservoir cap and empty the brake fluid into a drain container. A simple tool like a turkey baster or a vacuum syringe will work to extract the old fluid. 

They’ll also detach the fluid level sensor.

4. Secure The Brake Master Cylinder And Remove Roll Pins

They’ll then secure the master cylinder body with a vise to keep it from moving while the old reservoir is detached. Then, they’ll remove the roll pins that hold the brake fluid reservoir to the master cylinder.

5. Detach The Brake Fluid Reservoir From The Master Cylinder

Your mechanic will then insert the pry tool (like a flat-headed screwdriver) between the old reservoir and master cylinder to loosen it. Once the brake fluid reservoir is free, they’ll remove the rubber grommet that acts as a seal between the brake reservoir and the master cylinder.

Now, how do they install a new fluid reservoir in your car?

B. New Brake Fluid Reservoir Installation

Here’s how installing a new brake fluid reservoir goes:

1. Install New Grommets In Brake Master Cylinder

Your mechanic will lubricate the new grommets with fresh brake fluid and install them in the master cylinder body. This is usually done by hand (instead of with a tool) to minimize possible damage to the grommet that could lead to a brake fluid leak.

2. Install New Brake Fluid Reservoir

They’ll then seat the new fluid reservoir in the grommets and press down to connect the reservoir with the brake master cylinder.

3. Reinstall The Roll Pins

Your mechanic will reinstall the roll pins that secure the brake fluid reservoir to the master cylinder body. 

4. Fill The Reservoir With Fresh Brake Fluid

Finally, they will fill the new brake reservoir with fresh brake fluid to the correct fluid level. Brake fluid starts degrading fast, so they’ll need to use fresh fluid from a new container.

Now that we’ve covered the basics of why you need a replacement and how it’s done, let’s go over some FAQs:

4 Brake Fluid Reservoir Replacement FAQs

Here are some answers to some reservoir replacement questions you may have:

1. Can I Replace The Brake Fluid Reservoir Myself?

While it’s possible to DIY this type of braking system replacement, it’s always better to let a professional mechanic do it

Here’s why:

Firstly, a brake fluid reservoir replacement may involve some contact with brake fluid. Some brake fluid is likely to spill when the reservoir is separated from the brake master cylinder. Brake fluid is corrosive and toxic, so you must be very careful when handling it.

Secondly, the brakes may require bleeding to eliminate possible air bubbles after a reservoir replacement and refill. As a result, you’d likely need a bleeder kit on hand and know how to use it. 

And thirdly, incorrect reservoir replacement can lead to a major brake fluid leak, a damaged grommet, or even a broken reservoir nipple if not handled with care. 

That’s a lot to consider for what may seem a straightforward task, so get a mechanic to do it and save yourself the hassle.

2. Do I Have To Replace The Master Cylinder Along With The Fluid Reservoir? 

Most of the time, no
The brake reservoir sits on a grommet (or two, depending on master cylinder type) that’s fitted to the top of the brake master cylinder and is separable.

As a result, your mechanic can usually replace the brake fluid reservoir without needing a new master cylinder — unless it’s one of those designs that mold both units together.

3. What’s An Easy Way To Replace The Brake Fluid Reservoir?

Replacing the brake fluid reservoir isn’t just a matter of popping off the plastic reservoir from the brake master cylinder and putting on a new one. Filling it with the right brake fluid type or even conducting a complete brake fluid change are just some of the considerations that need to be made.

To ensure all the little details are covered, your best bet is to get a good mechanic to deal with your braking system fixes. 

They should ideally:

And luckily, AutoNation Mobile Service fits the bill.

AutoNation Mobile Service is a convenient mobile vehicle repair and maintenance solution, and here’s why you’ll want them to handle your repairs:

Now, how much is all this going to cost?

4. How Much Does A Brake Fluid Reservoir Replacement Cost?

On average, you can expect to spend between $209-$236 for a brake fluid reservoir replacement. Labor costs typically range within $100-$126, while replacement parts cost around $109-$111. 

These numbers don’t take into account taxes and fees. 
They also don’t factor in the make and model of your vehicle or your location.

For an accurate estimate of how much your brake fluid reservoir replacement will cost, fill out this form.

Final Thoughts

While it may not be a very common brake system repair, a brake fluid reservoir replacement is something that should be left to a professional. 

But don’t worry. 

Whether it’s a master cylinder reservoir replacement, caliper change, or a clutch fix, you can always contact AutoNation Mobile Service, and their expert mechanics will drop by, ready to sort things out!