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Do You Have To Bleed All 4 Brakes When Changing A Caliper?


I ask myself this every time on work on the brakes of an old car. Will I get away with bleeding one caliper? – because you know the bleed nipples are as rusty as hell.

It’s common practice to bleed all four brake lines after opening any one brake line. However, if the brake line you open is an independent brake line, then no, you don’t have to bleed all 4 brakes

This post will cover identifying your brake line type, the brake bleeding procedure, and the sequence. The type of brake fluids you can mix and the types you must never mix.

Check out the beginner brake repair page for step-by-step illustrated guides.

A common mistake when working on brakes is to mix incompatible brake fluid types. This simple mistake can be costly as the system must be flushed, and it’s possible to damage components. I’ll tell you what brake fluids you can mix and what fluids you must never mix.

Calipers work hard and are a common cause of brake issues; that said, contaminated brake pads and rotors can mimic a caliper issue. Here’s a link to a post on exactly that topic – Brakes stopping abruptly

A faulty flexi brake line hose can mimic a faulty caliper also; you’ll find a post that covers that subject here – Brake hose causing caliper to stick

You may find the brake resources page useful; it’s a fluff-free guide to DIY brake repairs.

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Brake Caliper Bleed Nipple

I know bleeding all four wheels can be a lot of extra work, especially if the bleed nipples look like they’re really rusted solid.

Brake caliper rusty nipple

I call it nipple roulette – Will they or won’t they shear off. If they do, you’re looking for a replacement caliper.

I understand the dilemma, but sometimes you won’t have a choice. You’ll have to bleed all wheels. To figure out if it’s OK to bleed just one caliper, we’ll first need to figure out if the brake line is an independent line. (most are)

Independent Brake line

So how do I know if it’s an independent brake line? Most modern cars will employ independent brake lines. It’s easy to figure out. If you have an ABS unit, check and see how many distribution lines there are.


They’ll be marked most likely FL (Front Left), FR (Front Right), RR (Rear Right), and RL (Rear Left).


The distribution lines are all the same diameter and feed each wheel.

The two feed lines are connected to the master cylinder and are larger in diameter.

While having four brake lines from the modulator out to each of the four wheels means you have a four-channel independent system (technically, it isn’t really fully independent, as the brake lines are typically paired diagonally – FL paired with RR, and FR paired with RL)


That said, it’s OK to bleed just a single caliper on this type of system (so long as the brake fluid doesn’t or hasn’t drained below the low-level mark in the brake fluid reservoir)


Tandem master cylinders mean the orange and green brake circuits seen here are independent of each other.

Meaning if the orange circuit failed, the green would still perform.

The lines are typically paired diagonally.

If your car was made in the last 20 years, you probably have an ABS. Early ABS systems were three channels, meaning the front calipers have independent brake lines, and the rear are paired. This is also a popular pre-ABS brake line layout.

Car brake line diagram

If you have a 3-channel ABS, either of your front calipers may be bled independently.

But if you are working on any of the rear calipers (or cylinders), you’ll need to bleed both. 

But most folks (Vehicles younger than 20 years) will probably have a tandem master cylinder with a diagonal brake line layout or paired layout front and back.

In this type setup, it’s Okay to bleed just one caliper.

Opening Brake Caliper Bleed Nipple

Bleeding car brakes

Opening brake nipples can sometimes be the hardest part of the whole job. I usually approach them with a wire brush and WD40 well before putting a wrench on them.

A wrench is often not much use, as the small nipple head is usually stripped. The vice grips should do the job; unfortunately, we can’t use heat to help move it. The caliper pistons have rubber seals. If I can get them out, I like to replace them, but be sure that the seat of the nipple is identical to the old ones. Otherwise, they’ll leak.

Brake Bleeding Sequence


The process is simple enough. If you’re bleeding all the brakes, bleed paired brake lines, typically Rear Left followed by Front Right, then Rear Right, and finally Front Left.

Some manufacturers may have a different recommended sequence, some recommend starting fartherst from the brake fluid reservoir and finish at the reservoir, don’t swet this detail, as it isn’t that important unless your system ran dry.

Older vehicles may be a little different, some may have one brake line feeding both rear wheels, if that’s you then you’ll need to bleed both of rear wheels before moving to the front right and finally front left of the vehicle.

Braking System Checklist

  • Check brake fluid level every month
  • Change brake fluid every three years
  • Bleed brakes yearly
  • Check brake pad/shoe wear every three months
  • Check the condition of rotors and drums every six months
  • Check for brake cylinder/calipers fluid leaks every six months
  • Check and adjust the emergency brake yearly
  • Check the condition of brake lines and hoses yearly
  • Check operation of brake equalizer yearly (if fitted)

You can check where these components are and what they do here – Brake component location & function

Brake Fluid Types

Brake fluid cap

Most brake fluid types are hygroscopic. They absorb moisture from the atmosphere. Brake fluid should be stored in a sealed container, and your brake fluid reservoir cap shouldn’t be left open for extended periods.

So what’s the problem with a little moisture?

When brake fluid has a high moisture content, the heat from the brakes is absorbed by the brake fluid. The moisture in the fluid then boils and turns to steam = Spongy feeling brake pedal.

Also, the moisture, if ignored, will cause rust to form inside the calipers and master cylinder. This can’t be cleaned. They’ll need to be replaced. Moisture will make its way into the fluid even with a good sealing reservoir cap, so that’s why it’s important to change or flush your brake fluid every three years.


Brake fluid types are coded, and the type to be used will be marked clearly on your fluid reservoir cap. It will be marked Dot 3, 4, 5, or 5.1. I like to keep things simple. You can divide brake fluid into two types – Glycol or Silicone based.

Without getting too far into the weeds, Glycol-based fluids are compatible but ideally shouldn’t be mixed because they have different boiling points, but you won’t hurt the car if you do mix them. Glycol-based compatible families of fluids are Dot 3, Dot 4, and Dot 5.1.

What’s the difference between Dot 3, 4, and 5.1?

Basically, the amount of heat they withstand before boiling, the higher is better. But use whichever fluid is marked on your cap. Also important to note is that Glycol-based fluids will strip paint, so be careful splashing this stuff around.

Silicone-based Dot 5 fluid must not be mixed with Glycol-based Dot 3, 4, or 5.1. If mixed, these fluids will become sludge in the system, and the pedal will feel like a pillow. The mixed fluids will damage your calipers, master cylinder, and ABS if left in the system.

Dot 5 is used in all military vehicles, and since it doesn’t absorb moisture, it doesn’t need to be changed at regular intervals. It’s excellent in colder climates as the low moisture content prevents freezing fluids and is paintwork friendly.

Dot 5 is more compressible than the Glycol types, so the pedal sometimes feels slightly spongy.

Check out this post where I cover adding brake fluid in a little more detail – Can I just add brake fluid?

If you need brake fluid or any brake system parts, check out the brake tools I use here on the Brake repair tools page

Brake Bleeding

Bleeding the brakes is traditionally done by two people. I remember sitting in the driver’s seat, barely reaching the brake pedal. I was the brakeman while my father issued the pump and hold commands.

When it comes to bleeding the brakes, you can do the two-man pump, hold, and release, and there are a couple of other MacGyver-type hacks on this method, or go the pro road and buy a proper vacuum brake bleed kit.


Check out this post if you don’t fancy buying a pro brake bleeder. I cover making a DIY Homemade bleeder in minutes – How to bleed brakes without brake bleeder kit

You might like this post also, How to wind back caliper pistons without tool

Vacuum Bleed Kit Preferred

A bleed kit is preferred, especially on older cars, because pumping the brake pedal can cause damage to the master cylinder seals as they’re pushed further down into the cylinder than normal.

In my workshop, I used a couple of different types. One type I use applies pressures to the brake fluid reservoir, and I simply open each bleed nipple in sequence. But you do have to keep a close eye on the fluid level, though.


And the second and preferred method is the vacuum type. A handheld vacuum pump is used to draw fluid from each bleed nipple.

I wrote a post recently about using the vacuum-type brake bleeder – Flush brake fluid system

I’ve listed a vacuum brake bleeder on the Brake repair tools page that’s perfect for home use, or check it out here on

MacGyver Style Brake Bleeding

You’ll need a quart of brake fluid, WD40, a wire brush, a clean rag, a selection of small-size ring wrenches, vice grips, 3 feet of clear hose, and a container for waste fluid.


Two-man pump, hold, and release method.

Typical brake bleed sequence



  • Pump Brakes 5 times
  • Hold Brake Pedal Down
Holding down brake pedal
  • Pump Brakes 5 times
  • Hold Brake Pedal Down


opening brake bleed nipple
  • Start With the LR (Left Rear)
  • Apply grease around the bleed nipple threads (prevents air contamination)
  • Open the Nipple to release fluid
  • Close Nipple
  • Repeat 3 to 4 times


Top up brake fluid
  • Top up Brake Fluid
  • Move to FR (Front Right) and repeat


Brake fluid
  • Top up Brake Fluid
  • Move to RR (Rear Right) and repeat
  • Finally, finish at the FL (Front Left)

If your brake fluid looks like the fluid in the image above, I’d go ahead and flush the whole system, check that process out right here – Brake system flush

You can check out all the tools I use to repair brake systems, including workshop manuals, here on the Brake repair tools page, or make your own homemade brake bleeder, How to bleed brakes without brake bleeder kit

Brakes are serious business; if you aren’t confident they are right, check them with your local mechanic.

Check out the beginner brake repair page for step-by-step illustrated guides.

Check out the DIY Brake Repair page for easy-to-follow brake repairs and troubleshooting tips.

Wheel off brake inspection

Other brake posts you may find helpful:

About the Author

John Cunningham is a Red Seal Qualified automotive motive technician with over twenty-five years of experience in the field. When he’s not writing about car repair, you’ll find him in his happy place – restoring classic cars.

Related Questions

How often should you start a classic car? A classic car should be driven once a week. Take it for a 30-minute drive. Just starting a classic car is OK for charging the battery but has a negative effect on the oil and exhaust system. Short trips cause condensation, which is the enemy.

How do you store a classic car? A classic car should be stored in a garage, preferably heated. If you don’t have a garage, then a breathable car cover is the next best thing. Avoid plastic as it traps condensation. Keep your gas tank full and use a gas stabilizer and battery maintainer.