2018-2020 Buick Enclave Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 2018-2020 Buick Enclave uses GM approved DOT 3 brake fluid, and Buick's maintenance schedule says to replace the brake fluid every five years. The fluid spec is printed on the master cylinder reservoir cap, and the owner's manual fluids chart lists GM DOT 3 Hydraulic Brake Fluid, GM Part No. 19353126.

That answer is the same in the 2018, 2019 and 2020 owner's manuals. Below is what the spec means, why the five-year change matters, how to check the level correctly, and what to look at while the brakes are apart.

Enclave brake fluid spec at a glance

Buick's manual is specific about the source of the fluid, too: use DOT 3 from a clean, sealed container. A bottle that has been sitting open on a garage shelf has already started pulling moisture out of the air.

Why the five-year flush matters

DOT 3 is a glycol-based fluid, and glycol fluids absorb water. Buick's manual puts it plainly: brake fluid absorbs water over time, which degrades its effectiveness, and it should be replaced at the specified interval to prevent increased stopping distance.

The reason is boiling point. The federal brake fluid standard, FMVSS No. 116, sets minimums for new (dry) fluid and for fluid that has absorbed moisture (wet):

So the minimum a DOT 3 fluid has to meet falls from 401 F when dry to 284 F once it is wet. On a three-row crossover that often carries a full load of passengers or pulls a trailer, a long downhill grade puts real heat into the calipers. If the fluid there boils, it forms vapor bubbles, and vapor compresses where liquid does not. The pedal gets soft and travels further, which is the exact symptom Buick tells owners to take to a dealer: a rapid increase in pedal travel, or a pedal that does not return to normal height.

Moisture also sits in the system and works on the internal metal parts of the calipers, the ABS hydraulic unit and the master cylinder. Changing the fluid on schedule is cheap insurance against replacing those parts later.

Can you use DOT 4 or DOT 5 in an Enclave?

Buick's instruction is to use GM approved DOT 3, and the manual warns that the wrong or contaminated brake fluid could damage the brake system and lead to a loss of braking. Two points are worth knowing:

• DOT 5 is silicone based. FMVSS 116 requires silicone DOT 5 fluid to be dyed purple so it cannot be confused with glycol fluids. It is a different chemistry from the DOT 3 this system was built for. Do not put DOT 5 in an Enclave.
• DOT 4 is also glycol based and carries a higher minimum boiling point, but it is not what Buick specifies for this vehicle. The simplest path is to follow the cap and the manual and use a DOT 3 fluid that meets GM's requirement.

The federal standard also requires every brake fluid container to warn you to keep the fluid clean and dry, store it only in its original container, keep that container tightly closed to prevent it absorbing moisture, and never refill the container or use it for other liquids. Follow those rules and buy small bottles rather than one big one that sits open for a year.

How to check Enclave brake fluid the right way

1. Park on a level surface and put the transmission in P (Park).
2. Find the master cylinder reservoir; the engine compartment overview in the owner's manual shows its location.
3. Read the level against the minimum and maximum marks on the reservoir. It should sit between them.
4. If you need to open the cap, wipe the cap and the area around it clean first so dirt does not fall into the reservoir.

Here is the part many owners get wrong: do not top off the fluid just because it has dropped a little. Buick's manual says there are only two reasons the level goes down. The first is normal lining wear: as the pads wear, the caliper pistons move outward and hold more fluid, so the reservoir level falls. When new pads are installed the pistons are pushed back and the level comes back up. If you topped it off in between, there will be too much fluid once the new pads go in. The second reason is a leak, and adding fluid does not fix a leak.

So a slowly falling level on a vehicle due for pads is normal. A level that drops fast, a wet spot near a wheel, or the brake warning light coming on (the manual says the light comes on when the fluid falls to a low level) means the hydraulic system needs to be inspected now. Be careful with spills as well: brake fluid damages painted surfaces, and Buick warns that overfilled fluid can spill onto a hot engine and burn.

Symptoms that your Enclave needs brake service

• High-pitched squeal while driving that goes away when you press the pedal firmly: that is the built-in pad wear indicator, and the manual says it means new pads are needed.
• Soft or sinking pedal, or more pedal travel than normal: possible air, moisture-laden fluid, or a leak.
• Brake warning light on: low fluid level or a system fault.
• Pulsation in the pedal: Buick notes that properly torqued wheel nuts help prevent brake pulsation, so uneven lug torque after a tire rotation is a common cause, along with worn rotors.
• Flashing PARK light: the Electric Parking Brake is only partially applied or has a problem. Buick says not to drive the vehicle while that light is flashing.

The flush, and what to replace at the same time

A brake fluid replacement means pushing new DOT 3 through every line until clean fluid comes out of each caliper bleeder, not just drawing out the reservoir and refilling it. The reservoir holds only part of the fluid in the system, and the fluid that has taken on the most heat sits out at the calipers. Follow the bleed sequence and procedure in the factory service information. The Enclave's stability and Brake Assist functions work through a hydraulic brake control module, so do not let the reservoir run dry during the job; air in that module makes bleeding much harder.

Because the fluid change and a pad job both involve the calipers, many owners do them together:

• Pads: Buick says pads should be replaced as complete sets. Our 2018-2020 Buick Enclave front ceramic brake pads are listed for this generation, and the full range is under brake pads.
• Rotors: Buick's inspection list calls for checking rotors for surface condition. Scored or pulsating rotors are a good reason to fit new brake rotors with the new pads.
• Hoses and hardware: the same inspection list says to check brake lines and hoses for leaks, cracks and chafing. Cracked flex hoses are a common leak source; see brake hoses and brake hardware kits.

Buick also says to always use new, approved replacement brake parts, because the wrong parts or improperly installed parts can change braking performance. When the wheels go back on, tighten the wheel nuts evenly in the proper sequence to the torque value in the owner's manual.

How hard is the job?

Checking the fluid level is a two-minute job anyone can do. A full flush is a moderate DIY job for someone with a bleeder wrench, clear tubing, a helper or a pressure bleeder, and a sealed bottle of DOT 3. The risks are running the reservoir dry, spilling fluid on paint, and leaving air in the system. If the pedal is not firm and high after the job, do not drive the vehicle; have it bled properly. For most owners, pairing the five-year fluid change with the next pad replacement is the most efficient way to keep an Enclave's brakes in spec.

Frequently Asked Questions

What brake fluid does a 2018-2020 Buick Enclave take?

GM approved DOT 3 brake fluid, as marked on the reservoir cap. The owner's manual lists GM DOT 3 Hydraulic Brake Fluid, GM Part No. 19353126.

How often should I change the brake fluid on my Enclave?

Buick's maintenance schedule says to replace the brake fluid every five years for the 2018, 2019 and 2020 model years.

Why is my Enclave brake fluid level low?

Either the pads are worn, which lowers the level normally, or there is a leak. Do not simply top it off. If the pads are near the end, the level will come back up with new pads; if they are not, have the system checked for a leak.

Can I mix DOT 3 and DOT 5 in my Enclave?

No. DOT 5 is a silicone-based fluid, dyed purple by federal rule, and is a different chemistry from the DOT 3 the Enclave is filled with. Use GM approved DOT 3 only.

Is it OK to use an opened bottle of brake fluid?

Buick says to use fluid from a clean, sealed container. Brake fluid absorbs moisture once opened, which lowers its boiling point.

Should I change the fluid when I replace my brake pads?

If the fluid is near or past its five-year mark, doing both at once saves time, since the calipers are already being serviced.

Sources

1. 2019 Buick Enclave Owner's Manual (GM) - DOT 3 spec on the reservoir cap, sealed container, five-year replacement, level check, do-not-top-off guidance, wear indicators, EPB, inspection list, GM Part No. 19353126
2. 2018 Buick Enclave Owner's Manual (GM) - same DOT 3 spec, five-year interval and GM part number for 2018
3. 2020 Buick Enclave Owner's Manual (GM) - same DOT 3 spec, five-year interval and GM part number for 2020
4. 49 CFR 571.116, FMVSS No. 116 Motor Vehicle Brake Fluids (Cornell LII) - DOT 3/4/5 dry and wet boiling point minimums, purple DOT 5 silicone, container warnings