2005-2010 Jeep Commander Brake Fluid Type and Flush Interval

By Core Brake Parts Tech Team — Circleville, OH warehouse

The Jeep Commander takes DOT 3 brake fluid meeting SAE J1703. Jeep's owner's manual calls for Mopar DOT 3 and says DOT 4 is acceptable if DOT 3 is not available. The factory maintenance schedule does not list a brake fluid replacement interval, so the practical answer is to change it on time and condition: test it every couple of years and flush it whenever it tests bad, looks dark, or the hydraulics have been opened up.

What brake fluid the Jeep Commander uses

The Commander (sold in the US as a 2006 through 2010 model and built from 2005) uses a conventional glycol-based hydraulic brake system with disc brakes front and rear, ABS, traction control, Brake Assist and electronic stability control. All of those systems share the same fluid that sits in the master cylinder reservoir under the hood.

The fluids chart in the 2008 Commander owner's manual lists the brake master cylinder as taking Mopar DOT 3 Brake Fluid, SAE J1703, and adds that if DOT 3, SAE J1703 fluid is not available, DOT 4 is acceptable. It also says to use only recommended brake fluids. That spec applies across the 3.7L V6, 4.7L V8 and 5.7L HEMI versions, because the fluid requirement does not change with the engine. Confirm against the cap on your own reservoir, which carries the fluid spec for your year.

DOT 3 vs DOT 4 in a Commander

Both DOT 3 and DOT 4 are glycol-ether fluids, which is why Jeep allows DOT 4 as a substitute. The difference is heat tolerance. Federal Motor Vehicle Safety Standard 116 sets these minimum boiling points:

The wet number is the one that matters on an older Jeep. It is the boiling point after the fluid has picked up moisture, and it is far lower than the dry figure. For a Commander that tows, climbs long grades or sees trail use, a quality DOT 4 gives more margin against a soft pedal after repeated hard stops. For normal daily driving, fresh DOT 3 does the job the system was engineered for.

Do not put DOT 5 silicone in a Commander. It is not on Jeep's approved list and it is a different chemistry from the glycol fluid already in the ABS unit, lines and calipers. The federal standard requires silicone DOT 5 to be dyed purple, while DOT 3 and DOT 4 run colorless to amber, which helps you spot the wrong fluid in a reservoir.

Why the fluid wears out and how often to flush it

Glycol brake fluid absorbs water. That is why the federal standard requires every container to say to keep it tightly closed to prevent absorption of moisture, and why the Commander manual tells you to use only fluid that has been kept in a tightly closed container. Moisture works into the system over the years, and two things happen:

• The boiling point drops toward that wet rating, so heavy braking can boil the fluid in the calipers and the pedal goes soft or sinks.
• Internal corrosion starts. Wagner notes that absorbed moisture can lead to corrosion in the brake lines and brake system, and that it lowers the boiling point and pedal effectiveness.

Because Jeep does not print a flush interval for the Commander, go by time and condition rather than mileage. Wagner's guidance is to change brake fluid based on time elapsed, and to test it if the vehicle works in severe conditions. Their replacement threshold is a copper content of 200 ppm or more, which is what copper-reading brake fluid test strips measure. A reasonable plan for a Commander:

• Test the fluid every two years, or at every brake job.
• Flush when the strip shows high copper, when the fluid is dark brown instead of clear to amber, or when you replace a caliper, hose or master cylinder.
• Test more often if you tow, drive in the mountains, or take the Jeep off road through water crossings.

Every Commander on the road is now well over fifteen years old. If you have no record of a fluid change, assume it has never been done and flush it.

Checking and topping off the reservoir the right way

Jeep lists the brake master cylinder level as a monthly check. The owner's manual procedure is simple, and the warnings in it are worth following:

1. Clean the top of the master cylinder area before removing the cap so dirt does not fall in.
2. Fill only to the level marked on the reservoir. Jeep warns that overfilling can spill brake fluid on hot engine parts, where it can catch fire.
3. Use fluid from a tightly sealed container. An open bottle on a shelf has already been absorbing water.
4. Keep petroleum products away from it. The manual cautions that petroleum-based fluid contaminating the brake fluid will damage the seals.

A level that drops slowly over tens of thousands of miles is normal: as the pads wear, the caliper pistons move out and hold more fluid. Jeep points out that a low level can also mean a leak. If the level drops quickly, or the red BRAKE warning lamp comes on, check the pads first, then look for wetness at each caliper, the flexible hoses and the master cylinder. The manual also says to inspect the brake hoses and lines at every oil change and replace any hose that shows cracking, scuffing or worn spots.

Flushing the Commander's brakes, and what to replace at the same time

A flush is a bleed that keeps going until clean fluid comes out of every bleeder. On a four-wheel-disc Commander with ABS, the usual approach is to start at the wheel farthest from the master cylinder and work toward the closest one, never letting the reservoir run dry so no air gets drawn into the ABS unit. If air does get into the ABS hydraulic unit, the factory procedure uses a scan tool to cycle the valves while bleeding, so follow the service manual or let a shop with that tool do it. Tighten bleeder screws to the value in the factory service manual; they are small and snap easily if forced.

The fluid change is a good time to deal with anything else in the hydraulic system, since you will be bleeding it anyway:

• Pads. For the front, the EBC Greenstuff 6000 front brake pad set for the 2005-2010 Commander is built for heavy SUVs and trucks. For the rear, the EBC Extra Duty rear brake pad set for the Commander suits towing and heavier use. More options are in our brake pad collection.
• Rotors. If the rear rotors are grooved, lipped or below minimum thickness, the EBC 3GD slotted rear rotor set for the Commander pairs with the pads above. See all brake rotors.
• Hoses and hardware. Replace any hose that is cracked or swollen, and fit new clips and pins while the calipers are apart. See our brake hoses and brake hardware kits.
• Calipers. A sticking caliper often traces back to corrosion from old, wet fluid. Replacements are in brake calipers.

How hard is it? A basic two-person pedal bleed is a driveway job for someone comfortable with jack stands and a line wrench, and it usually takes about an hour. Buy more fluid than you think you need, in sealed bottles, because a full flush pushes old fluid out of all four corners. The job only gets harder if a bleeder is seized or the ABS unit needs a scan-tool bleed.

Frequently Asked Questions

What type of brake fluid does a Jeep Commander take?

DOT 3 brake fluid that meets SAE J1703. Jeep specifies Mopar DOT 3 and allows DOT 4 when DOT 3 is not available. The requirement is the same for the 3.7L, 4.7L and 5.7L models.

Can I use DOT 4 in my Commander?

Yes. Jeep's owner's manual lists DOT 4 as acceptable. It has higher minimum boiling points than DOT 3 under the federal standard, which makes it a sensible choice if you tow or drive long grades.

Can I mix DOT 3 and DOT 4?

Both are glycol-based and Jeep approves both for this system, so topping off with DOT 4 is fine. The blend will perform closer to the lower-rated fluid, so a full flush is the way to get the full benefit of DOT 4.

How often should I flush the brake fluid on a Commander?

Jeep does not publish a flush interval for it. Test the fluid every two years or at each brake job, and flush when it tests high for copper, looks dark, or any hydraulic part has been replaced. On a Commander with no service history, flush it now.

Why does my Commander brake pedal feel soft after a long downhill?

Old fluid that has absorbed moisture can boil in the calipers under sustained braking, which creates vapor and a soft pedal. Let the brakes cool, then have the fluid tested and replaced, and check the pads and rotors for heat damage.

Sources

1. 2008 Jeep Commander Owner's Manual - Mopar DOT 3 SAE J1703 spec, DOT 4 alternate, level check procedure and warnings, maintenance schedule items
2. 49 CFR 571.116, FMVSS 116 Motor Vehicle Brake Fluids (Cornell LII) - DOT 3, DOT 4 and DOT 5 dry and wet boiling points, container moisture statement, fluid color requirements
3. Wagner Brake: When to Change Brake Fluid - moisture absorption and corrosion, time-based changes, 200 ppm copper replacement threshold