2021 Jeep Gladiator Coolant Capacity, Type, and Maintenance Guide

The 2021 Jeep Gladiator holds between 11.2 and 13.4 quarts (10.6 to 12.7 liters) of coolant, depending on your specific engine and factory towing package configuration. As an ASE-certified master technician, I regularly service the Jeep JT platform, and understanding the unique cooling requirements of these modern off-roaders is critical to preventing overheating on the trail or the highway.

Quick answer

If you are looking for the basic specifications to top off or flush your Gladiator's cooling system, here is what you need to know:

• Total Cooling System Capacity: 11.2 to 13.4 quarts (10.6 - 12.7 L)
• OEM Coolant Spec: Mopar 10-Year/150,000-Mile Formula OAT (Organic Additive Technology). The specific Mopar standard is MS-12106. It is distinctively purple in color. Do not mix this with the older orange Mopar HOAT coolant.
• Mix Ratio: 50/50 blend of concentrated coolant and distilled water (or a pre-mixed 50/50 OAT coolant meeting MS-12106).

Capacity by engine option

The 2021 Jeep Gladiator comes with a couple of engine options, and your capacity will vary slightly depending on which powertrain you have, as well as if you have the Max Tow package which features an upgraded cooling system.

Note: Always buy an extra gallon of 50/50 mix to account for spillage, bleeding, and future top-offs.

Flush interval

Keeping your coolant fresh is vital for protecting the aluminum components in your engine and heater core.

• Normal Duty: Jeep recommends a coolant flush every 10 years or 150,000 miles, whichever comes first.
• Severe Duty: If you frequently tow heavy loads, off-road in hot climates, or idle for extended periods, I strongly recommend changing the coolant every 5 years or 100,000 miles. The corrosion inhibitors in OAT coolant degrade faster under extreme thermal stress.

How to refill & bleed

The 3.6L Pentastar V6 is notorious for trapping air in the cooling system, which can lead to overheating or a lack of heat in the cabin. Here is the best way to tackle it:

1. Drain the system: Locate the radiator drain petcock on the lower passenger side of the radiator. Drain the old fluid into a safe catch pan.
2. Vacuum Fill (Highly Recommended): The absolute best way to refill a modern Jeep is using a pneumatic vacuum coolant filler. This tool draws a vacuum on the entire system and sucks the new coolant in, entirely eliminating air pockets.
3. Manual Bleed Method: If you don't have a vacuum filler, slowly pour the 50/50 mix into the radiator. Locate the small bleeder screw on the thermostat housing (top of the engine, where the upper radiator hose connects). Open this screw slightly while filling until a steady stream of fluid escapes, then tighten it.
4. Warm Up: Leave the radiator cap off, start the engine, and turn the cabin heater to the maximum setting. Let the engine reach operating temperature until the thermostat opens.
5. Burp the System: Squeeze the upper radiator hose carefully to force out remaining air bubbles. Top off the radiator and the overflow reservoir as the level drops. Replace the cap once the level stabilizes.

Common cooling system issues

For the JT Gladiator (and its JL Wrangler sibling), there are a few cooling system quirks you should keep an eye out for:

• Radiator Seam Leaks: The factory radiators have plastic side tanks crimped to an aluminum core. Over time, flexing from off-roading or thermal cycling can cause pinhole leaks along these crimped seams. Look for crusty purple residue along the sides of the radiator.
• Thermostat Housing Cracks: The 3.6L utilizes a plastic thermostat housing that can become brittle and crack, leading to a slow coolant weep.
• Water Pump Weepage: While generally reliable, the Pentastar water pump can occasionally develop a leak at the weep hole as the internal seal wears out, usually starting around the 60,000 to 80,000-mile mark.

If you aren't comfortable performing a vacuum fill or suspect your Gladiator has a cooling system leak, don't risk overheating your engine. Find a trusted shop on Repairius.