How to Check and Add Coolant in a Chrysler 300 (2011–2023 Models)

Last Updated on 2025-09-07

Welcome to a tutorial where simplicity greets sophistication under the hood. Today we’re slipping under the skin of the 2015 Chrysler 300 powered by the 3.6L Pentastar, zeroing in on a task that rolls to the bottom of many to-do lists but shouldn’t: adding and checking engine coolant.

At first glance, it looks routine, but don’t be lulled. A coolant lapse is quite sabotage. Low levels, the wrong mix, or leaks sneak past the visible gauges and chip away at the engine’s core health. What we’re doing here is more than a leisurely splash of green fluid; it’s the shield that keeps heat at bay, fights corrosion, and sidesteps that ominous “check engine” ding, along with the repair bills that follow it.

Why Coolant Matters, And Why People Ignore It

In the symphony of routine automotive care, the coolant rarely gets a solo. We scan the dipstick religiously, check the tire wear, and listen for that telltale brake chirp, yet the stout little liquid that lines up behind the engine gets a glance only when it’s visibly low. Coolant is the engine’s unobtrusive protector, sipping up excess heat and ferrying it to the radiator, while simultaneously warding off rust and keeping rubber hoses flexible. It’s a thankless job, done quietly, until the moment the needles start to climb.

The irony, however, is that most car owners can’t tell you what color, or even what formula, is lurking in the reservoir. They march into the parts store, point at the first jug with a low price, and tip it in like it’s washer fluid. This minor lapse can trigger a major meltdown, especially in Chrysler’s all-aluminum trim like the popular 3.6L V6. That engine’s metallurgy is fussy, and the coolant chemistry must match the manufacturer’s recipe. One stray ingredient, and you risk rotting out the radiator, overworking the water pump, or acquiring a chunky, flow-stopping sludge. What started as a cheap, quick fix can snowball into an engine-out repair, reminding us that even the quietest protector deserves respect.

Locating Your Engine Coolant Reservoir

Your Chrysler 300 keeps it simple. Lift the hood, glance toward the left (driver’s) side, and mid-bay, you’ll find a clear, plastic reservoir. That’s where it all starts. The tank sports “LOW” and “FULL” molded lines so you can measure at a glance. When the engine is cold, you want the coolant to be right at or just below the “FULL” mark.

If you can’t quite see the level, use your phone’s flashlight. A quick beam from behind or underneath the tank cuts through the haze, letting you see the fluid through the plastic.

Listen: a low level isn’t a small issue. It’s either leaking, evaporating, or the system wasn’t cared for. A single top-off is okay, but if you find yourself doing it again and again, park it and find the leak.

Adding Coolant: A Step-by-Step Guide

First, give the engine a full chance to cool down. Releasing the cap on a heated coolant reservoir risks a powerful spray of steam and liquid, and the burns can be serious. Let the entire engine bay chill for at least an hour and confirm that every surface feels cool.

When it’s finally safe, loosen the cap a quarter turn, then stand back. A gentle hiss may escape; that’s the escape of trapped pressure and nothing to worry over. Peer into the reservoir itself. If the liquid is bright, clean, and clear, it’s okay. But if it’s muddy, slick, or that unsettling rusty brown, the cooling system is infected and will need a full flush, not a quick top-off.

You’ll need:

Coolant that matches Chrysler’s specifications (usually OAT-type, like Mopar 10-Year/150,000 Mile coolant)
Distilled water (if mixing manually)
A funnel for easier pouring

Two Options for Adding Coolant:

Pre-mixed coolant: Already diluted 50/50 with distilled water — just pour and go.
Concentrate coolant: Must be mixed manually with distilled water in a 1:1 ratio.

Skip the ordinary tap water. The minerals in it can settle inside the radiator and heater core, slowly choking the flow and sapping heat transfer. Picture putting hard water in a coffee maker: the element will eventually stage a quiet revolt and coat everything with white fur.

Fill it up slowly and keep an eye on the gauge. Wait until the liquid creeps to the “FULL” line, then quit. A little excess coolant can sneak past the overflow; push it out when the engine warms and the system can’t keep the balance.

The Danger of Low Coolant

Rolling the dice on low coolant is never wise. One minute you’re cruising the block without a hitch; the next, you’re staring at a cracked head gasket or a seized motor. No coolant means no pressure; no pressure means the liquid stops moving the way it’s supposed, and it’s too easy for the boiling point to be breached. The result is pockets of blistering heat that the radiator can’t find, and the internals pay the price.

That’s why popping the hood and eyeballing the overflow, at least once a month, should feel as automatic as topping off the tank. It’s non-negotiable before any extended trip or the first muggy Saturday of summer. The thirty seconds the check takes can save you entire paychecks.

Choosing the Right Coolant

This isn’t just about the color. Although Chrysler’s OAT coolant usually runs pink or orange, the color alone won’t tell you anything. The crucial factor is the chemical makeup. Chrysler 300s need Organic Acid Technology (OAT) coolant, formulated to safeguard aluminum parts and rubber seals scattered through the engine compartment.

Pouring in the wrong kind, mixing OAT with HOAT (Hybrid OAT) or IAT (Inorganic Additive Technology), sets the stage for gelling, corrosion, and faster component failure.

When in doubt, double-check the owner’s manual or ask a Chrysler service tech. Five minutes spent confirming the right coolant beats five hours spent replacing ruined engine parts.

Perfecting the Mix

Stay rigidly with a mixture of 50 percent coolant and 50 percent water; straying from this formula sabotages the cooling system’s ability to safeguard the engine, the very reason we undertake this work. This exact ratio permits the coolant to extract heat from the engine block and release it through the radiator, while also guarding against freezing in winter and vaporization in summer. Also, the water you add must be distilled; municipal and well water alike harbor minerals that settle in radiator passages, leading to costly blockages.

Next, consult your Chrysler 300’s owner’s manual to confirm the correct coolant chemistry. The recommended fluid contains a blend of antifreeze, corrosion inhibitors, and buffering agents engineered to shield the engine’s aluminum surfaces and to seal plastic and rubber joints in the cooling circuit.

Today's coolants promise extended intervals, which crisply reduce how often you drain and replace the fluid. Nevertheless, you must select the exact formulation specified, as adding the wrong one, or mixing in an off-brand or supplemental coolant, triggers chemical reactions that roughen metal, deplete additives, and ultimately shorten the entire system’s life.

What If the Level Keeps Dropping?

If you notice a gradual loss of coolant over time, that’s not normal. Common causes include:

Radiator cap failure
Hose cracks or pinhole leaks
Leaking water pump
Bad heater core
Internal engine issues (like a blown head gasket)

In these cases, topping off is only a temporary fix. The real solution lies in identifying and addressing the root problem. Otherwise, the system will eventually fail under pressure.

Coolant Flushes: The Forgotten Hero

No amount of quality coolant is permanent. After years of heat cycles, the protective additives disintegrate and leave bare metal vulnerable. Chrysler therefore advises a thorough coolant change every decade or every 150,000 miles, whichever milestone arrives first.

Performing the procedure the right way means draining the dirty fluid, running distilled water or a dedicated flush through the system, and topping off with new fluid. If you’re doing the job in your garage, remember to bleed the system when you’re done. Any air trapped in the hoses and engine can lead to surprising temperature spikes and, in the worst cases, a blown head gasket.