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How To Diagnose an Overheating Jeep

Posted in How To: Engine on June 18, 2015
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Photographers: Brian Lienhop

Overheating and four wheeling seem to go hand and hand. Increased strain from larger tires, heavy aftermarket equipment, and traversing grueling terrain at low speeds all play a part in turning up the heat. Preventing your Jeep from overheating is usually much easier (and cheaper) than you might realize. Here, we’ve put together a series of tips, tricks, and things we’ve learned over the years to reduce the likelihood of our Jeeps boiling over.

Clear a Path

A winch, front bumper, and even auxiliary lights are common place in the off-road world. Just as diverse as the array of aftermarket options will be the effects on your Jeep. When you block-off large sections of your front end, you are inhibiting air flow to your radiator. In rigs equipped with air conditioning and transmission coolers, you are also reducing the ability of those features to perform optimally. Removing or modifying the location of your auxiliary lights or winch can make a big difference. In addition, switching the type of bumper you have will also play a part.


When it comes to modern Jeeps, electric fans are the mainstay. Electric fans are easier to package, lighter, and don’t rob power in comparison to a more traditional belt-driven fan. When electric fans have problems, you can typically chase it down to small electric issue or burnt motor. We’ve seen guys swap out belt-driven (also known as mechanical) fans for electric fans over the years in hopes of freeing up horsepower. While they will do just that, we prefer the reliability of a mechanical fan in most applications. If you think your mechanical fan isn’t performing as it should, chances are the fan clutch is shot. Removing the clutch fan often requires a special tool but is a straightforward job overall.

Radiant Flow

A leaky, clogged, or damaged radiator is often the culprit for an overheating rig. Being packed with mud is also high on the list of things that will make your radiator less effective. More often than not, unless you are turning up the power under the hood or have swapped in a heat-thumping V-8, your stock radiator is likely more than fine for your Jeep. Sure, aluminum radiators are significantly more durable than the plastic-capped ones you’ll find under the hood today, but it’s more for the performance-oriented crowd. Aluminum radiators gained popularity years ago due to their weight-savings (they can be up to 15 pounds lighter) and increased volume it can flow due to larger internal tubing. Don’t immediately assume that a different radiator will cure your heating woes as there is more to the system.

Shrouded with Problems

Most fan shrouds are plastic and become brittle with age. A cracked or missing panel might not seem like a big issue, but it can be a source for your overheating trouble. Even with larger fans and radiators, a fan shroud should be used to properly channel the air and increase the effectiveness of the fan.

Hose & Housing Years ago

Swapping in a low-temp thermostat could reduce overheating woes. These days, engines are designed to perform at optimum temperature ranges. Lowering the thermostat could actually hurt more than help on modern engines. Thermostat housings, thermostats, and your cooling hoses are known failure points on high-mileage engines. One of the most common trouble spots are the stock hose clamps. These are designed to expand and contract with the hose. Over time, they wear out and can allow the hose to leak and, in some cases, allow the hose to become uncoupled from the radiator or engine. An inexpensive solution is to replace the tension clamps with worm clamps, which you can pick up at your local auto parts store.

Plug it Up

Freeze plugs are one of the most overlooked common sources for overheating. When the plugs themselves fail, it’s usually the result of a pin-hole leak that is often hard to see as traces of fluid can evaporate quickly. If you are replacing one, it’s a good idea to check out the condition of the other(s). While you are there, be sure to clean out your water jacket, as sludge can build up over time.

Even More Fan-tastic

Adding additional cooling fans is another way to help curb heat. Companies such as Flex-a-lite ( offer pusher fans, which are designed to mount in front of the radiator and push air through. These can be helpful for low speed conditions, when the traditional puller or belt-driven fan puller fan isn’t enough.

Oil Coolers

Separating your oil coolers from your radiator will help reduce heating soaking, but mounting the separate coolers in front of the radiator isn’t always ideal on a trail rig. Many aftermarket oil coolers can be purchased with an electric fan assembly attached. This allows you to come up with more creative mounting solutions that won’t occlude cooler air from making to your radiator.

Aqua Movers

Water pumps are a common cooling system fail point. Typically, bearings wear and the pump begins to leak. In many instances, a high-flow pump can be swapped in, which can increase the efficiency of the cooling system.

Louver Love

We all know that heat rises and your hood is a great blanket to keep it in at low speeds. Hood louvers are nothing new in the automotive world, but they are becoming increasingly popular in the off-road sector. At low speeds, we can attest that louvers can be very helpful in expelling underhood temps. Louver kits, such as this one from Poison Spyder Customs (, draw out more air than smaller louver kits, but even smaller sets can be very effective.

Less is Cool

You’ll never get a breeze just by opening one door. Air needs a path to travel, and at low speeds, it often doesn’t have a lot of options. Ditching your inner fenderwells can make a difference in expelling heat as it provides a path for the air to escape.

Napoleon Blown-a-part

Sometimes, your cooling issues run much deeper than you may realize. A blown head gasket can be the result of and contributing factor in an overheating Jeep. If your rig is blowing white smoke from the exhaust or coolant appears to have oil mixed in, these are signs of a head issue. Sometimes, it’s just a simple fix with a gasket, but it’s possible the rig might have a warped or cracked head or even a cracked block.

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