How To Install An Engine Block Heater

Cold starts are your car’s worst enemies. In cold weather, oil gets thicker and most of the wear on your engine comes from those few minutes between the ignition and the moment where your engine reaches its optimal working temperature. Fortunately, the use of a block heater during winter can ease things up a bit for your engine and help you save a good amount of money at the same time.

A good OEM block heater installed by the dealer doesn’t always come cheap and some of them don’t even offer a block heater option on their vehicles. So what are you supposed to do if you are on a tight budget and your car manufacturer apparently didn’t think about the fact that some of us live where the temperature actually drops below zero in the winter?

Install one by yourself!

How does an engine block heater work?

An engine block heater is a very simple device in essence. No matter how it is originally designed, they all work basically the same. Power goes through an electrical element creating heat and ultimately warming up whatever it’s installed on. Depending on the type, the element can be submerged in coolant and oil or simply installed on the outer of the container in which the liquid it’s supposed to warm up is.

Different block heater models are available depending on the desired result. Whether it’s to warm up the coolant inside your coolant system, the engine oil, the transmission oil or even the petrol and diesel fuel, there’s a block heater for that!

Benefits of a block heater

Starting in cold weather prematurely wears off the engine components. When it’s cold, the engine oil is thicker and does not circulate as well. The engine must then work harder to overcome internal friction. But, thanks to the good old “block-heater”, the engine can start already half warmed-up and its components are then less solicited.

You may have already noticed it before: in cold weather, a warm engine runs smoother than a cold one. Also, because a warmed-up engine runs and burns fuel more efficiently, oil contamination is kept to a minimum, ultimately leading to longer service intervals and lower maintenance costs.

On average, a vehicle equipped with a block heater will save up to 15% of fuel during the first 20km of a drive. And in case you are wondering, hybrid cars are also benefiting from the same 15% fuel saving, even though that added 15% in fuel-efficiency is lower in terms of cost since hybrids typically burn less fuel. The bigger the engine, the bigger the savings. Simple as that!

If your vehicle doesn’t come factory-equipped with a block heater, the purchase of such a device might seem superfluous. But, when distributed over the lifespan of the vehicle, the total cost of a block heater will be all worth it in the end.

Types of block heaters

Most block heaters are installed directly on the engine block, ideally immersed in coolant fluid. This type of block heaters are usually more efficient than other models but they are also a bit harder to install and may require basic auto mechanic knowledge and professional tools while dry heaters, or bolt-on models, are easier to install but are often a lot less efficient. It’s all about finding one that fits your needs as well as your budget and skill level.

In most cases, you should be able to purchase a block heater directly from your auto dealer’s parts department. If your car manufacturer is not offering one, or it’s simply too expensive, most aftermarket auto parts stores will be able to help you find a universal model for your car, usually for a fraction of the dealer’s price.

Freeze plug heaters

Freeze plug heaters are block heaters meant to be installed directly on the engine block, in place of one of the freeze plugs. For those of you who don’t know what a freeze plug is, take a look at the back of your engine and look for round metal cups on the side of each cylinder. These plugs are designed to pop-out if, for some reason, the coolant fluid were to freeze up inside the coolant passages, preventing the engine itself from cracking. This type of block heater is one of the most efficient of them all, it’s definitely not the easiest model to install though.

How to install

First, you’ll need to drain the cooling system. You don’t necessarily need to drain all of it but make sure to drain the radiator, though, or you’ll end up making a mess if the coolant level is not below the freeze plug when you get rid of it.

Most radiators come with a drain plug located near the bottom of the radiator or beside the lower hose. If it’s not the case, simply remove the lower hose clamp and pull the hose to let the coolant out. Remember to place a clean pan under the radiator to collect the coolant so you don’t have to buy new coolant fluid.

Now comes the tricky part.

Removing the freeze plug.

If you bought a block heater specifically designed for your car model, look inside the instruction manual to find which freeze plug to remove. Any freeze plug should do but some are simply 1- easier to remove and 2- easier to correctly place the block heater inside of it.

Once the coolant level is lower than the freeze plug you intend to remove, use a punch and a hammer. Start by gently tapping with the hammer and hit harder and harder until the plug pivots on itself. Watch out not to push the plug inside the engine block. The goal here is to be able to get a grip on the plug to pull and remove it. Once the plug has moved a bit, use a good pair of vise-grip or a pry bar to pry it out of the hole.

After you have removed the plug, clean out any burrs, sharp edges, paint or compound from the machined surface of the hole. Remove the O-ring from the block heater and insert it inside the freeze plug hole. This step is only meant to make sure nothing is interfering with the block heater once in its final position. Once the heater is inserted with the O-ring in place, it will be really complicated to remove without damaging the O-ring.

The heating element shouldn’t touch anything inside the engine block. The instruction manual may require you to place the element in a specific direction so make sure to read the instructions completely before going any further.

Once you are absolutely certain everything is in good working order, mark the position of the block heater and remove it. Re-install the O-ring and lubricate it with silicone grease to ease up the installation process. Re-insert the block heater inside the freeze plug hole and align it correctly.

Most freeze plug heaters are held in place using a butterfly nut. This kind of nut is extremely fragile and surprisingly easy to strip. Always use an accurate 1/4-drive torque wrench and tighten the nut to the correct torque.

When the block heater is correctly set in place, all you need to do is to run the electric cord from the heater connector to the front of the vehicle. Think of where you’d like the male connector of the electric cord to come out of the car first. A common location is to place the connector inside the front grill so you can easily pull it out when needed and push it back inside the grill when it’s not. Another common location is beside the battery or inside the engine bay, near the headlights so you can simply pop the hood, take the connector out, plug it and roll it back in after use.

Always use tie-wraps to correctly secure the electric cord inside the engine bay. Keep the cord away from heat sources like the exhaust manifold to prevent it from melting.

Once everything is ready with the block heater, refill the radiator with coolant, correctly bleed the system and let the car run until the radiator fan starts. Take the car out for a test drive, make sure everything is working great, check out for leaks and if everything’s good… voila!

Drain plug heaters

Drain plug heaters work pretty much the same as freeze plug heaters. The difference lies in the installation process. Drain plug block heaters are, indeed, designed to be installed in place of the engine block’s drain plug instead of the freeze plug and they are usually threaded for that very reason.

How to install

To install a drain plug heater, you first need to drain the coolant inside the engine. You don’t really need to drain the radiator as removing the engine block’s drain plug is obviously required anyway and will lower the coolant level well enough.

Remove the engine block’s drain plug and store it somewhere you’ll remember. You may need it sometime in the future if you ever decide to get rid of your block heater when it starts leaking or stops working and replacement drain plugs are a pain to find in auto parts stores.

Apply some thread seal tape (also called Teflon tape) to the heater’s threads and install it where the drain plug was located. Torque it to the required torque according to the manufacturer and refill the coolant. Check for leaks and, if everything seems fine, you can plug the cord to the heater and run it exactly as you would do for a standard freeze plug heater.

Once it’s done, bleed the coolant system by letting the engine run until it’s absolutely free of air pockets. You could also bleed the coolant before plugging the electrical cord to the heater and run it to the front of the car but I prefer doing that first since it allows you to work on a cold engine. It’s way easier that way and you won’t risk burning your hands on a dangerously hot metal part.

Cartridge heaters

Cartridge heaters are, and by far, the easiest coolant heaters to install. The only drawback is that the engine on your car must have been originally designed to accommodate one.

On some car models, there’s a special metal housing near the coolant chamber, usually on the side of the engine head, where you can slide a cartridge heater and clip it to a bracket. The heater is then sitting right beside one of the coolant passages where it will heat the coolant by thermal conduction.

If your car was designed with a cartridge heater in mind, definitely get one of those. They literally take no more than 15 minutes to install and they work just as fine as any other coolant heater. They tend to be a little more expensive though, you’ll never have to face a freeze plug coolant leak with a cartridge style block heater.

That’s worth every penny.

In-line heaters

In-line heaters are kinda old-school. They were mainly used before cartridge and drain plug heaters were a thing. But they still work as good as ever and if for some reason, you aren’t able to fit a standard block heater model on your car, an in-line heater may be a good option for you.

An in-line heater is, literally, a heater made to be installed “in-line” with the coolant circulatory system. Put simply, it’s a heater you can install wherever you want, typically, you would install it at the output of the radiator or near the thermostat. You simply cut a portion of any coolant hose on your vehicle and connect both sides of the hose to the input and the output of the heater. The coolant will be warmed-up as it passes through the heater.

Oil pan heater

Don’t let the name fool you, oil pan heaters aren’t made only to warm-up oil pans. In fact, these are made out of a plastic pad in which is encased a heating element. You can pretty much stick one of those to any metal surface of your engine and it will heat up whatever is inside. The most common place is, indeed, the engine oil pan but the transmission oil pan is also a good idea.

Pre-heating the tranny’s oil can help with hard shifting in cold weather and will also reduce the overall cold start wear on your transmission’s components.

To install an oil pan heater, start by thoroughly cleaning the area where you want to place it using brake cleaner or any alcohol based cleaner. The surface must be exempt from any grease and dirt. Peel off the backing paper to reveal the sticky side of the heater and place it on the oil pan. To make it totally waterproof, apply a thick layer of silicone gasket maker all around the heater to seal the edges and prevent water and snow from getting inside of it and ruining the whole thing.

Once it’s dry, run the power cord to the front of the car as for any other conventional heater and make sure it’s working correctly using an infrared thermometer.

It’s important to mention that you could use more than one oil pan heater on the same vehicle. For example, you could use one for the tranny oil and one for the engine oil. If you do so, always consider using two independent power chords. If for some reason you only have access to one power cord, always plug both heaters in parallel to keep them working at their full potential. Plugging them in series would result in two heaters working at only 50% of the total power and you would have to plug them way sooner to achieve the same result. That would be kinda counterproductive.

Be aware that stick-on heaters aren’t nearly as effective as other more conventional coolant heaters. Oil takes more time to heat up than coolant and transferring heat from the heater to the oil pan and finally to the oil also takes more kilo joules. On the other hand, they are a lot cheaper, a lot easier to install and you can have a lot more of them.

That’s a lot of good stuff.

Battery Warmer

Another good option in the “heating accessories that aren’t quite a block heater but give similar results” is the battery warmer. They basically work the same as oil pan heaters do and are even easier to install.

Different battery heater models are available. Some of them are designed to be inserted around the battery while others are to be installed beneath the battery, on the battery rack. To install one, simply disconnect your battery and remove it from the car. Depending on the model, either slide the battery warmer over the battery or place it on the battery rack. Re-install the battery, reconnect it like it was before and that’s it!

Engine warming blankets

The last item is definitely the most unusual one but also the most versatile on the list. Engine warming blankets are literally nothing more than heavy duty heating blankets. You simply have to slide one under the hood when you park your car at night and plug it in to keep your engine warm all night long.

They are also the only items that aren’t permanently installed on the vehicle. This feature allows you to share it between more than one car or decide when you want to use it or not.

Engine warming blankets can also be used as warming pads you can lay on the floor if you need to do some mechanical work in an unheated garage or your home’s driveway. They can even be used in pair with a power pack to provide heat while winter camping when placed under a tent or a sleeping bag.

If you want a heater that you can keep and re-install on your next cars or if you don’t want to bother with any installation whatsoever, definitely get yourself a warming blanket right away.

Last words

Keeping cold starts to a minimum is one of the best moves you can do to save on long-term maintenance costs. Your oil will last longer, it will help prevent o-rings and seals leaks, and overall wear and tear will be greatly reduced. For all of you out there, living where winter is harsh and cold, installing a quality block heater is probably your best bet to survive the freezing weather until summer comes around again.

Until then, good luck and don’t despair.

Summer is never that far away…

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