12 Ways To Prepare Your Diesel For Winter

Proper vehicle preparation and maintenance can ensure your truck survives the low temperatures of winter. We put together a list of 12 items you can complete to give you peace of mind as the temperatures drop. We recommend starting this list around October if you’re in the Northern Hemisphere and May if you’re south of the equator. Follow this checklist to make sure you’re ready for the season ahead.


1. Test Your Battery

If possible, have your battery tested prior to the cold weather snap. If your battery tests poorly or is teetering on the acceptable vs. bad line, you should consider replacing it. This preventive maintenance could save you from missing a day at work or being stranded after a no-start.

So why does this happen in winter?

Your battery uses chemical reactions within it to generate electrons. Even when your battery isn’t connected to your terminals, this chemical reaction is still happening which is why some batteries will die if they’re left in storage for too long. When the temperature of the battery is lowered, this chemical reaction slows down, which results in less current output. WAMP, WAMP! This is why battery failures commonly occur just as the ambient temperature begins to drop.

At freezing temperature, battery capacity can be reduced by up to 20%! Your battery system also experiences more load in the winter because the oil in your engine thickens as the temperature drops resulting in your engine producing more resistance too.

Fun fact: a charged battery with proper electrolyte mixture will not freeze, but a dead battery will. Once a battery freezes internally, it is typically not salvageable. A sign of this is the sides of the battery appear bulged out or swollen.

The most accurate way to test your battery is with a Battery Load Tester, but you don’t necessarily need to shell out for one of these, most auto shops offer free battery testing.


2. Check your Belts, Boots, and Hoses

It’s a good idea in general to regularly check your engine components but doing so specifically before winter eliminates emergency repairs. Wear and tear on your rubber engine components can easily turn into awful times waiting for road-side assistance in the bitter cold. When rubber gets cold, it becomes brittle, and can easily crack so we recommend looking at your belts, boots and hoses.

Take a look at your belt(s) with the vehicle turned off to check the rubber for any cracking, especially at areas where the belt turns over a pulley. Also, pay close attention to the edges of the belt for any torn strands. If you see any evidence of this wear, it is highly recommended that you replace the belt. Belt replacement is normally a quick process, so you don’t need to set aside a full weekend for the job.

Check all lines for cracking and check to see if the texture of the material is soft and flexible. The hose or boot should be slightly spongy and should return to its original shape after being squeezed. Check all connections for seeping or leaking, and address these with new clamps, hoses, or boots as necessary. Some modern systems use plastic quick disconnects that utilize O-rings for sealing. If a connection is leaking, replace the O-ring or the entire part if needed. If you have any doubts about a line, hose, or boot, it would be wise to replace that component before it becomes a problem down the road. You can always take this opportunity to upgrade to silicone. We offer replacement silicone radiator hose kits for a variety of trucks, including FordGMJeep and RAM. We also offer silicone intercooler pipe boot kits with our DuraCore™ technology for greater resistance to oil and fuel that may be present in the charge air cooling system. If you want a radiator hose or intercooler pipe boot that will last, go with a silicone replacement product, and you will not be disappointed. As with all Mishimoto products, our silicone coolant hose kits include our signature Lifetime Warranty.


3. Test and Change your Coolant

When coolant freezes, serious damage can happen to your engine. Your engine is designed with numerous press-fit plugs (freeze plugs) that are made to rupture if the internal fluid freezes. If a plug ruptures, you will be treated to a leaking coolant system, and that’s a best-case scenario! If a plug does not function, freezing water will cause damage to the engine block and cylinder liners, and the remedy for that is an engine replacement.

Make sure to check your cooling system to ensure that it has the correct mixture of antifreeze and water for your vehicle and if the coolant has not been changed in years, it’s a good time to flush it because it can be heavily saturated with sediment and particulates, reducing its cooling efficiency.  Once you’ve replaced your coolant, you can prevent your system from future contamination with a coolant filtration kit. We offer direct-fit options for trucks and Jeeps.

Vehicles require a 50/50 mix of water and antifreeze for proper cooling, protection of internal passages and components, and protection against fluid freezing. You can use a coolant tester to determine the ratio of your current coolant or you can replace your coolant depending on the winter predicted. While you are testing your coolant for proper mixture ratio, take this opportunity to inspect the core and end tanks of the radiator for any leaks.


4. Inspect and Boil? your Thermostat

The basic function of a thermostat is to regulate coolant temperatures. As coolant warms up, your thermostat will begin to open and allow fluid to circulate through the radiator. Once the engine is up to operating temperature, the thermostat should be completely open to allow fluid flow throughout the entire cooling system.

Thermostat failure can happen in the opened and closed positions. If the thermostat fails while open, your truck will take a long time to warm up because coolant will be constantly circulating through the system. Although this is unlikely to cause any engine damage, you’ll see a check-engine light (CEL). You also won’t have proper cabin heat, until long after the truck has been running. BRRRRR!

Freezing Sesame Street GIF by Willem Dafriend

A thermostat that fails in the closed position will not allow coolant to flow through the system resulting in overheating. This situation can be extremely harmful and lead to engine damage or a blown head gasket if not identified quickly.

If your thermostat has failed, you’ll know it, but if you want to inspect for yourself, here are a few ways to test your thermostat. Once your vehicle is warm, you can check the temperature of your radiator hoses. Use gloves to touch the upper and lower radiator hoses to ensure they are both warm. If one is cold, the thermostat might not be opening, but if the thermostat is stuck closed, you will feel extra hot hoses.

Another way to test if your thermostat is functioning properly, is by placing your thermostat in a pot of boiling water. Before you even place it in the pot, check to see if your thermostat is stuck open (needs replacing if so) and inspect the rubber sealing materials to make sure they aren’t damaged. Once you’ve done this initial check, add your thermostat to the pot of boiling water, give it a quick stir and watch to see if it opens. Just like if you were boiling clams and mussels, if it doesn’t open, chuck it.

Thermostat boiling water test
We commonly recommend higher-temperature thermostats for diesel trucks that spend time in colder climates to improve efficiency and performance.

Age plays a role in the wear and tear on your thermostat. Keep in mind that this component is in direct contact with engine coolant, and it frequently experiences substantial temperature fluctuations. If you have a lot of mileage on your truck and the thermostat has never been replaced, consider doing so before winter. If you need to replace your thermostat or want an upgrade, we offer high/low-temperature thermostats for a wide range of Ford PowerstrokeDodge Cummins, and Chevy/GM Duramax engines.


5. Glow Plugs and Grid Heaters

A glow plug functions to heat the combustion chamber for cold starts. The plug threads into the cylinder head, and then the tip is inserted into the combustion or pre-combustion chamber. Once energized, the plug heats up to more than 1880°F (1000°C), to kick-start your diesel engine cold-start.

You won’t usually know if a glow plug has failed when the weather is warm, but once temperatures drop, your truck will be difficult to start, or not start at all. The usual failure of a glow plug involves damage to the heating rod that is exposed to extremely high temperatures during combustion. An overheated rod can melt and degrade over time and is also susceptible to carbon deposits. Additionally, if a glow plug tip swells, it can become almost impossible to remove from the cylinder head, leading to a big repair bill. Be sure to use high-quality components that meet or exceed the OEM specification.

Testing your glow plugs can seem intimidating, especially since you will have six to eight plugs, but it’s really not that bad. One of the best ways to test glow plugs is by using a testing device made specifically for these plugs. This device provides an accurate answer whether you will need to replace one or more plugs. Additionally, this device normally operates with the plugs still installed in the engine, saving a ton of time. The only downside is the cost; a good unit comes in around $150–$200. If you don’t want to shell out for this tester, our original blog post has a way to test your glow plugs if you don’t mind putting in some extra effort.

There is another… A grid heater or intake heater is also used to prevent no-starts during winter. This is a heating coil found in the intake or near the engine that warms up incoming air going to the engine, performing the same function as a glow plug. Checking the resistance of these heaters and comparing them with factory specifications is the best way to ensure proper operation before winter. Unlike glow plugs, engines typically only have one intake heater that serves all the cylinders.


6. Swap your oil

As we mentioned with battery maintenance, oil thickens in the cold creating greater resistance to engine operation and makes starting tough. Cold oil has difficulty quickly circulating through passages and galleys to lubricate the proper engine components so to alleviate this issue, the goal is to increase the flow of oil when cold to eliminate dry-running engine wear or your vehicle.  

Although all vehicles will differ, many recommend switching to 5W-40 during the winter months. Check your owner’s manual before making this switch. This oil weight will provide greater flow during cold temperatures compared to 15W-40, yet it will retain the same properties once warmed. If you are in an extremely cold climate, 0W-40 is usually recommended.

By switching to a more “winter friendly” oil, you can reduce wear on your starter, battery, and injection system. We recommend considering this if you are nearing an oil change or anticipating a service interval occurring during the winter months.

Also, it’s important to note that during winter, and especially on boosted applications, oil blow-by can be way more severe. Check out our article on the harmful effects of Blow-by here for more information. A catch can helps to alleviate the build-up of carbon deposits on your valves and we offer a wide variety of direct-fit options for trucks. You can check them out here and see if this is an upgrade you can make before winter hits.


7. It washes the salt from the undercarriage or else it gets the hose again

Washing under truck

During the winter season, we recommend getting regular undercarriage washes. When big snowstorms are on their way, roads are lined with salt that is great for preventing roads from re-freezing, but terrible for the long-term life of your truck. Salt speeds up the corrosion process and can affect exposed metal surfaces. Most modern trucks feature some form of underside coating, but your truck is still susceptible to rust issues, especially if the underside coating becomes damaged or compromised. Try to get an undercarriage wash after each major snowstorm.


8. Prevent Filter Gelling

Diesel fuel contains paraffins that have a high freezing temperature that can cause a “gelling” of your fuel, making it a solid material. Gelling can result in a clogged fuel filter, clogged lines, and likely an engine shut-down situation. Additionally, diesel fuel systems are susceptible to water and moisture buildup that can freeze, clogging the lines and the filter. To help prevent this from happening, there are a few steps you can take.

Dry Your System

Before winter arrives, ensure that all water has been removed from your fuel system. Several additives are available that utilize isopropanol to remove existing water and several companies offer separator kits that are easy to install and work well. These products are normally inexpensive, so treating your system is recommended.

Change Your Fuel Filter

A dirty fuel filter will clog much quicker than a clean one. If you have not serviced this filter in some time, you should replace it before the winter season.

Use a Winter Additive

For additional protection, you can treat your fuel tanks with additives that prevent both water and wax issues. These additives are inexpensive and certainly worth the small investment.


9. Tread lightly, these jokes are getting Tired

Tires have an impact on grip, ride quality, braking, and of course safety so make sure to check yours while making these inspections. First, you will want to perform a basic inspection of the integrity of your tires, starting with the tread. Make sure that your tread is not worn past safety regulations. If they’re bald, it’s a no-brainer that you should replace your tires, but if they are right on the cusp of being too worn, consider replacing them instead of risking the season.

While you’re looking at your tread, also look for any debris lodged in the rubber itself that could cause a leak. You may be able to patch these holes.

Once you have determined your treads are in good enough condition to last the winter, inspect the sidewalls of your tires for any cuts, bubbles, gashes, or damage. The sidewall is normally not repairable, so if there is a nail or anything penetrating this portion, the tire will need to be replaced. Additionally, a bubble in the sidewall indicates a failure of the internal liner and each of these failures create a tire that is more prone to a blowout or air leaks.

Age is another important factor to consider even if your tires pass all these tests. Tires will be more prone to aging if they are not used, for instance if a vehicle sits for a long period of time. Typical tire compound life extends from 6–10 years, depending upon storage conditions. Chemical reactions within the tire compound will degrade the rubber, resulting in reduced grip and an increased chance of failure.

For those facing extreme winters or planning to tow anything, an upgrade to snow tires will provide a huge difference in grip and vehicle control. If you are expecting only a small snowstorm or two, you can likely press on with all-season tires, assuming you take it slowly and drive in a respectable manner.

Truck driving in a respectable manner

10. Look At Your Windshield – Is it busted?

Cracked windshield BUMMER MAN

Before winter hits you’ll want to make sure your view isn’t obstructed with cracks that compromise the integrity of your windshield. Your windshield is an easy item to check, with the obvious check being to see if you have a huge crack running across your view. If not – that’s great! Where it gets tougher is checking for tiny cracks and chips that could lead to that big crack. These tiny nicks are tiny and hard to see, but they only need a quick change in temperature to spread. We’re sure you can imagine a cold winter day where you blast your defrosters to get warm, this is exactly when that crack will spread and ruin your day.

scared steven spielberg GIF
The moment you blast the heat and that tiny crack makes itself known.

To find the tiny cracks, you’ll need to clear your windshield of dirt and debris and look closely. Sorry, no fancy tricks here! If you do find a small crack, this damage can be easily repaired with an at-home kit and is usually covered by insurance if you want professionals to handle the task. Anything larger than a dollar bill is going to cost you a whole new piece of glass so it’s best to spot these early on.

While you’re looking at your windshield, check your wiper blades to see that they’re in good condition. Rough looking blades don’t clean snow slush that well… The replacement cost will range from $12-$30, so it’s an inexpensive switch. Also, something to consider, any time you find cracks in your windshield, it’s recommended to switch your blades in case glass fragments are stuck in the rubber.


11. Go the Extra Mile

These two upgrades can make life so much easier in the winter.

A block heater functions to keep the engine block and coolant warm during overnight parking, so when you are ready to drive, your truck is already warmed up. This makes starting easier and reduces fuel consumption associated with cold starts. Just plug your block heater in a few hours before you start your truck. Block heaters are relatively inexpensive and normally pay for themselves in the form of comfort and convenience. Just make sure that if you are using an extension cord to reach your truck, that you use one that is rated for the wattage your heater requires and check your heater’s wiring to be sure you won’t cause a fire.

grille cover is also a great way to rapidly warm your truck to operating temperature and keep temperatures from over-cooling during idle conditions. If your truck is struggling to keep warm, a grille cover is an inexpensive way to block airflow and improve interior heat capability.


12. First Aid and Emergency Kit

While this list will help limit the failures you could experience during winter, it will not eliminate all possibilities, so we recommend outfitting your truck with some emergency supplies. This is especially important if you are traveling through extreme terrain or remote areas. Many people toss a bag of items in their backseat for year-round use; however, your kit should include items you will need in a cold-weather emergency. Below is a list of items you should consider stocking for emergency situations. You can get pre-made kits that contain a majority of these necessities, or you can piece it together with what you own currently and make additions when needed.

  • Small shovel
  • Windshield scraper and small broom
  • Flashlight with extra batteries
  • Several water bottles
  • Snack food (energy bars, raisins, nuts, candy bars)
  • Waterproof matches and small candles
  • Extra hats, socks, and gloves
  • First-aid kit
  • Small knife
  • Any medications you normally take (small portion)
  • Blankets or sleeping bag
  • Tow chain or rope
  • Small bag of cat litter (for wheel traction in case you become stuck)
  • Jumper cables or a portable jump starter
  • Emergency flares

Thank you for reading this post! For a more in-depth look at winterizing your diesel, check out our original article here. To shop the full line of Mishimoto Automotive products click here.

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