Can A Truck Run Without A Thermostat?


Trucks are a durable investment that seem to last forever. However, some truck owners find themselves going through numerous thermostat replacements and consider running their trucks without thermostats altogether.

Can A Truck Run Without A Thermostat?

While you can run your truck without any thermostats, it will not run at an optimum temperature range and will hasten the failure of other parts in the system. Running your truck without thermostats is a lose-lose situation.

You will wind up burning up excess fuel on each cold start and will clog the catalytic converter, among other things. Although it may sound like a practical solution when thermostats continually fail, replacing the engine may be best.

While you may encounter other truck owners who swear that their vehicles run fine without thermostats, it is all a question of how quickly your truck engine heats up without one. The primary purpose of thermostats is to hasten the time in reaching optimum running temperature from a cold start and maintaining the ideal temperature range.

Why Do I Need A Thermostat?

The combustion engine is a marvel of engineering. In today’s modern trucks, it is chiefly operated by sensitive electronic sensors and computer modules. These systems are fine-tuned at the factor, with the prototype vehicle running on a dynamometer to ensure that all of the operating settings are ideal. 

When you upset that delicate balance, you are certain to run into incomplete combustion problems and other running issues. When the fuel does not burn up completely, it leaves carbon deposits, contaminates the oil, and causes misfires that damage the engine. 

The particulate matter from the incomplete combustion also clogs up particulate filters and catalytic converters. It can foul plugs and coat the surfaces of sensors. Your vehicle will also lack power and may stall out altogether. 

It appears that those truck owners who run their vehicles without thermostats are not driving them very far. These vehicles may quickly come up to operating temperature without thermostats installed. 

These drivers are still wasting fuel when they bring their vehicle from a cold start and may suffer performance issues in the early minutes of operation. In addition, they probably live in regions of the country that are unseasonably warm all year round.

Truck owners who live in colder environments, however, are more likely to suffer serious drivability issues without thermostats. If the vehicle engine is already moderately warm from the warm weather, and the engine is small enough, it may quickly reach operating temperature if the truck loads are sufficient. 

Research shows that most of the wear put on an engine occurs during cold starts. This is because the oil is not pumping at peak performance to coat the mechanical parts and protect them from wear. Imagine the extensive wear of an extended cold start when drivers remove the thermostats.

Combustion engines are already under extreme stress. The pistons are nearly at their boiling point and expand to precisely fit the cylinders at operating temperatures. When the pistons expand and reach optimum running temperature, they improve the combustion and efficiency of the engine by forming a tighter seal with the cylinder walls. 

While it is certainly safer to run an engine cold than it is to overheat it, the long-term damage is comparable and will destroy the engine in both cases.

Overheated engines from failed thermostats will blow the head gaskets and possibly warp the engine or cylinder head mating surfaces. If you see white plumes of vapor rising like smoke from your engine bay, shut it off immediately.

Understanding Stoichiometry And How It Affects Your Vehicle

One of the key elements of running an engine is stoichiometry. Stoichiometry is the study of chemical reactions and quantifying the ratios of reactants to achieve them.

As applied to engine combustion, it is used to determine the most efficient fuel and air mixtures for complete combustion. This science provides engineers with different temperature ranges in calculating optimal fuel efficiency. 

For gasoline engines, the Stoich ratio is 14.7:1. This means that maximum combustion is achieved at 14.7 parts of air for every 1 part of fuel. These parts can be grams, gallons, moles, whatever formula you use to measure them or convert them into. In any regard, the formula is the same. 

However, as a general rule, more fuel is necessary to run the engine for every degree colder it may be. So if you are running vehicles without thermostats, it is going to circulate more coolant through the radiator and take longer to heat up. As a result, the truck engine is going to consume more fuel and will not run optimally. 

Do I Need A Thermostat In A Diesel Truck?

Things become even more complicated if you have a diesel engine. A diesel engine typically has two thermostats. This dual thermostat system is important to keep diesel fuel combustible in that ideal pressure-ignition range. 

The first of the thermostats in this system operates exactly how the gasoline engine operates. It retains the coolant in the engine block and does not allow flow into the radiator heat exchange. The thermostat then opens up when it reaches the ideal temperature and allows coolant flow of the radiator for maintaining it. 

The radiator has a maze of small fins and fine tubes that reduce the temperature of the coolant as it passes through the network. Cold air from fans and natural induction created by the aerodynamics of driving the vehicle at high speeds keep the engine from overheating.

The second of the thermostats in a dual diesel system usually activates under load. It opens up to allow additional cooling when the engine is being pushed harder. If someone drives their diesel truck minimally around town, they may never notice that there is a problem. 

Why Does My Thermostat Keep Breaking?

The core reasons for repeated failure are from overheating or being exposed to sludge if the parts are new and of sufficient quality. A few othe causes include:

  • Improper installation
  • Defective parts or low-quality parts
  • Improper coolant/water ratio
  • Clogs in the cooling system
  • Defective water pumps
  • Loose serpentine belts.

There is probably an underlying problem with the cooling system that is leading to premature failure. You can test the thermostats yourself, if you think it is defective after removal, by boiling it in water. It should open once it reaches a specific temperature, whatever temperature it may be rated.

Why Do I Need Thermostat Sensors?

A lot of drivers don’t realize that their trucks are running hot because their temperature sensors are bad. Temperature sensors are made of a semiconductor material that builds up internal resistance over time.

It is common for temperature sensors to give readings that show the engine at a much lower temperature than it is actually operating at when warmed up. A faulty temperature sensor can typically be replaced for under $100 and should be part of any regular tune-up. Your truck will waste a significant amount of fuel and will lack power if this item fails. 

Oxygen sensors, MAP sensors, and mass airflow sensors also play an important part in fuel management. A lot of these sensors won’t even work unless the engine or sensor itself is brought up to the correct operating temperature. For this reason, many oxygen sensors have their own heating elements and can cause serious performance and fuel economy issues if they fail.

How Does Coolant Relate To The Thermostat?

Test strips are now available to ensure that coolant is still performing it’s job. These test strips can provide notice of the pH levels, contamination, and the potency of the antifreeze properties.

Coolant prevents internal corrosion and helps the engine to operate at stable temperature ranges. If the coolant is watered down or contaminated, the system will not be able to transfer heat as well and can destroy thermostats.

Coolant does not have to be changed annually. In fact, if you take your vehicle for a repair that requires draining of the coolant, it is often collected and reused. As a general rule, the coolant should be flushed every 4 or 5 years or after every 30,000 miles. Always consult with the dealership that services your make and model to be sure. 

By properly maintaining belts, timing belts, water pump replacements, hoses, and coolant flushes, you are unlikely to encounter problems with your thermostats. Most thermostats are replaced right along with the water pump whenever the timing belt is replaced. This is because the timing belt often needs to be removed to get at the water pump and, therefore, is less labor when all are replaced concurrently. 

John Nelson

You can find John stringing a hammock from the back of his SUV to a tree camping in the outdoors most weekends during warmer weather. John loves the outdoors and the freedom four-wheel-drive vehicles offer.

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