General Auto Info

Cooling System

Coolant | Radiator | Thermostat | Water Pump

The cooling system’s purpose in modern automobiles is to maintain proper engine temperature by circulating liquid throughout the engine and a radiator. This same fluid serves to heat the interior air of the cabin if the heat is on. Coolant or Antifreeze is the fluid used in this application. It is a chemically engineered fluid that has a very low freezing point and a high boiling point. Your engine doesn’t want ice and it doesn’t want steam. The chemical composition of the coolant is what keeps your car’s engine from bursting like a frozen soda can in the freezer and from popping like a champagne bottle in your hot trunk in the summer. The flow of coolant is powered by a water pump and regulated by a thermostat. The thermostat remains closed and blocks the flow of coolant in your engine until the engine is at its operating temperature. Once the engine is warmed up, the thermostat opens and coolant flows throughout the engine.

Fuel System

Fuel Tank | Pump | Filter | Lines | Pressure Regulator | Rail | Injectors

Fuel is the, well fuel, of your engine. Whether it’s 85 octane sold in high altitude markets or 93 premium found in most cities you need this stuff to flow reliably into the combustion chamber. Fuel is sprayed into your intake manifold/plenum (or directly into the combustion chamber in newer “direct inject” engines) where it mixes with air and is then ignited by a spark plug. To make this all happen there are many components involved. Let’s run through them one by one. I’ll be talking about gasoline, but many of these ideas and components translate to diesel engines as well.

Fuel Tank

The fuel tank is commonly located in the back of the car underneath the trunk and rear seats. It’s filled with gasoline or diesel (which I hope is obvious at this point) and is really just a large sealed container with a few spouts and hoses connecting it to other components of the vehicle. The filler neck connects the tank to your fuel filler cap which, in today’s vehicles, is sealed. The fuel vapors expand and contract with temperature changes and it’s important that those vapors have somewhere to go. Temperature driven pressure can have tremendous power and could allow a perfectly sealed tank to burst. Old cars used to have a vent in the cap which would simply allow gasoline to escape into the atmosphere when the tank was pressurized. Of course, that’s not great for our environment or your gas mileage so today we have excellent ways of eliminating this useless waste of fuel and using it to power the engine. Evaporative Emissions equipment has been required on new cars for decades and provides gasoline vapors a place to hang out until the engine can use them. Activated Carbon canisters or “Charcoal Canisters” are connected to the fuel tank and can store gasoline vapors. When the engine is warm these vapors are drawn into the engine and burned off. Clever.

Fuel Pump

The fuel pump pushes gasoline from the bottom of your tank up towards your engine. The pump typically has a mesh cover or filter over the pickup of the pump so any solids in the tank don’t cause trouble in the fuel system. If a car sits for a long time (sometimes as little as 6 months) a fuel pump can be one of the first casualties. I’ve bought a few used cars that have sat un-started for over a year and every single one needed a new fuel pump.

Fuel Filter

A Fuel Filter is normally found near the fuel tank and filters the gasoline soon after it leaves the fuel pump. Many manufacturers since the 1990’s use a “lifetime” fuel filter which is not intended to need regular maintenance. If this is the case I wouldn’t suspect the filter to cause problems unless you suspect previous neglect of the fuel system. I’ve dealt with some really dirty fuel tanks and pumps and never had a problem with a filter. Your results may vary.

Fuel Lines

Fuel Lines carry the fuel from the tank to the engine. Usually this means running under the car along the frame rail of the chassis. Fuel lines need to be protected and safe from road debris. A punctured fuel line can easily mean a serious fire and manufactures go to great lengths to ensure that doesn’t happen.

Fuel Pressure Regulator

The fuel pressure regulator is located on the fuel rail in the engine bay. This component regulates the pressure going into the engine’s fuel rail where it will soon be delivered to the injectors. The pressure regulator keeps pressure the same regardless of how much fuel is flowing. This ensures predictable flow whether you’re stopped at an idle or flooring it to get on the freeway (faster than the stranger next to you, of course). Without a regulator the engine would have a very difficult time knowing how to control the injectors to keep your engine running. The excess fuel is diverted from the regulator back into the fuel tank where the fuel gets another chance to make it all the way to combustion.

Fuel Rail

Finally we’re getting close to the point of explosion. The fuel rail distributes fuel to each injector. Normally, vehicles will have one injector per cylinder and another injector to help the engine start when cold by adding even more fuel. Fuel rails are typically very simple extrusions of aluminum with holes and fittings to connect all your injectors and the regulator. No magic here.

Fuel Injectors

These are normally placed directly between the fuel rail and the intake manifold or cylinder head. Injectors are responsible for creating a fine mist of gasoline which will mix well with air. Injectors are normally assigned one per cylinder and another upstream to serve as the “cold start injector”. These injectors are constantly switching on and off. They are controlled by the Engine Control Unit or ECU to flow the perfect amount of gasoline to mix with whatever air the engine sees at any given moment. The duty cycle (see explanation here) is varied to supply the right amount of fuel. Injectors must be sized correctly to allow enough fuel to flow into the engine. When upgrading engines well beyond their factory spec new injectors are commonly needed. Running lean (too little fuel) or rich (too much fuel) hurts either your engine, fuel economy or both and is avoided by the ECU’s programmed “maps”. These maps tell the engine, “When you see this much air, supply this much fuel” and take into account air temperature, engine temperature, RPM, throttle position and a variety of other things pending the specific engine configuration.

Once the fuel is sprayed into the intake path close to the combustion chamber it mixes with air and flows through the intake valve.


Sounds simple enough but using the wrong size is an easy mistake and leads to stripped screws and swearing. One size does NOT fit all.

Screwdriver P1/P2/P3 Screwdriver Flat Blade Screwdriver Finger Bit
Helpful for areas with limited access


Open End - Box End - Flare Nut Ratcheting Flex Head

Open - Most common wrench style

Box - Use this when possible to lessen likelihood of stripping bolts

Flare - Used on compression lines where avoiding stripping is critical

Ratcheting wrenches are amazingly convenient Allows access to difficult spots unlike any other simple tool

Socket Wrench

1/4" Drive 3/8" Drive 1/2" Drive Flex Head Breaker Bar
Small socket wrench for small bolts Most common socket wrench. If you have only one, this should be its size. A little more than most small jobs need, but very helpful on larger bolts Helpful in areas that aren't accessible with regular socket wrenches Needed for stuck bolts; provides a lot of leverage and doesn't break easily


Standard 6 point Standard 12 point Deep Socket 6 point Deep Socket 12 point Inverse Hex
Used on some head bolts


Feeler Gauges Timing Light Plastigauge Strap Wrench Vice Grips
Measure small gaps in valve shims and throttle assemblies Set ignition timing Check bearing clearances Hold hard to grab items like oil filters and shock bodies Hold nearly anything. Really hard.