- Water pump
- Engine block and head
- Thermostat
- Upper hose
- Radiator and fan
- Lower hose
- Back to pump
- Compressor
- Condenser
- Drier or accumulator
- Expansion valve or orifice tube
- Evaporator
- Back to compressor
Engine cooling
Coolant circulates through the engine, picks up heat, and gives it off at the radiator. A thermostat controls when coolant flows to the radiator, and a fan pulls air through when the vehicle is moving slowly.
Common parts
- CH·1Radiators and radiator caps
- CH·2Water pumps and pump gaskets
- CH·3Thermostats and housings
- CH·4Electric cooling fans, fan clutches, shrouds, and fan relays
- CH·5Coolant reservoirs and caps
- CH·6Coolant temperature sensors
- CH·7Oil coolers and transmission coolers
Signs of trouble
A temperature gauge that climbs, steam, a sweet smell, or a puddle of coolant are the obvious signs. A thermostat stuck open can leave the engine running cold, with weak heat and poor fuel economy. A stuck-closed thermostat can overheat the engine quickly. A whining or wobbling water pump pulley, or a drip from the pump’s weep hole, points at the pump.
Finding the right fit
Radiators vary by engine, transmission type, and towing package, and some have built-in transmission or oil coolers. Thermostats come in different opening temperatures; use the one the engine maker specifies. Fans and shrouds often differ between engines in the same model.
Heating and air conditioning
The heater uses hot coolant passing through a small core behind the dash. The air conditioning system compresses refrigerant, cools it in the condenser at the front of the car, and lets it expand in the evaporator inside the dash. Doors and actuators in the dash blend and route the air.
Common parts
- 1A/C compressors and clutches
- 2Condensers, evaporators, and receiver driers or accumulators
- 3Expansion valves and orifice tubes
- 4A/C hoses, lines, and service valves
- 5Heater cores and heater hoses
- 6Blower motors and blower resistors or control modules
- 7Blend door and mode door actuators
- 8Climate control panels and switches
Finding the right fit
A/C parts depend on the refrigerant type, which is printed on a label under the hood. Many newer vehicles use a different refrigerant from older ones, and the two are not interchangeable. Compressors differ by engine and by clutch style. When a compressor fails internally, many makers require a new drier or accumulator and a flush for the warranty to apply.
Before you order
Start with the year, make, model, and engine, then narrow it down with the trim, drive type, and any option the part depends on. The VIN is the most reliable way to do that, because many parts catalogs and dealer counters decode it to the exact build. If the old part is in hand, its original-equipment number is the best cross-reference. Aftermarket brands publish their own numbers and usually list the original number they replace. Two listings that both say they fit can still differ, so compare the photos, connectors, mounting points, and the notes in the listing. The find the right part guide covers this step, and the all makes reference lists each maker’s official parts catalog.
Once you know the part number, compare the same number across stores. Look past the first price at the core charge, shipping, the return window, and what the warranty covers and who honors it. A remanufactured part, a new aftermarket part, and an original-equipment part can each be the right choice, but they are not the same purchase. The compare prices and warranties guide walks through what to read. Prices on PartIndex carry the date they were recorded, so confirm the current price and fitment with the retailer before you buy.
Do not open a hot cooling system. A/C refrigerant is under pressure and can cause frostbite, and in the United States it must be recovered with proper equipment rather than vented. Some newer refrigerants are mildly flammable.