Engine cooling: a job that must not stop
The engine in your car produces enormous amounts of heat. We are talking combustion temperatures of over 2,000 degrees Celsius inside the cylinders. Without an effective cooling system, the engine would literally melt within a few minutes.
The radiator is the central part of that system. It is that large metal piece with fins sitting in front of the engine, behind the front bumper. Coolant flows through it, carrying heat away from the engine and giving it up to the surrounding air.
The intercooler is a similar part, but it cools the air coming from the turbocharger. The turbo compresses the air, and compression heats it. Hot air is less dense, which means less oxygen in the cylinder, which means less power. The intercooler cools that air and restores its density, which increases engine power.
When either of these parts stops working properly, the consequences can be serious. Replacement with a new part is not always cheap. That is why used radiators and intercoolers have a big market, and today we will go through everything you need to know about them.
Types of radiators in a car
A modern car has several different radiators, each with its own function:
Engine radiator
The main radiator that cools the engine coolant. Usually the largest radiator in the car and located behind the front bumper. Made from aluminium (newer cars) or a combination of copper and brass (older cars).
Cooling capacity depends on the size of the radiator, the number of fin rows and the airflow. For the same engine, radiators can be different sizes depending on the market (for example, the radiator for tropical countries is larger).
Intercooler (charge air cooler)
The intercooler cools the air coming from the turbocharger (or supercharger) before it enters the engine. There are two types:
- Air-to-air intercooler - the most common type, cools the charge air using ambient air. Usually located in front of the engine radiator or to the side.
- Air-to-water intercooler - uses coolant to cool the charge air. It is more efficient but more complex. Used in some premium vehicles and sports cars.
Oil cooler
Some engines have a separate cooler for engine oil. This is especially important on turbo engines and engines working under heavy loads. It can be water-cooled (mounted to the engine block) or air-cooled (a small radiator).
Automatic transmission cooler
Automatic transmissions generate a lot of heat and need cooling. The ATF cooler is usually integrated into the main engine radiator or is a separate small radiator.
AC condenser
Technically not a radiator in the classic sense, but it looks the same and is mounted in front of the engine radiator. It cools and condenses the refrigerant in the AC system.
Symptoms of a faulty radiator
How do you spot a radiator that needs replacing?
- Engine overheating - coolant temperature rises above normal, especially in traffic or at low speed
- Visible leak - green, pink or orange fluid under the car (depending on the type of antifreeze)
- Crusty radiator - white or green traces on the fins that point to small leaks
- Clogged fins - radiator fins full of leaves, insects and dirt that reduce airflow
- Internal blockage - corrosion and deposits inside the radiator reduce coolant flow
Symptoms of a faulty intercooler
- Loss of power - the engine does not pull like before because the air entering the engine is not cool enough
- Higher fuel consumption - the ECU compensates for the higher intake air temperature with a richer mixture
- Smoke from the exhaust - black smoke on diesels can point to intercooler problems
- Oil leak - on turbo engines, oil from the turbo can leak through a damaged intercooler
- Air noise - hissing or whistling that points to a crack or loose connection
Checking a used radiator
The radiator is one of the parts that is relatively easy to check before buying. Here is what to do:
Visual check
- Fins - check whether the fins are straight and undamaged. Bent fins reduce airflow, but can be straightened with a special fin comb.
- Plastic parts - on radiators with plastic top/bottom tanks, check for cracks or leak traces at the joints between the plastic and the aluminium
- Connections - hose stubs must be undamaged and free of corrosion
- Inside - look through the opening. The inside should be relatively clean, without excessive corrosion or deposits
Pressure test
The best way to check a radiator is a pressure test. Plug all the openings except one, connect a pressure pump and submerge the radiator in water. Apply 1 to 1.5 bar of pressure and watch for bubbles. If bubbles appear, the radiator is leaking.
This is a simple test you can do yourself, or ask a mechanic to do. It takes a few minutes of time, and can save you from buying a faulty radiator.
Flow check
Clogged channels inside the radiator reduce coolant flow. You can check flow by running water through the radiator. It should come out evenly from all the channels. If some channels do not let water through, the radiator is partially clogged.
Checking a used intercooler
The intercooler is checked in a similar way to a radiator, with some specifics:
- Pressure test - plug the outlet, apply 1.5 to 2 bar and watch whether it holds pressure. On air-to-air intercoolers, leaks are a common problem.
- Internal condition - look inside the intercooler. A thin film of oil is normal (it comes from the turbo), but large amounts of oil or deposits point to turbo or PCV valve problems.
- Fins - as with radiators, the fins must be straight and undamaged
- Connections - rubber or silicone joints must be elastic and undamaged
Used radiator and intercooler prices
Engine radiators
- VW Golf/Passat: EUR 40 to 100
- BMW 3/5 series: EUR 50 to 150
- Audi A4/A6: EUR 50 to 130
- Renault Megane/Clio: EUR 30 to 80
- Mercedes C/E class: EUR 60 to 160
Intercoolers
- VW 1.9/2.0 TDI: EUR 30 to 80
- BMW N47/N57: EUR 50 to 120
- Renault 1.5 dCi: EUR 25 to 70
- Ford 1.6/2.0 TDCi: EUR 30 to 80
For comparison, a new radiator for an average car costs EUR 100 to 300, and a new intercooler EUR 80 to 250. The saving with used is 50 to 70 percent.
Fitting a radiator costs EUR 80 to 200, and an intercooler EUR 60 to 150.
When buying a used radiator pays off
Radiators are generally a safe second-hand buy, but there are situations when used is the better choice and when it is not:
When it IS a good idea:
- The car is older and the price difference is significant
- The radiator has passed a pressure test and is visually in good shape
- It is a simple aluminium radiator without an integrated ATF cooler
When it is NOT a good idea:
- The radiator has an integrated automatic transmission cooler (if the internal cooler leaks, ATF mixes with coolant, which is a disaster for the gearbox)
- The price difference between new and used is small (EUR 30 to 50)
- The radiator has plastic tanks that are brittle and prone to cracking
Fitting tips
When fitting a used radiator or intercooler, here is what to watch out for:
- Flush the cooling system - before fitting a new radiator, flush the whole system of old coolant and any deposits
- New coolant - put in fresh coolant of the correct specification
- New thermostat - if the thermostat is old, take the opportunity and replace it (costs EUR 15 to 30)
- New hoses - if the rubber hoses are hard or cracked, replace them
- New caps - the radiator cap (expansion tank cap) has a valve that regulates pressure. If it is old, replace it.
Radiator and intercooler: a safe used purchase
Used radiators and intercoolers are among the safest used parts to buy. They are easy to check, relatively cheap, and the saving compared with new can be significant. The keys are the pressure test and a visual check of the fins and connections.
Need a radiator or intercooler for your car? Send a request via PoDi and you will get offers from several suppliers with prices and details on the condition of the parts.