When air is drawn into the turbocharger, boosted, and then forced into the engine, it gets very hot. And hot air isn’t as good for an engine as cool air. Therefore many turbocharged engines make use of an intercooler.
An intercooler is basically an air-to-air radiator. The hot air from the turbo enters at one end, and as cooled as it passes through the intercooler (much like the water in a car’s radiator) before entering the engine at a much lower temperature.
This allows the engine to make full use of a simple principal of physics; cooler air is more dense than hotter air.
This basically means that for a given volume (of our engine’s cylinder for example) we can get more oxygen into the same space when the air is denser – and more oxygen means better performance.
01 Leaking boost hoses
There’s not much that can go wrong with an intercooler, so most faults are usually either associated with installation issues or physical damage resulting in boost leaks.
One of the most common areas affected is the rubber boost hoses and the clamps that hold them inn place. Over time the rubber will perish, and clamps can lose their clamping force, which can result in the boost hoses actually allowing boosted air to escape.
This would result in a sluggish, underperforming car, and you may even be able to hear a ‘whooshing’ sound (although not always) as you can actually hear the air leak when driving.
The fix is quite simple; new hoses and clamps.
02 Impact damage
As the intercooler sits right at the front of the car it does mean it is susceptible to damage, particularly from stones and debris from the road hitting the intercooler.
This can damage the delicate cooling fins, reducing the cooling efficiency of the intercooler, and is extreme cases and also damage the tubes through which the boosted air passes through.
The most common effect is an underperforming intercooler, resulting in increased inlet air temperatures, but in the worst cases the intercooler can piece and you can end up with a boost leak.
The fix requires a new intercooler.
03 Oil contamination
As the air that enters the intercooler comes directly from the turbocharger, it does mean that if you’ve ever had any issues with the turbo then the intercooler is likely to be affected too.
For example, if a turbo is suffering from an oil leak die to worn seals, then the oil that has ‘leaked’ out has to go somewhere – and the somewhere is most likely to be the intercooler.
This means the oil gathers in the bottom of the intercooler, reducing the performance of the intercooler itself. It also introduces oil vapours to the boosted air, so will have a negative affect on engine performance too.
To check, remove the boost hoses and inspect for signs of oil contamination. If there are any, remove the intercooler and flush our with engine degreaser to remove all the oil from the inside of the intercooler.