Typical Citroën C4 FAULTS
INJECTOR SEAL – Failure of one or more injector seals is common according to Mark at AES, which can lead to a string of catastrophes. From the top of the engine, look for a build-up of carbon around the injector, which sits inside a tube in the cylinderhead. If there’s a sufficient amount of carbon created from the failed seal, it can harden and drop into the engine, potentially blocking the oil strainer and feed for the turbocharger (and it can block the vacuum pump). Note that when identifying an injector, number one is on the nearside (closest to the gearbox) – the one that has failed in our photograph.
AIR FILTER LOCATION – With the air filter at the back of the engine bay and concealed, it’s not only neglected during a service, but if it is changed, the rubber doughnuts that its housing is located in usually break, so they should be replaced. If they are not, then the air filter can move around, rubbing against a hard plastic coolant pipe, which eventually creates a leak and coolant loss. If the coolant loss isn’t caught in time, the engine can overheat and cause further problems, such as head gasket or even engine failure.
BLOCKED FUEL FILTER – The awkwardness of accessing the fuel filter means it’s rarely changed, not to mention having to use the hand pump at the back of the engine bay to prime it, or if that isn’t fitted, to release the fuel line shown in the photograph below (the one with the green tag), which Mark at AES says he has to connect a vacuum bleed system to bleed air out. A blocked fuel filter may result in a fuel pressure fault under hard acceleration.
ELOY ADDITIVE – A bag of Eloy should last for around 100,000 miles, but it’s only applied whenever the fuel filler cap is released – there’s a magnet inside the filler cap and upon unscrewing and removing the cap, you should be able to hear the Eloy being squirted into the tank. If you only add five or ten quid of fuel at a time, then the Eloy may run out before the 100k mark. There are no sensors to warn of this, so without the additive, which helps to lower the burn point to remove the soot inside the DPF, the DPF can block up.
RATTLY HEATSHIELD – Check the heatshield at the front of the engine bay is securely fitted. It covers and protects the DPF and turbocharger. If it’s loose, it can rattle and vibrate against the oil cooler, resulting in a leak and a much bigger problem.
– If the engine cuts out under load and/or is difficult to start, check the live data for fuel pressure and also inspect the 5V live wiring to the EGR valve and the fuel pressure sensor. They share the same live feed, which can short-circuit if water gets into the electrical plug for the EGR valve – check the plug for damp and corrosion.