We were contacted by a local garage who were desperate for us to try and help resolve a problem on a Mini Cooper S that they had been trying to repair . The initial consultation revealed that the fault suddenly occurred whilst the owner was driving under load and experienced a lose of power . The garage had been trying to resolve the problem over a week but mostly by replacing likely parts that they thought might cause the issue . The vehicle had been previously mapped and the owner had taken the vehicle back to the mapping company only to be told that the fault was caused by turbo failure with no apparent evidence of the diagnoses. Initial testing revealed a fault for low boost testing on our rolling road revealed very low boost and severe lack of power. We started our diagnoses of the low boost with a pressurised inlet smoke test which proved that the inlet system was intact . We inspected the turbo and whilst there was some evidence of wear the turbo was free and we could see no reason why it shouldn’t produce boost . The control side of the turbo wastegate was checked using the engine management actuator output tests , this also proved that the turbo wastegate control was working normally . So the only control other element on the turbo boost control is the turbo recirculating valve . On this application the valve in an integral item built into the turbo housing . When the valve was removed it was obvious that the diaphragm had failed this has the effect of causing a constant re-circulation of boost and prevents boost from building . Replacing the valve restored boost to the correct requested levels and we retested the vehicle in our rolling road to prove the results . The conclusion is that lack of knowledge of the turbo system by both the mapping company and the previous garage had caused an incorrect diagnoses and a lot of unnecessary parts to be fitted .
Mini Cooper S Rolling road testing..
Failed recirculating valve diaphragm..
Rolling Road graphs Red before Yellow after..
