Clive Atthowe: Audi S7 fault

Technicians who share their experiences of faults and fixes within the workshop are a valuable resource to peers – helping to reduce downtime and head scratching, confirming correct process and instilling confidence in those less experienced. Here, Clive Atthowe of CAT in Norwich, details the problems affecting an Audi S7 that was brought into this workshop and highlights the importance of initially checking for Technical Bulletins.

On page 61 & 62, we revisit Steve Scott, founder of the SimplyDiag Network, with Edward Grigg at his Swanley garage, who detail a couple of faults & fixes as part of Steve’s mobile training offer. On page 64, Andy Crook outlines Oscilloscope Basics: Setting voltage, timebase & triggers. From page 68, Peter Melville, founder of the Hybrid and Electric Vehicle Repair Alliance, provides an overview of regenerative braking and the implications on servicing.

CASE STUDY: Audi S7 – engine stalling

Turbos removed, old turbos

By Clive Atthowe

We had a customer bring in their Audi S7 V8 twin turbo recently, complaining that the engine was stalling and was then difficult to start. He also mentioned that on starting, an unusual noise was heard. The vehicle had been recovered to the workshop and after checking visually for any signs of issues, alongside basic levels, we started the car with no apparent issues.

"After allowing the engine to warm up at idle we then increased engine RPM, it was then that we heard an alarming noise..."

New oil strainer was placed into housing prior to reassembly

which increased with engine speed but was also present on lifting off the throttle. The noise appeared to be coming from the turbo area of the engine and a severe vibration could be felt on the n\s turbo. After consulting with the owner, we stripped off the inlet pipe work to inspect the turbos. The n\s turbo bearings had failed completely, and the compressor wheel was machining itself into the housing. There was also wear in the o\s turbo. We decided to see if there were any technical bulletins relating to the failure and there was a known issue. The symptoms matched the customer’s description of stalling followed by poor starting. The turbos can be starved of oil when a small oil strainer where the turbos oil feed originates from becomes restricted and reduces the oil flow. This results in turbo bearing failure.

Having established the failure and cause we again consulted with the owner and he approved the repair, which was quite substantial. It requires putting the front of the car into service position, removing the turbos complete with manifolds and stripping out the centre cover to access the oil strainer and non-return valve. The oil strainer was replaced along with a new non-return valve and we could start to rebuild.

Two new turbos were installed along with all new oil feed and coolant pipes. All gaskets were also replaced, as well as new studs and fittings as required. A new, genuine air filter was installed and we introduced fresh engine oil and new filter. The cooling system was vacuum filled with new, genuine antifreeze and with the oil system primed, we ran the engine up to temperature. After inspecting for leaks, the final check was an extended road test to confirm correct operation and boost.

The vehicle was restored to normal operation with normal starting idle and turbo boost.

Making an enquiry?

Please mention you saw it in Autotechnician!

Authorised Distributor of Castrol

Specialist in supporting Independent Workshops

ASK US TEL: 0800 371910 ABOUT THE CASTROL ENGINE STAND OUT FROM THE CROWD BECOME PART OF A NETWORK WARRANTY THAT OFFERS REAL BENEFITS TO YOU AND YOUR CUSTOMERS

• Operate under Castrol’s trusted brand to help your workshop stand out from the competition. • Enhance your business identity across all consumer touch points with the Castrol Service brand. • Gain more knowledge about lubricants from our team and through online training solutions. • Become part of our online network, driving more customers to your workshop through Castrol.com • Offer Castrol Engine Warranty to your customers

ONE CASTROL OIL-CHANGE ONE YEAR’S NEW ASK US ABOUT ENGINE WARRANTYTHE CASTROL ENGINE ZERO WORRIESWARRANTY

FOR YOUR CUSTOMERS

For full terms and conditions visit www.castrol.co.uk/warranty

ONE CASTROL OIL-CHANGE ONE YEAR’S ENGINE WARRANTY ZERO WORRIES

Only applicable to Castrol products. From date of registration, covering engine damage only.For full terms and conditions visit Customer must register. This does not affect your statutory rights.www.castrol.co.uk/warranty

Only applicable to Castrol products. From date of registration, covering engine damage only. Customer must register. This does not affect your statutory rights.

Castrol Engine Warranty Poster A3.indd 1 26/08/2020 12:04