Most of the fault-tracing we have to do is routine. Now and then we have to scratch our heads a bit longer to solve a problem, with the result that the incident usually ends up in a Casebook story. However, the other day we had a topsy-turvy case; a solution in search of a problem.
The fun started when an elderly Mazda 323 belonging to Sean, one of Japie’s friends, was brought in for a basic service. Japie did the necessaries and parked the car to one side with the bonnet open prior to taking it for a spin.
A few minutes later he was asked to move it and, as he pulled away with the bonnet still open, Hennie, who needed the space, said: “Japie, why does the engine rock so much? Stop, and let’s investigate.”
Together they performed the usual test for engine mountings: let the clutch out slowly while in first gear, with the engine revs slightly above idle and one foot on the brake pedal. The engine block should move only slightly in the opposite direction to engine rotation. In this case the engine movement was excessive, so they scrutinised the mountings and found the top unit on the driver’s side was in a sorry state.
On a front-wheel driven car this mounting prevents the engine from tilting as it starts to deliver torque, so the car should have been undrivable, but the young driver had never complained.
As part of a training exercise, Hennie then asked Japie to accompany him on the road to find out what effect the worn mounting had on the car’s behaviour. It was immediately noticeable that there was a severe judder on pullaway and later they heard a knocking sound over the slightest bump. A mild torquesteering effect also showed up under hard acceleration, but the overall driveability was not as badly affected as Hennie expected.
“What else did you expect to find,” asked Japie? “A worn mounting often affects the thottle linkage, causing unintended acceleration and on some engines the exhaust system eventually cracks and may even break off,” Hennie replied.
He forestalled the next question by saying, “The engine movement causes torque steer by pulling the driving wheels to one side via the drive shafts because the latter sprout out of the engine/gearbox housing.”
Why did Sean not complain? It was his first car and he was prepared to make allowances for the fact that it was old. We allowed him to pay for a new engine mounting in instalments for the pleasure of seeing his face light up when the rejuvenated Mazda was presented to him.