Symptom guides
Start from the symptom. End with a measurement.
Each guide lists the causes a symptom could have, then the tests that tell them apart, with the tool and the value to expect. No cause is ranked before a reading exists.
Common-rail diesels, roughly 2004 onward
Diesel cranks but will not start
A common-rail diesel that turns over and never fires. The possible causes, then the tests that split them, with the tool and the value to expect.
6 causes · 4 tests →
Turbo diesels, any age
Judders under load with black smoke
A diesel that shudders on a hill and puffs black smoke with no warning light. Possible causes, then the tests that split them.
6 causes · 4 tests →
Any disc-braked car or van
Brake squeal, only when cold
A squeal from one corner on the first few stops that disappears when the brakes warm. What causes it and how to prove which one it is.
5 causes · 4 tests →
Any water-cooled engine
Overheating with no visible leak
Coolant temperature climbing with nothing on the floor. The causes, then the tests that separate a cooling fault from a head gasket.
6 causes · 4 tests →
Petrol engines with port or direct injection
Rough idle when cold, smooth when warm
A petrol engine that shakes for the first two minutes and then runs clean. The causes and the tests that separate fuelling from a mechanical fault.
5 causes · 4 tests →
None of these is your car.
A Case takes the vehicle and the symptom in front of you, asks the two or three questions that narrow it, and names one test at a time with the value to expect.
Open your first CaseFree and complete. No account, no card.