Distinguishing a Cars Clatters Ticks and Grinds for what they are
A customer walks into his friendly neighborhood new car dealer and says there is a rattle in the back of the car and it is just driving him crazy. The noise isn’t present when the convertible top is down, if that is a clue. The job is assigned to a mechanic who takes the car for a test drive. He hears several squeaks and rattles and notes that this car, a four year old convertible, exhibitsshakeas well. The mystery isn’t so much what is making the noise as which noise is the one that aggravates the owner.
After several trips back and forth to the dealer and several noises tracked down and corrected, the owner still hears that one annoying noise. He begins to wonder if these “factory trained mechanics” know what they are doing. Another attempt is made at finding the source of the noise. One of the car wash boys is placed in the trunk of the car and the mechanic drives down cobblestone streets and over railroad tracks. Climbing out of the trunk, the boy, rubbing his back where the bumper jack kept hitting him, identifies a noise in the left rear quarter panel. He indicates it is near the fuel filler pipe. The mechanic discovers a broken spring in the gas cap permitting the cap to rattle about. The cap is replaced and the noise is cured. The owner notes that he wondered why the cap would tighten correctly when he fueled up. (A true story!)
By its nature, a machine such as a car is going to make noise. Some noises are harmless and normal; some are the harbinger of trouble. A noise analysis follows some logical steps as described below.
Assume you are the mechanic and a customer has complained about a noise you must locate and correct. You go outside and assess the car; the age, mileage and general condition can give clues about where to look.
You start it up. There is an immediate ticking noise from the engine that fades after a minute of running – a classic valve lifter noise. Not harmful unless it continues when the engine has warmed up, which means one or more lifters are faulty and should be replaced or one of the oil passages supplying the lifter is plugged. Although modern engines can live with extended oil change periods, the periodic changes still need to be made. Failure to comply with the owner’s manual can lead to small passages getting blocked and causing mayhem.
You also detected a squeal when the engine started. The squeal sounded and then faded, but it squealed again if you rev the engine hard. Since no furry beast scurried out from under the hood upon start-up you can assume a worn or loose fan belt. You check the ammeter and note that the alternator is charging; had it not been charging the alternator could have been a suspect for the cause of the squealing belt.
Stepping out of the car while it is running you note that the exhaust system is noisy and leaking. You inspect the tail pipe and note that the exhaust tone has a skip in the rhythm indicating one or more of the cylinders have chosen not to join in the party, at least at idle.
You raise the hood and listen to the engine idle roughly. You detect a sharp snapping sound at even intervals. You race the engine and the snapping sound frequency matches the engine speed. You trace the snapping noise to a spark plug wire arcing to the engine block instead of firing a spark plug. You reroute the wire and the engine idle evens out; you can replace that wire and inspect the others in the shop. Once a spark plug wire arcs the insulation has been breached; you can reroute it but it will fail elsewhere in short order.
You hear what sounds like a valve lifter ticking, but closer inspection shows a broken bolt where the exhaust manifold is bolted to the cylinder head. The gasket is leaking and the noise sounds exactly like a noisy lifter.
You close and secure the hood and proceed to take a test drive. You put the automatic transmission in gear and hear and feel a clunk. This indicates excessive free play in the drive line. It could be a worn universal joint in the drive shaft or a worn differential in the rear end. As you drive away it seems to pull smoothly, exonerating the universal joints. You hear a whine from the rear of the car, indicating a differential problem. It could be anything from the differential gearing to a rear wheel bearing, but the clunk would point towards the differential gearing. (Cha-ching! The sound of money going into the shop’s till! This can be expensive.)
Pulling out of the dealership parking lot, you hit a bump and hear a loud clunk from the area of the right front of the car. You also felt a shock in the steering wheel. Something is amiss in the front suspension so you pull over. Raising the hood you inspect the right front suspension and note the rubber bushing normally located at the top of the shock absorber is worn and hard. The worn bushing is permitting the shock to rattle about. The bushing could be replaced but this usually means the shock is worn out as well and it is time to replace the front ones at least. Back in the shop you will inspect all of the front suspension components because it appears this car has been neglected.
You also noted when you pulled over, that you heard a squealing, scrapping sound from the rear. This car has disc brakes up front, and drum brakes in the rear; and the sound you heard was the metal on metal noise indicating the brakes are worn out. You need to inspect all four brakes for this customer.
You accelerate down the road and the car pulls smoothly, shifts appropriately without noise or hesitation, and down-shifts correctly when you stop. When you step on the accelerator hard and quickly the car hesitates for an instant and you hear a popping noise from under the hood. The fuel enrichment necessary under sudden acceleration is not happening so there is something in the fuel system not up to par.
You pull into a side street and execute a“K-turn”.You notice a louder than normal whine from the power steering system. This indicates either the power steering fluid is low or the pump is failing. You also note a shudder in the steering wheel as you approach full turn in one direction or attempt to turn the wheel quickly. This indicates the pump can’t apply full pressure when demanded.
You return to the shop and pull into a repair bay to put the car up on a lift. With the engine still running you raise the hood and note a rough grinding noise that was not evident when the engine was cold. You shut the engine off and tug on the water pump pulley which wiggles slightly. The water pump bearing is worn out and the pump will soon begin to leak and fail completely.
The list is going to be expensive for this customer. As you go from front to back in your inspection you find the right front wheel and spindle has too much play in it meaning the ball joints are worn out. You note that there is no evidence they have seen any grease in a long time so that is the reason they are worn out. The front shocks must be replaced as well.
The water pump must be replaced. The power steering fluid was low so that can be corrected but running low on fluid has damaged the pump and shortened its life. The fan belt is worn, glazed and on the verge of failing; replace it with the water pump.
The ignition wiring is dry and cracking and must be replaced. The broken exhaust manifold bolt will have to be replaced. Failure to replace the broken bolt will let the leak continue and that will erode the exhaust port. At that point a new bolt and gasket will not be able to seal it. The exhaust system is leaking at the muffler and can be repaired.
The drive shaft universal joints are good but they could use some grease. There is excessive free play in the differential and it will have to be repaired. The rear wheel bearings will be inspected when the differential is removed and this would be a good time to replace them. The rear brake drums will have to be replaced because the brakes were worn out. The owner didn’t attend to them at the first sign of distress and the metal to metal contact has worn the drums beyond repair.
One final note and this is with regard to customer relations. Many people get attached to their cars like they are a member of the family. They remember taking the wife to the hospital in this car when she was about to deliver their first child. The whole family took great vacations in this car. It has started every day, even when it was well below freezing.
An honest mechanic once told a customer that his old Chevy was worn out and just not worth the money to fix it. The car was old and parts had become very hard to find too. The owner was crushed. It had been the best car he ever owned and he couldn’t bear to part with it. The elderly owner, with a tear in his eye, drove, clunked, rattled and smoked away down the street.
