Dr. Gizmo Column

 "Dr. Gizmo"
By Phil Arendt

Pop Sound During Braking

Question 1
When applying the brakes in my 2007 Ford Escape I hear a pop sound that seems to be coming from the rear.  I placed the rear on jack stands to inspect the suspension but I don’t see anything loose. 

The noise is not constant with every stop.  It occurs maybe once or twice during my daily 18 mile drive to work.  What could cause the noise?  M.D., email

Answer 1

It would be beneficial to check the rubber bushings in the rear suspension for excessive wear.  Replace if needed.  Also, check the security of the rear cradle. Sometimes a body mount may loosen due to corrosion or the rubber might crack.   

Check the rear brakes.  It’s possible a part has broken or has shifted due to excessive wear.

Additionally, sometimes a fault in the antilock brake system causes brakes to pop.  Check the system for faults, trouble codes, failed sensors or broken tone rings at the wheels.

H.V.A.C. Display Blinks

Question 2
The heater and air conditioner screen in my 2002 Isuzu Axiom began to blink and the air conditioner quit working.  I went to a repair shop where they were able to determine that there is plenty of Freon in the system.  They also did some tests but there were no codes showing a problem.  They had to jumper some wiring to get the a/c to work.  They are not sure what is causing the trouble.  They suggested that I should take the vehicle to a dealership.

Is it necessary to take my SUV to a dealer?  Can a local shop do this kind of work?  Do you know what is wrong?  Will it cost a lot to fix?  D.F.M., email

Answer 2

You exceeded the number of questions for this column.  Of course I’m just kidding.
It’s not necessary to take your truck to a dealer shop.  Consider a well-established independent repair shop for diagnosis of the trouble.  Problems such as you describe could be caused by issues such as a failed control panel, poor ground connections in a circuit, or even a failed relay.  An experienced technician should not have much trouble determining the cause.

Engine Stumbles Under Load

Question 3
The 8.1-liter engine in my 2004 Chevrolet Silverado 3500 misfires.  I have replaced the spark plugs, ignition coils, spark plug wires, fuel injectors, mass air flow sensor, catalytic converters and fuel pump all in vain.

I had the truck checked over at a repair shop.  They found the misfire is in cylinder three.  They tested the compression of all the cylinders.  It’s fine.  They also replaced the valve springs on cylinder three but this did not cure the trouble. 

They saw carbon in the cylinders so they cleaned out all of the cylinders with two different chemical treatments but no luck.  The engine continues to misfire at cylinder three.  Now they are at a loss and I’m frustrated over the problem.

The truck runs great under light loads but if I stomp on the gas the misfire kicks in when the tachometer hits 3,500 RPM.  What’s up doc?  B.T., email

Answer 3

Don’t stomp on the gas.  Problem solved.  All kidding aside the trouble is you have replaced just about everything except the kitchen sink without repairing the cause of the condition.

Check the crankshaft dampener.  It’s possible the rubber has cracked.  It’s also possible it is loose on the crankshaft or the key that holds the dampener in place is excessively worn. 

Also, ask your technician to check the crankshaft sensor.  It might have a fault.  If so, replace it.

Brake Pedal Sinks To Floor

Question 4
I have a 2005 Buick Riviera.  One day the brakes went to the floor.  When I pumped them they would be back until I used them again.

The brake fluid is full and not leaking out anywhere.  The pads are brand new.  There isn't anything wrong with the actual brakes.  

I have heard and was told the brakes need to be bled.  Is it possible for air to get in the brake line just out of the blue?  What do I do next?  T.W., email

Answer 4

Until the brake system is operating as designed don’t drive the vehicle.
When the brake pads were installed it is possible air entered the master cylinder or antilock brake system module.  At this point bleeding the system at each wheel and cycling the antilock brake module with a scan tool likely will cure the trouble. 

Also, I can’t imagine a shop released the vehicle to you in this condition.  Consider taking your car to another shop because the shop that did the brake work does not appear to have your safety and the safety of others on the road in mind.

 

Rear Turn Signal Eludes Repair

Question 5
The right rear turn signal in my 2008 Saab 9-3 quit working.  When I went to replace the bulb I found the wiring melted and a circuit board in the taillight assembly was burned.  I replaced the entire unit but it still would not flash.  I checked all the fuses and they are ok. 

All the other lights in the car work fine.  Just the right rear does not work.  What am I missing?  R.M., email

Answer 5

It’s time to trace the wiring. Start at the right rear light and work toward the power source.  Somewhere between the light and power source is an open circuit.  There might be more burnt wiring in the circuit or it is even possible the module that controls the light has a fault.  Repair all depends upon your findings.

Good luck in your endeavor.

Multiple Causes For Timing Chain Noise 

Question 6
The engine in my 2007 Mini Cooper S with 48,000 miles is making a rattling noise.  Also, the check engine light is on.

A mechanic at my local shop who specializes in Mini repairs thinks the timing chain is causing the sound.  He said that it is unusual for a car with such low mileage to need a new chain.  He won’t know for sure until he disassembles the engine.  Does this seem right to you?  T.T.S., email

Answer 6

Certainly it is possible for a timing chain to make noise at this mileage.  However, more than likely the noise is not caused by excessive wear although anything is possible.  More than likely the trouble is caused by a faulty solenoid, poor oil pressure or failed tensioner.  Repair all depends upon your technician’s findings.

Until this is repaired do not drive the car.  If the timing chain jumps, the engine could suffer severe damage.

Thank you for all the great questions.  Dr. Gizmo can’t wait to answer more.

Phil Arendt is a columnist, consultant and A.S.E.-Certified Master Technician.  Readers may send questions to Dr. Gizmo at P.O. Box 548, Cary, IL. 60013 or e-mail address mailto:drgizmo@hotmail.com.  09/16/2013 ® DR. GIZMO © 1989 - Present