Dr. Gizmo Column

 "Dr. Gizmo"

By Phil Arendt

Cold Start Rattling Sound Raises Concern   

Question 1

Recently, I purchased a 2009 Toyota Matrix with an automatic transmission and 1.8-liter 4-cylinder engine.  It has 78,000 miles and is in great condition.  The trouble is a rattling sound in the engine.  When I first start in the morning there is a brief rattling noise.  I don’t hear the rattling during subsequent starts later in the day unless the car has been parked for an extended period. 

My dad listened to the sound.  He thinks it’s coming from the front of the engine.  I’m concerned something major is about to happen.  What do you think?  C.J., email

Answer 1

Congratulations on your recent purchase.  I’m sorry to hear there is a noise concern.  Your dad might be correct.  The rattling sound might be from the timing chain.  It could be related to an issue with a tensioning device or camshaft gears. 

A few years ago Toyota issued a technical service bulletin regarding a rattling sound upon starts.  The bulletin might pertain to your vehicle.  Ask your favorite repair shop to diagnose the cause of the sound.  For them to hear the noise consider leaving the vehicle overnight so a technician can hear the rattling during the initial start when the engine is stone cold in the morning.  If the noise is the subject of the technical service bulletin a camshaft gear or gears need replacement.

Many Causes For No Heat

Question 2

There is no heat in my 2005 Pontiac Grand Prix with a 3.8-liter engine.  I replaced the thermostat but this did not solve the problem.  What else should I look for? J.B.J., email

Answer 2

You need heat.  Unfortunately, there is much more to check.  It’s possible the water pump is not functioning as designed.  Perhaps the heater core is clogged with scale.  Perhaps the system needs a flush to restore coolant flow through the system.  Maybe the heater core needs replacement due to scale buildup.  Perhaps the actuator doors in the ducts in the dash are not functioning as designed.  It’s possible the dash control head has failed and needs replacement.   Maybe air is trapped in the system and the coolant level is low.  Perhaps the recently, installed thermostat is defective.  Maybe the cooling system fans are not functioning as designed.

If you are an experienced do-it-yourselfer and have the proper tools you might be able to cure this issue.  If not, it’s time to send the car to your favorite shop.

New Fuel Pump Fails Twice

Question 3

The check engine light in my 2005 Volvo XC70 turned on and the engine stalled.  The vehicle was towed to a shop where it started but the check engine light was on.  A technician did tests and found a code for fuel pressure problems.  He replaced the fuel pump. 

The next day the same thing happened.  I was stranded.  My shop had the car towed back.  The new pump they installed had failed.  They ordered another but my Volvo stalled again after this work.

My shop says this pump is defective too.  What are the odds of this happening twice or is there something else wrong?  N.T.B., email

Answer 3

It’s unlikely but possible.  Their diagnosis probably is correct.  The pump is failing to deliver the volume of fuel the engine needs.  However, if your shop is installing aftermarket parts they might consider procuring an original equipment fuel pump from a dealership.  This might be a lasting cure as sometimes aftermarket parts don’t perform as expected.

Engine Stalls Due To Low Voltage

Question 4

Sometimes my 2000 Dodge Ram 3500 with a 10-cylinder engine idles rough, backfires in the exhaust, surges and sometimes stalls.  When this happens the check engine light is not on but I notice that the battery gauge reads all the way to the low side.  If the engine stalls it starts with no problem and runs normally.  This might happen three or four times in a week of many trips or it might not happen at all for a month. 

I went to an auto supply store to have the computer codes read.  No codes were found.  I also went to a repair shop but the truck ran fine for them during 100 miles of test drives.  They scanned the computer and found no problems.  They also checked some wiring but everything seems alright.  They said I should bring it to them when the vehicle is acting up. 

The truck has 123,000 miles.  Other than normal wear items I have not replaced any parts.  The truck is in good shape for a work truck.  Do you have any suggestions?  D.D., email

Answer 4

It’s time to find a new Ram.  All kidding aside your vehicle has many more miles of service.

Curiosity raised by the voltage gauge brings suspicion upon the charging circuit.  It shows an under voltage condition.  This might be caused by an issue in the engine control module, the charging circuit including the alternator, a failing battery and the wiring in between the alternator and engine control module. 

Your shop checked wiring but found no issues.  If the wiring they checked was in the charging circuit it must be in good shape.  If this is true, the next time you bring the vehicle to they might consider an issue in the engine module, alternator or battery as these parts can cause an under voltage condition that can cause the symptoms you describe.

Lean Mixture Or Mechanical Condition Causes Engine Ping Sound

Question 5

There is a rattling sound coming from the engine in my 2005 Cadillac SRX.  It has 125,000 miles.  I hear the sound when I accelerate.  At a stop or cruising I don’t hear it. 

I went to a repair shop where they scanned the engine computer but found no trouble codes.  A mechanic said the engine is making a ping noise.  He said the trouble might be the gasoline.  He suggested running two tanks of premium gas.  He thought that might cure the issue but the engine continues to ping.

What’s next?  R.D.F., email

Answer 5

The next step is more testing.  Ping sounds might be caused by too lean a fuel mixture.  It’s the ratio of fuel and air and not the quality or octane of the gasoline.  Your shop will need to determine if this is an issue or if there is a mechanical condition such as an excessively worn timing chain that causes the condition.  What needs repair depends on technician findings

Excessive Wear Causes Rattle Sound

Question 6

My 2011 Hyundai Elantra engine rattles.  As I accelerate the rattling begins when the tachometer reads about 1,100 rpm.  The noise continues until the tachometer reaches 1,600 rpm and then it fades away as the rpms go up. 

I went to a repair shop.  They heard the sound.  They say it is coming from the timing chain.  It needs replacement.

My car only has 102,000 miles.  Does this sound right to you?  L.D., email

Answer 6

The noise might be from the timing chain.  It’s a little premature for it to need replacement at this mileage but it is possible depending upon how the vehicle has been driven, the driving conditions and the preventive maintenance it received.

It’s also possible the camshafts are making noise as in some instances excessive wear of the camshaft bearings are capable of creating a rattling sound.  Keep your fingers crossed the timing chain is the culprit as this is the least expensive repair.

      

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 drgizmo@hotmail.com.  More information is available at www.drgizmo.ws 12/07/2015 ® DR. GIZMO © 1989 - Present