Dr. Gizmo Column

"Dr. Gizmo"
By Phil Arendt

Brake Pulsation Returns Despite Repairs  

Question 1
The brakes pulsate in my 1991 Mercedes-Benz 350 SDL.  This has been going on for about three years.  About every six months the pulsation returns.  When this happens I take the rotors to a machine shop to have them resurfaced.   The last time this happened I replaced the rear brake pads and rotors because they were worn out.  The front brake pads were fine but the rotors were resurfaced. 

It’s been about six months since the last time the brakes needed work and the pulsation has returned.  Is there anything you can suggest that will prevent the brakes from pulsating? K.B., email

 

Answer 1

Brake pulsation is annoying and impairs brake performance.

Make sure the calipers at all four wheels have free movement and not seized.  That goes for the hydraulic pistons, too.  If there are any issues with the calipers such as sticky slides or seized pins replace parts as needed.

When tightening the lugs on the wheels, make sure to tighten them in the proper sequence and torque.  Also, make sure all wheels are straight and true.  A bent wheel can bend the brake rotors. 

Additionally, if you are using aftermarket pads and rotors consider using Mercedes-Benz original equipment parts.

Also, since driving habits can cause the brakes to overheat, time stops.  If you ride the brakes or apply the brakes with your left foot kick the habit and only use your right foot.

 

No Need For Air Bags That Shoot Shrapnel

Question 2
I’m curious about what your opinion might be on the current airbag fiasco.  The news media picks up on it here and there.  Then they go quiet for a while then they pick up on it again.  Apparently airbag manufacturer Takata is stonewalling on replacing millions of potentially dangerous airbags which could be understandable considering the difficulty and expense.  It is obvious that new cars are selling briskly and people are driving used ones with the potentially dangerous airbags on board.  When I asked a few friends about their cars what they think, they shrug their shoulders and say I don't know.  I have an older car that is not on the recall, at least at this point, but someday I will need a new one. 

I have seen on the news that people can be injured in a minor accident even if the bags are defect free.  Is it difficult or even legal to have the airbags disconnected?  R.H. Johnsburg, IL

Answer 2

Air bags that produce shrapnel should be recalled and replaced.  The company that produced them should bear the cost of replacement.  Be this as it may, it takes time to recall millions of vehicles.  It also takes time to manufacture replacement parts for millions of vehicles.  It also takes time to find all the affected vehicles and schedule them for repair. 

Not all models of affected brands are being recalled.  Affected brands include Acura, BMW, Chrysler, Dodge, Ford, Honda, Infiniti, Lexus, Mazda, Mitsubishi, Nissan, Pontiac, Saab, Subaru and Toyota.  If your vehicle is affected by this recall you should receive a notice in the mail.  You also may contact your dealership to learn if your car is affected.

As for people being injured by air bags in minor collisions, certainly if a person is hit by shrapnel injuries can be severe.  Injuries such as bruises can occur from air bags that perform normally.  Bruises are much less serious than a cracked skull, broken ribs or sternum when hitting the steering wheel, dash or windshield.  Air bags are proven to save lives and prevent serious injuries.

As for disabling the air bag system, you might consider it, but I strongly suggest that you don’t.  And you won’t find a reputable shop that will do it for you if your car is not affected by this recall.  In some cases a dealer will disable the air bag system in a recall affected vehicle if replacement parts are not available.  They also will place a warning on the dash stating that an occupant should not sit in that position until repairs are completed.

 

Warranty Won’t Pay For Oil Consumption Problem

Question 3
Dr. Gizmo, I have a 2010 Acura TLX with 117,000 miles and an extended warranty that will expire at 120,000 miles.  Over the past 20,000 miles the oil indicator light has come on prior to the oil change reminder and I have changed and added oil early.  There is no observable leak.  I am now on my third oil consumption test with my dealer.  The last test showed the engine consumed three quarters of a quart of oil in 1,000 miles.  My dealer says that unless it uses one quart per 1,000 miles my warranty will not cover the cost to further diagnose.  I need to front the money to tear down the engine to determine cause.  If the cause is located and found to be a component, my warranty will reimburse all costs.

The car is running fine other than I have also seen a five to ten percent drop in gas mileage over the past six months.  I am running out of time and seek your advice.  Thank you.  V.R., Cary, IL

Answer 3

I have not read your warranty policy so I am not aware of the terms and conditions, but your extended warranty company sets the rules.  If they require tests to confirm oil consumption is a quart consumed in 1,000 miles the test must prove to them that the engine is using excessive oil specified in their guidelines.  Your dealer also must perform the tests as specified by the warranty company.  Since tests have not confirmed excessive consumption per your warranty company guidelines they want you to pay money up front to find a failed part within the engine.  If a failed part that is covered by your warranty policy is the cause of the condition, the warranty company will pay for the repair.  This is where it gets tricky.  Wear of a component that is caused by a lack of regular and frequent preventive maintenance in contracts I have read are not covered by extended warranties or factory warranties so be sure to provide a complete service history to prove that all required preventive maintenance has been performed.  Also, since you say that the engine oil indicator light turned on indicating a low oil level, the warranty company might decline repairs because you were not diligent in checking and maintaining a proper oil level.  This may have caused damage that has resulted in oil consumption that will be found once the engine is disassembled.      

At this time the main issue is that an oil consumption test must meet the warranty company’s criteria.  If the one quart consumed within 1,000 miles criteria is not met, they will not pay for disassembly or repairs. 

 

Cure Sought For High Idle 

Question 4
First of all, thank you for your many car remedies you have shared over the years. I have learned quite a bit through your answers on what to look for when an auto problem occurs on one of my vehicles.

My question regards my 2001 Saturn SW2 wagon with an automatic transmission and 4-cylinder engine that experiences a high idle of over 1500 rpm's as I park or when stopped at a stop light.  When stopped I need to apply heavier brake pedal pressure to keep the car from inching forward.  This occurs either on a short or longer drive and the car is warmed up.  Also, this problem occurs using the A/C or heater.

I have had the car to my local repair shop but the problem does not occur for them.  No system codes are in evidence and the check engine light does not illuminate.  They have had it overnight and have driven it around town.

I am the original owner of this 90,000 mile car and have maintained it per the owner’s manual from the day it was new.  I experience no other problems with my Saturn and expect to keep it for several more years as it is in fine shape.  What do you suggest?  Thanks very much.  K.S., Algonquin, IL.

Answer 4

I’m not sure which engine is in your Saturn as two different 4-cylinder engines were available.  Be this as it may, it is likely that your car is equipped with an idle up feature when the air conditioner or defroster is active.  It’s also possible the engine is programmed to idle faster when steering especially when parking.  These are normal actions that occur when there is an additional load on the engine.  Having said this 1,500 plus rpm is excessive.

The trouble is that your shop does not experience the condition.  They cannot repair something they do not experience.  The next time you visit the shop show the condition to them.  In doing so, they will have a better understanding of the condition and possible causes.

Sometimes faulty pressure sensors in the steering and air conditioning cause this issue.  It’s also possible the engine computer has a fault or needs reprogramming as it in conjunction with sensors and actuators control the idle speed.  It’s also possible a dirty throttle body or air flow sensor is at the root of the condition.  Additionally, sometimes an issue such as this is caused by a clogged positive crankcase ventilation valve or failing thermostat or temperature sensor.

Once your shop experiences the condition they likely will perform tests on individual components to determine if they are operating as designed.  Repair all depends upon technician findings.

 

Reader Scrutinizes Dr. Gizmo’s Answer 

Question 5
I always read your column.  Recently, a reader wrote of a 2005 Hyundai running poorly after a timing belt replacement.  Having done several timing belt replacements, the most critical aspect of the project is the correct positioning of the cam and crankshaft gears when the belt is placed.  If the gears are misaligned the idle speed will either increase or retard due to the engine being out-of-time.

Your suggestion that the owner could have a throttle body problem seems misguided.  What does the fuel system have to do with a timing belt replacement?  Also, in my experience the timing belt is located in a dry area free of oil, fuel, coolant, vacuum and not influenced by a gasket leak.  S.G., Hudson, Wis.

Answer 5

Thank you for bringing this to my attention.  You are on the ball and the loveable Dr. Gizmo may agree to disagree.  In the description provided by the reader he stated that the timing belt was replaced six months prior and the condition did not begin until recently.  Certainly an improperly installed timing belt would cause idle and performance troubles immediately after the work but because the idle and performance issues manifested long after the belt was replaced I suggested other measures.  Of course it is possible that there is a fault that has recently developed in the timing belt system that presently causes trouble.  Besides fuel system issues a shop should consider there might be something amiss in the timing belt that might need attention such as a failed guide that could cause the belt to jump and cause all the engine ills.

 

Engine Cooling Fans Afflicted By Poor Ground Circuit

Question 6
I have a 2000 Pontiac Grand Prix with a 3.1 engine with cooling fans that do not turn on.  I’m not too concerned about this due to winter’s cold but when spring arrives I don’t want the engine to overheat.  I went to a repair shop where they are able to turn on the fans with a scanner but they do not know why they are not turning on without the scanner.  They replaced the fans but this did not cure the trouble.  They say the system is working backwards.  They are not sure why and think the engine computer is the cause of the trouble but they don’t want to replace it unless they are sure.  Have you seen anything like this before?  S.B., email

Answer 6

I have.  In similar instances, a poor ground condition was the problem.  Perhaps your shop should check ground connections for corrosion, security or open ground circuit.            

Thanks 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.  01/05/2015 ® DR. GIZMO © 1989 - Present