122-L9R2T-03

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Advanced Technical Information
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1801 4636
Brake Squeal
Binder - Advanced Technical Information
This bulletin replaces bulletin Group 4,
#1605, dated 03/24/2016.
Attention:		 Service Managers/Service Technicians
Vehicle Type: 		
All
Model Year: 		
All
Concern:		
Customer reports that vehicle brakes squeal.
Information:		Remember that brake squeal is a normal result of different factors acting upon the brake system
and does not constitute a defect.
			
• Normal brake noises, such as squeal, occur under a narrow set of operating condition.
				
• An example would be low speed, light brake pedal application.
			
• Abnormal brake noises occur under wider operating conditions. 						
• An example would be during light or heavy braking at any speed or temperature
			In the interest of customer satisfaction, we will perform a brake inspection to assure the customer
that there are no safety or performance issues associated with brake noise. Porsche will cover this
inspection under warranty.
			The customer may also refer to the owner’s manual section on Driving and Driving Safety regarding
brake squeal.
			Disclaimer
			Porsche vehicles have high performance brake systems. Due to the stresses to which Porsche
vehicles are oftentimes subjected, Porsche vehicles presented for brake service may exhibit exceptional wear at earlier than expected times compared to wear found typically on other vehicles. All
the conditions described below are the result of normal brake system wear and are therefore not
warrantable.
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(cont’d):		“However, disc brake squeal remains an elusive problem, and there is not yet a method to completely suppress it.”
			
Reference: This is a book published by the Society of Automotive Engineers.
			
Disc brake squeal: Mechanism, Analysis, Evaluation, and Reduction/Prevention /[edited by] Frank 		
			
Chen, Chin An Tan, and Ronald L. Quaglia. SAE)
			www.SAE.org
			Brake Friction Materials are Different
			There is a common misconception that all brakes should exhibit the same characteristics. In the
North American Market (U.S. & Canada), one brake friction material is used more than any other is.
It is called Non Asbestos Organic (NAO). The dominance of this friction material in the market has
aided this misconception.
			The characteristics of this material are:
			
			
			
			
• Excellent Noise, Vibration, & Harshness (NVH) characteristics
• Excellent lining wear
• Produces low amounts of wheel dust
• Friction level fades at high temperature
			This list matches customer expectations pretty well. However, the last characteristic about friction
level fading at high temperature makes it unsuitable for Porsche.
			Porsche uses a Low Met friction material to meet our high performance standards. The characteristics of this material are:
			
			
			
			
			
			
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• High coefficient of friction
• Excellent fade characteristics (friction level does not fade at high temperature)
• Very effective at stopping the vehicle
• Noise can be more than other friction materials
• Wheel dust is a normal by product
• Lining life is low (compared to NAO for example)
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(cont’d):		The graph below illustrates the difference in fade characteristics between NAO & Low Met friction
materials:
			Low met performance characteristics are necessary to maintain the balance of performance in the
Porsche vehicle as a whole.
		
What is Brake Squeal?
			Brake squeal is a noise that is the result of minute vibrations. The minute vibrations occur as the rotor moves in relation to the pad. A combination of high friction levels and low pedal pressure create
ideal conditions for noise.
			
The condition that is creating the noise is called “stick-slip”.
			This stick-slip condition is most prevalent during light braking. Light braking smooths the rotor and
the pad surfaces. When this is coupled with imperfect pressure distribution on the pad (due to low
pedal pressure), the conditions for stick-slip exist. The noise occurs as the transition is made from
stick to slip.
Slip
Frequency
Velocity
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(cont’d):		Some clear indications of a normal brake squeal resulting from the conditions described are:
			
			
			
• When the squeal occurs, applying more brake pressure makes it go away
• The rotor has a polished mirror like finish on it
• The pads have a smooth surface finish, like a glaze
			Other Contributing Factors
			Other factors also contribute to brake squeal. All components (even the bolts) have what are called
“bending and twisting modes.” As force is applied to a component, it will bend and twist in different
ways. The bending and twisting modes change as brake pressure and temperature changes. As the
components are mounted together, coupling effects also become a factor.
			The amount of bending and twisting is so small as not to be visible to the naked eye. It is a normal
characteristic of all components. It is determined through Frequency Response Testing.
			This is why proper torque on fasteners is critical. Other factors include component temperature,
mass, geometry, insulation, and lubrication. Weather and driving conditions are also major factors.
,
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(cont’d):		Countermeasure Limitations
			
Brake squeal can fall into a very wide frequency range. The range is divided into three groups:
			
			
1. Low Range 1 - 3 KHz
			
2. Mid-Range 3 – 6 KHz
			
3. High Range 6 – 20 KHz (above 14KHz can be very difficult to hear)
			The frequency of the noise will determine what countermeasure to use. Some common countermeasures are listed below:
			• Pad Chamfers
			
• Various slot configurations in the pad
			• Pad slippers
			
• Shims of various types
			• Tuned mass dampers
			• Fixed calipers
			Countermeasures are limited on a given brake system due to limitations with space and performance. Testing must be performed to determine if a countermeasure is effective without deteriorating performance.
			Measuring the Noise
			Since the frequency of the noise determines the countermeasure, it is not possible to address the
issue without knowing the frequency.
			This is why it is necessary to capture the information using an FFT (Fast Fourier Transform). There
are applications for smartphones and tablets that will do this.
			
Two real life examples from Porsche vehicles are illustrated:
		
			
		
		
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(cont’d):		The base frequency shown (1550 Hz) is the noise where the problem is coming from. The other five
peaks are all harmonics. This means that if the base frequency is eliminated, the others will go away
as well.
			In a second example, we see a squeal frequency without harmonics. This frequency is over five
times higher than the last example. The countermeasure required for this noise will be completely
different from the last example.
			
As mentioned above, the apps are available for smartphones and tablets. Two apps are listed below:
			iOS
			FFT Plot
			Android
			Speedy Spectrum Analyzer
			Note: FFT plots are required for brake noise warranty cases; please refer to the procedure below.
			Procedure
			
1. Test drive with the customer to verify the noise. The customer should be able to reproduce the
noise on the test drive.
			
• This will help ensure you are addressing the same concern.
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(cont’d):		FFT Plot (Required for Warranty)
			
2. Take an FFT plot of the noise during the test drive with the customer.
			
• This is important because the frequency of the noise can vary widely
			
• The frequency helps point to the source of the noise
			
• The intensity (measured in decibels dB) helps us know how bad it is and how much we have
improved it after our work
			
• The
 plot needs to be recorded from inside the vehicle where the noise is heard by the customer.
			
• An omnidirectional microphone with a greater sensitivity can be attached to a tablet or smartphone to improve recording ability
			
3. The third step is to perform a thorough visual inspection.
			
4. Perform repair work as necessary.
			
5. A final FFT confirms that the noise has been improved or eliminated.
			Component Inspection Guidelines
			Fluid
			
Fluid replacement is required every two years by the maintenance schedule.
			
• WM 470855 Changing the brake fluid
			
• There is also a section in the Owner Maintenance booklet dedicated to recording the brake
flushes every 2 years
			
Moisture in the fluid is heavier than the fluid, and accumulates in the calipers.
			
• Moisture affects the viscosity of the fluid and its ability to lubricate
			
• Corrosion and damage to the caliper can also result
			The right rear caliper is the farthest from the reservoir and may be affected more than the other
calipers.
			
• This is due to the larger volume of fluid in that circuit and therefore a larger amount of moisture
can settle in that caliper
			
If squeal is occurring on one wheel in particular, fluid condition is likely to be a part of the problem.
			Countermeasure
			
Flushing the fluid is necessary to get rid of the moisture accumulation.
			Tip:  Warming the fluid by driving and braking before flushing it, can help get a more thorough flush
of the fluid.
			
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(cont’d):		Brake Pads
			• Glazed surface
			
• Cracks from overheating
		
• Dust buildup at edges
			
• Contamination from sprays such as tire dressings
			
• Wear at contact points
			
• Piston contact on pad shows even or uneven pressure distribution
			
• Pad to caliper contact points show how pad moves in caliper
			
• Spring to pad contact shows how well spring tensions pad
			Countermeasure
			
• Sanding the pad and chamfering the edges
			
• Insuring the contact points are smooth
			
• Lubricating contact points with optimol grease
			
• Insure proper fit and lubrication of shims and/or dampers
		
				
		
		
					
			
			
Note: Take photos as you inspect. Remember that part numbers and batch numbers must also be
readable. It is required on the PQIS job/warranty claim.
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(cont’d):		Rotos
		
• Lips develop at outer and inner edges of pad contact area
		
			• Corrosion
			
• Contamination by sprays, fluids, road salt, grime, and small particles becoming embedded between the pad and rotor
			• Glazed surface
			
Rotor Finish: The non-directional finish of a new rotor is better for noise than the polished rotor 		
resulting from light-footed braking.
			Glazed pads and rotors are the fingerprint of the normal, light-footed, slow speed brake squeal.
Replacement of the pads and rotors with the same pads and rotors that are already on the vehicle,
will not improve the situation. As the new parts are subjected to the same conditions, the squeal
will return.
			
A glazed rotor is not a safety or performance issue.
			Countermeasure
			It is not possible to sand or hone the rotor due to the possibility of introducing judder because of
imperfect sanding or honing. Altering the driving habit by using a little more pedal force is sufficient
to improve the noise.
			
NOTE: Also, remember to photograph the rotor production information for the PQIS job/Warranty
claim.
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(cont’d):		Calipers
			
• Pad Mounting Pins – witness marks indicate movement between pad and caliper pin
			Countermeasure
			• Make sure the pins are smooth first
			
• Lubricate contact points with a small amount of optimoly grease and insure proper fit of components
			Tension spring
			• M
 ovement between spring and pads will vary as spring tension varies. The witness marks will
reflect this.
			
• Push upwards on pad against spring, release the pad and you should hear a clack. Excessive stiffness or weakness in the spring is not acceptable.
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(cont’d):		Caliper Pistons
		
• Wear marks from movement of pad against piston. This is an indication of pressure distribution
from the piston to the pad. Brake squeal is affected by pressure distribution, especially at low
pedal pressures.
			
			
• Inspect pistons to see if there are any that may not be returning completely.
• Exercising the caliper pistons can restore the movement of the piston to normal operation (the
brake fluid must also be clean).
		
Exercising Brake Caliper Pistons
			• Remove brake caliper
			
• Remove pads and hardware
			
• Have the following parts on hand:
			
- Caliper paste 000.043.117.00
			
- Optimoly paste 000.043.020.00 (the 100g tube should last through several repairs)
			
- New hardware kit
			
- New dust seals
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(cont’d):
			
			
• Clean brake caliper so that there are no contaminants present when the dust seals are removed
			
			
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• Remove dust seals from the caliper pistons
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(cont’d):
		
• Extend the pistons against a block of wood to keep them from coming out of the caliper. (It may
be necessary to retract and extend the pistons several times to free up the movement)
			
• Apply brake caliper paste to the piston and install new dust seals on the pistons
			
• Retract the pistons and seat the dust seals
			
• Install pads and new hardware
			
• Install caliper on vehicle
			
• Flush brake fluid
			• Test-drive the vehicle
			
In cases where additional help is needed, please file a TLAR.
			
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Warranty			
Information:		
Warranty Coding Information
			
			
			
			
NOTE: Documentation requirements include:
• FFT plots with the frequency and dB level highlighted as in the examples given
• Clear photographs illustrating fluid condition, contact points, wear, defects or abnormalities
properly labeled according to their location
• Part number data from pads and rotors must be photographed as in the examples shown
		
			Labor Operations
			
Both labor operations below are unique labor operations that the dealer creates. They do not already
exist in the system.
			(Noise is Normal)		
			
Test Drive & Verification 47010299
35TU
			Includes:
Test drive, FFT capture, and documentation (20 minutes)
			
Labor Operations (Noise is NOT Normal)
			
Test Drive & Verification 47010399
100TU
			Includes:
Test drive, FFT capture, and documentation (20 minutes)
				
Visual inspection time with photos (10 minutes per wheel)
			The following operations are claimed separately:
			• Remove and Reinstall wheels		
			• Remove and Reinstall Front Brake Pads*
			• Remove and Reinstall Rear Brake Pads*
		
			*Includes:
Remove and Reinstall Brake Caliper (Note: New caliper bolts must be installed)
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Information		
(cont’d):		
PQIS Coding Information
		
			Part IDs
			Calipers – Front – 4739
				
Rear - 4741
			Rotors – Front – 4650 (4651 PCCB)
				
Rear - 4653 (4654 PCCB)
			
		
Pads – Front – 4636 (4634 PCCB)
Rear - 4638 (4635 PCCB)
		
Damage Codes (most common)
			3013 Damaged – Damage to brake components
			
3031 Flaked off – PCCB material separation		
			
1041 Foreign Object – Small rocks or other debris get into rotor/pad interface
			
1319 Lateral Runout – Lateral runout causing vibration
			
1417 Overheated, too hot – Rotors with bluing, pads with cracks
			
1316 Rubs – Backing plate rubs rotor or another object rubs against brake component
			
2019 Squeaks – Glazed pads/rotors, normal squeal			
			
3311 Surface Corrosion – Corrosion on rotor surface causing noise/vibration
		
Important Notice: Technical Bulletins issued by Porsche Cars North America, Inc. are intended only for use by professional automotive technicians who have attended
Porsche service training courses. They are written to inform those technicians of conditions that may occur on some Porsche vehicles, or to provide information that could
assist in the proper servicing of a vehicle. Porsche special tools may be necessary in order to perform certain operations identified in these bulletins. Use of tools and
procedures other than those Porsche recommends in these bulletins may be detrimental to the safe operation of your vehicle, and may endanger the people working on it.
Properly trained Porsche technicians have the equipment, tools, safety instructions, and know-how to do the job properly and safely. Part numbers listed in these bulletins
are for reference only. The work procedures updated electronically in the Porsche PIWIS diagnostic and testing device take precedence and, in the event of a discrepancy,
the work procedures in the PIWIS Tester are the ones that must be followed.
©2018 Porsche Cars North America, Inc.
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