troubleshooting the brake system

[shogun]

Fault
Brakes pull to one side

Cause
a) Tyre pressure incorrect
b) Unevenly worn tire treads
c) Oil on pads/liners
d) Wrong type of pads/liners
e) Dirty floating caliper recesses
f) Guide bolts dirty or damaged
g) Rear wheel alignment adjusted incorrectly
h) Corrosion in floating calipers or wheel cylinders
i) No shock absorber action
k) Pad of one caliper worn
l) Pad glazed

Remedy
a) Correct tire pressure
b) Change or replace tyres
c) Replace brake linings, check for causes
d) Replace brake linings,check for causes
e) Remove and install/clean floating calipers
f) Replace guide bolts
g) Check wheel alignment
h) Remove and install, repair or replace floating calipers or wheel cylinders
i) Check shock absorber, replacing if necessary
k) Replace brake linings , Check floating caliper
l) Replace brake linings , Check floating caliper


Fault
Brakes excessively hot while driving

Cause
a) Vent bore in master cylinder clogged
b) No play between push rod and master cylinder piston
c) Swollen rubber parts due to use of wrong brake fluid
d) Vent bore in expansion tank clogged
e) Corroded floating calipers
f) Cross spring broken
g) Handbrake lever not released fully

Remedy
a) Overhaul master brake cylinder,replacing if necessary
b) Adjust push rod (in older cars)
c) Overhaul master brake cylinder,replacing if necessary
d) Clean expansion tank
e) Remove and install, repair or replace floating calipers
f) Replace cross spring
g) Check handbrake and handbrake cables ,repair if necessary

Fault
Poor braking effect in spite of great force on pedal
Brake-pedal travel normal

Cause
Brake pads oil-splattered or burnt; wrong type of brake pads

Remedy
Replace brake linings

Fault
Poor braking effect in spite of great force on pedal
Brake-pedal travel short

Cause
Brake booster malfunctions - engine vacuum

Remedy
Check brake booster system
- Check engine (valves, cylinder head gasket etc.)

Fault
Poor braking effect in spite of great force on pedal
Brake-pedal travel long

Cause
One brake circuit failed due to leaks or damage

Remedy
Leakage test of brake system

Fault
Brake pedal can be pressed down softly and springily

Cause
a) Air in braking system
b) Insufficient brake fluid in expansion tank - refer to a)
c) Overheated brake fluid - vapour lock due to excessive water content in brake fluid or excessive brake loads

Remedy
a) Top up or change brake fluid
Bleed brakes
b) Top up or change brake fluid
Bleed brakes
c) Top up or change brake fluid
Bleed brakes

Fault
Brake is bled and readjusted, but brake pedal can be pressed down too far

Cause
a) Primary cup in master cylinder damaged
b) Separating cups on floating piston of tandem-brake master cylinder leak
c) Leak in braking system

Remedy
a) Overhaul or replace brake master cylinder
b) Overhaul or replace brake master cylinder
c) Leakage test of brake system

Fault
Uneven pad wear

Cause
a) Wrong type of pads/liners
b) Dirty fist caliper recesses, damaged caps
c) Corrosion in floating calipers or wheel cylinders
d) Swollen rubber ring for piston control

Remedy
a) Replace brake linings
b) Remove and install, repair or replace floating calipers or wheel cylinders
c) Remove and install, repair or replace floating calipers or wheel cylinders
d) Remove and install, repair or replace floating calipers or wheel cylinders

Fault
Brake pads worn at angle

Cause
a) Wheel-bearing play excessive
b) Brake disc not aligned with fist caliper
c) Corrosion in floating calipers or wheel cylinders
d) Angular brake-disc wear
e) Pads worn to less than minimum thickness
f) Spring force insufficient
g) Guide bolts damaged

Remedy
a) Replace wheel bearings
b) Check floating caliper installation
c) Remove and install, repair or replace floating calipers or wheel cylinders
d) Grind or replace brake discs
e) Replace brake linings
f) Replace spring
g) Replace guide bolts

Fault
Seized brake pads, pad does not move off brake disc

Cause
a) Dirty fist caliper recesses, damaged caps
b) Corrosion in floating calipers
c) Vent bore in master cylinder clogged

Remedy
a) Remove and install, repair or replace floating calipers
b) Remove and install, repair or replace floating calipers
c) Overhaul or replace brake master cylinder

Fault
Brakes squeal or rattle

Cause
a) Wrong type of pads/liners
b) Dirty floating caliper recesses
c) Spring force insufficient
d) Brake disc not aligned with fist caliper
e) Brake-disc runout
f) Excessive thickness deviation within braking surface
g) Brake drums eccentric
h) Knocking brake drums
i) Dirt and dust in brake drums
k) Liner wear excessive or one-sided
l) Rust edges on brake discs
m) Pad loose
n) Wheel-bearing play excessive

Remedy
a) Replace brake linings
b) Remove and install/clean floating calipers
c) Replace spring
d) Check floating caliper installation
e) Check brake discs for runout, replacing if necessary
f) Measure brake disc thickness
Grind or replace discs
g) Grind or replace brake drums
h) Grind or replace brake drums
i) Clean and check brake drums
k) Replace brake shoes
l) Grind or replace brake discs
m) Replace brake linings
n) Replace wheel bearings

Fault
Brake-pedal dead travel excessive

Cause
a) Wheel-bearing play excessive
b) Brake disc not aligned with fist caliper
c) Brake-disc runout
d) Excessive thickness deviation within braking surface
e) Brake system leaky
f) Air in braking system
g) Wrong type of pads/liners
h) Automatic slack control of brake shoes does not function

Remedy
a) Replace wheel bearings
b) Check floating caliper installation
c) Check brake discs for runout, replacing if necessary
d) Measure brake disc thickness - Grind or replace discs
e) Leakage test of brake system
f) Bleed brakes
g) Replace brake linings or Replace brake shoes
h) Remove and install brake shoes , repair slack control

Fault
Jammed piston in brake caliper

Cause
a) Dirty fist caliper recesses, damaged caps
b) Brake disc not aligned with fist caliper
c) Corrosion on pistons in floating calipers or wheel cylinders

Remedy
a) Remove and install, repair or replace floating caliper
b) Check floating caliper installation
c) Remove and install, repair or replace floating caliper or wheel cylinder

Fault
Pulsating effect on brake pedal

Cause
) Wheel-bearing play excessive
b) Brake disc not aligned with fist caliper
c) Brake-disc runout
d) Excessive thickness deviation within braking surface

Remedy
a) Replace wheel bearings
b) Check floating caliper installation
c) Replace brake discs
d) Measure brake disc thickness
Grind or replace discs

Fault
Handbrake effect insufficient

Cause
a) Brake shoes oil-splattered
b) Excessive dead travel between brake shoes and brake drums
c) Excessive dead travel in cables
d) Cables adjusted incorrectly
e) Corroded transmitting elements

Remedy
a) Replace brake linings, determine cause
b) Adjusting handbrake
c) Adjusting handbrake
d) Adjusting handbrake
e) Remove and install handbrake and expander locks
Check Bowden cables, replacing if necessary

source: http://tis.spaghetticoder.org/

[freddybeemer100]

I had an old Continental tire which pulled to one side. After flushing and power bleeding the brakes, the problem remained. I changed the tire and voila! Problem solved.

I am a firm believer of rebuilding and replacing every brake part at the first sign of trouble. Old bad fluid contains moisture which can boil under high heat conditions as well as corrode the calipers locking them in their bores. Ask 80's Vette owners.

[lasmariaspr]

Source has some really great info, very helpful. Nice find shogun, I will be adding this one to my bookmarks.

[shogun]

That problem with the old tire I can confirm from own experience.

Also the point to change brake fluid at least every 2 years is very important.
BMW used to recommend one-year brake fluid changes (now every two as calculated on OBC on newer BMW).

Alternative BMW Maintenance Schedule

Enhanced Maintenance Schedule by Mike Miller of Bimmer and Roundel magazines

BMW’s Free Scheduled Maintenance program means that BMW will perform scheduled maintenance free of charge during the BMW New Vehicle Limited Warranty period.

Prior to the advent of BMW Free Scheduled Maintenance, approximate BMW maintenance recommendations were: automatic transmission fluid (ATF) and filter changes every 15,000 miles, manual gearbox and differential oil changes every 30,000 miles, annual brake fluid changes, and coolant changes every two years. Spark plugs, air filter, and fuel filters were typically replaced every 30,000 miles on most BMWs (this is a tune-up) except M cars up to 1995, which got new spark plugs and a valve adjustment every 15,000. Later advances in computer engine management and spark plug technology legitimately allow 60,000-mile spark plug life if not more.

Prior to Free Scheduled Maintenance, you couldn’t change engine oil often enough according to most dealerships. And when the car was in the shop it would often be due for this service or that inspection, all at the owner’s expense.

But once BMW began paying for scheduled maintenance, lo and behold the “schedule” was revised. Now, magically, the cars hardly need any maintenance at all! The 1,200-mile break-in service was done away with except for M cars. Engine oil suddenly lasts 15,000 miles (dealers are supposed to use BMW synthetic oil). Manual gearbox and differential oil? No worries there – now BMW says they NEVER need to be changed, it’s “lifetime fill.” Brake fluid and coolant service intervals were doubled with no change in the original BMW brake fluid and anti-freeze dealers are supposed to use.

So, is Free Scheduled Maintenance all about marketing and cost reduction – BMW’s costs? Draw your own conclusions. There is no doubt that many buyers incorrectly view BMWs as “high maintenance” cars. Nothing can address that more effectively than Free Scheduled Maintenance. But the operative word in the name is “scheduled.” In my opinion, extended service intervals and “lifetime fill” came very close on the heels of Free Scheduled Maintenance.

This is an alternative to BMW’s factory-recommended maintenance schedule. It is not, “Mike Miller’s maintenance schedule.” It is actually BMW’s maintenance schedule, more or less, which was used prior to Free Scheduled Maintenance. It also represents my opinion, based upon my experience and that of my readers, tech advisors, and professional BMW technicians both dealer and independent. I have prepared it because of the large number of readers asking for this information. The fact that my opinions may differ from those of others does not mean anyone is necessarily right or wrong. You will get a different answer from every person you ask about routine vehicle maintenance.

You should also know that in my work I have observed the most common reason for BMW drivability problems in contemporary cars with over 100,000 miles is that they need a tune up – spark plugs, air filter, and fuel filter.
http://blog.avusautosport.com/2009/10/mike-miller-alternative-maintenance-schedule/

Brake Fluid

Recommend one-year brake fluid changes, or prior to each driving school or track event. BMW now recommends two-year brake fluid changes, but used to recommend a one-year interval.

Recommend ATE SL brake fluid for normal street use, ATE Type 200 or Pentosin Racing Brake Fluid for track work or very high performance use