Weird brake fade

[Datsun fan]

Hi guys here is the problem :

The car is '77 Mazda pickup ( front disks , back drums) and the problem appears as follows :

I start the car , try the brake pedal many times and it seems pretty good , drive the car in downtown for about 30 minutes , the brake pedal becomes very low and the brake becomes very weak!!! Then I stop the car and try the handbrake until it locks , Oh its damn weak although there is some resistance in the handbrake lever , I check For abnormal temperature in drums, disks, brake fluid , Also I checked several times brake booster and its linkage to engine , air in brake linkages , disks , Drums : installation , play, pistons and settings , springs , handbrake linkages and settings . The only thing is both drums inside are slightly machined < 0.5 mm and there are some moderate tracks on the inside of them . I tried to change pads and shoes many times , change fluid

[Datsun fan]

OK, headlights aiming is complete ! What about the main problem ? this is really pain in the ass

[Jesse C.]

Sounds to me like your brake booster has gone bad. Do you have access to gear for checking vacum?

[I'm BLUE]

Question: What do you mean "The only thing is both drums inside are slightly machined < 0.5 mm and there are some moderate tracks on the inside of them" ? Can you Clarify this and explain with pictures maybe ?

 

DO THIS FIRST:--- Fill a cup with water ( a disposable or one you will never drink out of ) , obtain a sample of brake fluid from front and rear resevoirs of your brake master cylinder. One at a time drop in a few drops of brake fluid for each sample, if the fluid floats you have water/moisture in your system , and if you have moisture in your system you need to carefully look for leaks everywhere even signs of wet spots or "dark" areas. If system is dry , bleed your trucks brake fluid system starting at the passenger side rear wheel ( open up bleeder valve and let gravity drip it out , make sure part being bleed is lowest point or close to ) , then bleed drivers side rear wheel , then bleed passenger front side wheel , then finally bleed drivers side wheel. This is a cheap quick way to replace suspected moisturized fluid that has lowered the boiling point because it has been contaminated !

 

(1) Are Your Drums Cracked

(2) Are Your Shoes/Pads Glazed ?

(3) How many times have your Drums/Rotors been Machined ?

(4) Are your Drums/Rotors within Mazda Factory Specs ?

(5) Have you tested your Brake Booster With a "known good brake booster" ?

(6) Have you checked your proportioning valve ?

(7) Are you sure they are the correct shoes/pads for the vehicle ?

(8) Is this a problem that occured slowly over an amount of time ?

(9) Is this a problem that occured shortly after working on vehicle ?

(10) HAve you Adjusted your rear brake shoes properly ?

(11) Wheel Cylinders can fail/freeze/or stick without notice ? DOUBLE CHECK THESE ?

(12) Brake Master Cylinders Can Fail , AND NOT SHOW EXTERNAL SIGNS OF LEAKAGE ?

(13) Are you having to add Brake Fluid Quite Frequently ?

(14) Do you notice any , any at all wet material around the Brake Master Cylinder or Brake Booster in the engine compartment ?

 

IT IS IMPORTANT IN NORTH AMERICA TO BLEED OUR BRAKES 1 time PER YEAR ! Have you bleed or changed the fluid in your brakes recently ? If not , boiling point goes down , and brakes can fail ! This also eats at your system , seals , and clogs brake lines with debris.

 

Jesse C. is right on the money ! Brake Boosters can slowly leak , causing loss of much needed pressure but still retain some to park/lightly stop vehicle or none at all , to Brake Master Cylinder , this makes it difficult to stop , but can still feel spungy. Make sure you check all vaccum source lines from engine , and test the check valve that goes from the engine vaccum line to the brake booster.

 

SUSPECT THE BRAKE MASTER CYLINDER OR BRAKE BOOSTER AFTER CONFIRMING ALL WHEEL CYLINDER SEALS IN REAR ARE GOOD , NOT FROZEN , AND ALL FRONT BRAKE CALIPER WHEEL CYLINDERS ARE GOOD NOT FROZEN AND NOTHING IS LEAKING ! Hopefully you have access to a mityvac vaccum gun to hold pressure in order to see if the diaphram in the brake booster is leaking ! If you already have bled your brakes , and notice the fluid collecting black at the bottom but rest is clear most likely your brake master cylinder has given out ! ( hard to tell you have to know what you are looking for )

 

Get back to us so we can help !

 

DTP

[I'm BLUE]

Ohhh forgot to mention if you replace the brake master cylinder , do not forget to bench bleed it before installing or there will be a much higher risk of blowing out the seals/stuck air bubbles.

[I'm BLUE]

Question(s)

 

When is the last time your Front Disc Brake Calipers/ Rear Brake Wheel Cylinders were replaced by chance ?

 

Has your Brake Booster or Brake Master Cylinder ever been replaced ?

 

Just a thought ! Good Luck Friend !

[Datsun fan]

Thnx man for the comprehensive reply , I really appreciate that .

Question: What do you mean "The only thing is both drums inside are slightly machined < 0.5 mm and there are some moderate tracks on the inside of them" ? Can you Clarify this and explain with pictures maybe ?

Answer: They possibly got warped in the past and became out of round and former owner of that truck took them to a lathe to make them round again by "wiping" their inner surfaces , Now the difference between inner diameter of drums I've and stock drums is about 1 mm ( I don't remember exact # ) besides some inner surface LINES OR STRIPES OR TRACKS or whatever .

 

The brake fluid has been changed entirely 3 times 2 months ago and were NOT

Moisturized/contaminated , visual inspection and air pressure test indicate a leak-free brake lines/joints .

 

(1) Are Your Drums Cracked? No

(2) Are Your Shoes/Pads Glazed ? Didn't understand

(3) How many times have your Drums/Rotors been Machined ? Drums = ? , Rotors = 0

4) Are your Drums/Rotors within Mazda Factory Specs ? Yes

(5) Have you tested your Brake Booster With a "known good brake booster" ? No

(6) Have you checked your proportioning valve ? There is no proportioning valve/Bias valve in this truck .

(7) Are you sure they are the correct shoes/pads for the vehicle ? Yes

(8) Is this a problem that occurred slowly over an amount of time ? No

(9) Is this a problem that occurred shortly after working on vehicle ? Yes, After rebuilding and installing rear shoes .

(10) Have you Adjusted your rear brake shoes properly ? Yes, Many times

11) Wheel Cylinders can fail/freeze/or stick without notice ? DOUBLE CHECK THESE ? Yes, Many times .

12) Brake Master Cylinders Can Fail , AND NOT SHOW EXTERNAL SIGNS OF LEAKAGE ? Has been already checked by Mazda certified mechanic .

13) Are you having to add Brake Fluid Quite Frequently ? No

14) Do you notice any , any at all wet material around the Brake Master Cylinder or Brake Booster in the engine compartment ? No

 

IT IS IMPORTANT IN NORTH AMERICA TO BLEED OUR BRAKES 1 time PER YEAR ! Have you bleed or changed the fluid in your brakes recently ? Yes, DOT 4 as recommended .

 

Make sure you check all vacuum source lines from engine , and test the check valve that goes from the engine vacuum line to the brake booster…………. ALREADY DONE !

 

The BRAKE MASTER CYLINDER OR BRAKE BOOSTER are good and ALL WHEEL CYLINDER SEALS IN REAR ARE GOOD , NOT FROZEN , AND ALL FRONT BRAKE CALIPER WHEEL CYLINDERS ARE GOOD NOT FROZEN AND NOTHING IS LEAKING .

I don't have access to a mityvac vacuum gun to hold pressure in order to see if the diaphragm in the brake booster is leaking !

 

(15) When is the last time your Front Disc Brake Calipers/ Rear Brake Wheel Cylinders were replaced by chance ? 3 years ago .

(16) Has your Brake Booster or Brake Master Cylinder ever been replaced ?

Brake Booster: 1 year ago, Brake Master Cylinder: I don't know .

 

And now let me describe the situation accurately

The serious brake fade problem seems to be (come and go) problem, not driving period or temperature. This problem is accompanied with synchronized handbrake fade (also come and go) and this makes it more serious . At the 4 wheel bleeders the fluid pressure seems pretty good, which makes it really weird .

Maybe I should try to change the driver........hehehehe .

Waiting for updates .

[I'm BLUE]

Hey Datsun Fan !

 

Maybe I should try to change the driver........hehehehe .

 

Well if you change the driver of my vehicle a lot of problems should be solved !

 

And now let me describe the situation accurately

The serious brake fade problem seems to be (come and go) problem, not driving period or temperature. This problem is accompanied with synchronized handbrake fade (also come and go) and this makes it more serious . At the 4 wheel bleeders the fluid pressure seems pretty good, which makes it really weird .

 

Ok , sorry about that I thought you reffering to a driving pressure fade problem. Now I understand it is soley/only to do with your handbrake/park brake application fades out ! I have a 1990 Ford Ranger Pickup , as you know Mazda's and Fords about 1990 and up years are basically the same engineeering. There are weakpoints on my truck as well as other turds I mean ford's

 

(1) Rear Drum Brake Self Adjusting Start Wheels at the bottom SEIZE UP !!! What this means for you and I is instead of the idea of it SELF ADJUSTING THE BRAKE SHOES OUT TO A SPECIFIED DISTANCE , the further , and longer it is sezied as well as the more your brake shoes wear in the worse , or weaker your parking brake will feel. It will still work , but not any where near where it is suppose to !

 

(2) Recently I had to adjust my parking brake cable assembly that lines under the cab , get a buddy , get some wrenches , and slowy in increments tighten/loosen parking brake cable assembly under the drivers cab/chasis ( not at the rear by the drums ) and have your buddy test the "tightness" or "feel" of the assembly while engaging and disengaging ( you can do this yourself but goes a lot quicker with a friend helping you ! IMPORTANT NOTE : FORD pickups are known to have issues with stretching or cracking the plastic insulation of the actual parking brake cable , thus causing a distance issue or adjustment issue since the plastic is what the cable/assembly is holding tension against as an adjuster ( look for cracks , wear , or tears on the black plastic parts of the cables. )

 

(3) Is your parking brake adjustment inside the cab bent , loose , out of adjustment or broken by chance ( another problem with turds , I mean fords ) ? ( Sorry not to sound demeaning I actual had the throttle cable bracket rip off the firewall on me one morning on my friends explorer) Parts can wallow out or wear out without being able to see until pulled out for inspection.

 

Recommendations

 

(1) Take Off/ Inspect rear adjusting star wheel located usually at the bottom between the rear brake shoes , should spin freely and easily if not replace , and re-adust.

(2) Check all brake hardware ( springs , pins , retaining springs , adjuster ) Asking self the last time this stuff was replaced when inspecting ( sometimes old , even new cheap hardware can fail/fall apart or just not work )

(3) Adjust the Parking Brake Cable Assembly Under Cab/Chasis usually towards middle of chasis , and tighten/adjust/inspect cable for cracks , frays or tears with a friend.

 

 

I wish I was there to help , I love doing brake work ! :lol:

 

Ok , Good Luck , and I apologize for the length in Advance ! ( I hope you are not drifting the truck ? :lol::lol::lol: :cool: )

 

DTP

 

P.S ( by my writeup , Basically everything with Ford's goes wrong , HA HA HA :lol::lol::lol: )

Edited December 18, 2009 by DTP

[Datsun fan]

" If system is dry , bleed your trucks brake fluid system starting at the passenger side rear wheel ( open up bleeder valve and let gravity drip it out , make sure part being bleed is lowest point or close to ) , then bleed drivers side rear wheel , then bleed passenger front side wheel , then finally bleed drivers side wheel. "

So I did the bleeding process a week ago according to DTP and DAMNED ........... there

was air coming out from the 4 bleeder valves ..... Now the brake is working pretty good .

thanks DTP your reply really helped a lot.

 

Always suspect details first .

 

Weird brake and handbrake fade are history . Brake job is complete .

[I'm BLUE]

" If system is dry , bleed your trucks brake fluid system starting at the passenger side rear wheel ( open up bleeder valve and let gravity drip it out , make sure part being bleed is lowest point or close to ) , then bleed drivers side rear wheel , then bleed passenger front side wheel , then finally bleed drivers side wheel. "

So I did the bleeding process a week ago according to DTP and DAMNED ........... there

was air coming out from the 4 bleeder valves ..... Now the brake is working pretty good .

thanks DTP your reply really helped a lot.

 

Always suspect details first .

 

Weird brake and handbrake fade are history . Brake job is complete .

 

Very Cool ! I could tell you knew what you were doing on your truck , so it only made sense that it was a little thing like ya said ! :cool: That's gotta be a huge relief for you ? ( especially on brakes :lol: ) I am absolutely stoked to hear that , and it sounds like you have all your brake parts replaced to last a very long time my friend ! ( I like to bleed the brakes 1 time per year , just to keep moisture/other crap in the system out , and same with clutch master/slave cylinder fluid :cool: Changing your anti-freeze every 2 will actually help a lot with life of gaskets and life of the water pump too since anti-freeze in the U.S contains water pump lubricant too:cool: ! I change my oil no more than 3,000 miles ( I don't know how many kilometers that is ? )

 

Well don't be a stranger Datsun fan ! Ya gotta any pictures of the truck by chance ? ( no worries if not :cool: )