89 Honda Accord 2 Door 5 spd.. Major brake pedal fade when outdoor temperature is above 80 degrees F

89 Honda Accord 2 Door 5 spd.. Major brake pedal fade when outdoor
temperature is above 80 degrees F. No leaks and fluid has been
change/blead.

The higher the temperature the faster the fade is. The pedal will fade
slowly when braking or stopped while holding the pedal down. If held
long enough it will bottom out but still have braking pressure.
Definitely not solid enough. Below 80 degrees F. the pedal becomes
firmer as temperature drops. Very strange I have never had brakes act
like that. I speculate it is the Power Brake Booster? Anyone have
experience with this problem? Thanks

 

Seals in your master cylinder are worn out . Time to replace the master
cylinder, and bleed the brakes. bob

 

This isn't what we usually call fade, which is loss of stopping power with a
normal or hard pedal - it is usually called a falling brake pedal. It isn't
the booster - that can make the pedal hard but can't make it fall. The most
likely cause - especially if it isn't consuming brake fluid - is the master
cylinder. Rebuilding it is inexpensive (but check on prices of exchange
master cylinders - they can be very cost-effective) and replacement is a
medium DIY job. If you did the brake bleed you will certainly be ready for
the master cylinder.

Mike

 

Exact same problem with my 91 Accord, replace master cylinder and the
problem will disappear.

 

Ok now I uderstand. The master cylinder's primary seal is weak and the
secondary seal is still good so it hasn't started to leak fluid.
Thanks for helping me know exactly what it is. I have rebuilt or
replaced master cylinder,calipers & rear brake cylinders but they were
always leaking fluid so I knew what the problem was. Thanks again