Jim Grant's Tech Tips
'88 Toyota Supra, Variable Brakes.
The brakes on my 88
Toyota Supra seem to need more pressure on the pedal as the car heats
up. On the first few stops, the brakes feel fine. As I drive, the more
I use the brakes, the harder I find myself depressing the pedal. It feels
like the pads are not stopping, or losing their stopping power after a
little distance. Also, the pedal gets stiffer and harder to press as the
problem progresses. I have replaced every component of the braking system
except the actual brake lines that run the length of the car, everything
from the master cylinder, booster and proportion valve to the calipers,
rotors and brake hoses at all four wheels. The problem persists.
Check the vacuum supply
hose to your vehicles power brake booster. With age and oil contamination
the vacuum supply hose can become soft. Soft to the point that, when warm,
the hose collapses. When this happens the vacuum supply to the power brake
booster is reduced or even blocked. With little to no vacuum being supplied
the brake pedal gets real hard to push. Instead of just pushing with your
big toe to stop the vehicle, it takes both feet firmly planted on the
brake pedal to get a response. Ill bet a coffee that you have a
vacuum supply problem.