Hi Tony,
Buick Reatta has the same brakes the TC has, and they have a better Computer Brake Page so,go to
www.reatta.net/brakes click on brake troubleshooting print out the 4 or 5 pages and take the 15 min. to run the diagnostics .
then ask..
The guys are correct.. Replace the accumulator (They are supposed to be replaced about every 5 years..
Bleed and flush the brakes with DOT-3 fluid (some have used DOT-4 )the brakes should be flushed every 2-3 years.
Remove rear wheels, Check condition of brake pads, replace if neccessary, break loose rear bleeders, then close them again. pump brake pedal 20-25 times, check fluid level (fill to mark on reservior..Close cap tightly, Use something or someone to push and hold down brake pedal, turn on key, open bleeder let fluid run till clear close bleeder. turn off key pump pedal 20-25 times fill reservior, tighten cap, turn key, push pedal down & hold down open other bleeder, run till fluid runs clear. close bleeder, put on rear wheels, go to front, pull wheels, check pads and replace if necessary, open & close bleeders, bleed front wheels as a normal car 1 side at a time till fluid runs clear. remember to pump pedal 20-25 times before opening fluid reservior, and close cap tightly.
Now run the Buick Reatta Tests again.