Ford: Ford Taurus Brakes, ford taurus gl, glass soda bottle

Question
Hi Ragu ,

My problem with my 93 Ford Taurus GL , 3.0  engine , 127.000 mls    (no ABS )           

before I did this  everything was fine, but after I changed the brake fluid and put Prestone Dot 4 in because  of  higher boiling point . After that it felt that there is only half the brake power. Car brakes but pedal goes down to the floor. Found in the repair manual to use only
Dot 3.            Sorry , my mistake .

Why ?  is DOT 4  fluid  different ?   can it cause damage ?

I flushed the system again and put  Prestone Dot 3 in ….still the same !   
I know from my experience as a former car mechanic ( long time ago )  that from pumping a lot the master cylinder can go bad . Put a new master cylinder in ( and did the bench bleeding )….bled the brake system again ( diagonal ) as it says in the manual . There are no leaks, system is tight, put in new front calipers and pads,checked rear brake shoes there are fine.
I bled the brakes again for the third time with Prestone DOT 3 ,no difference.

  Is it possible that there is still air in the system  ?    or can it be the pressure valve ?
   Hope you have a explanation.
Regards and Thanks
Michael


Answer
Michael first make sure that the rear brakes are adj. were they start to touch. then get your self a glass soda bottle and a 1-1/2 foot of vacumm hose what you are going to do is bottle bleed ..this is the best way to bleed any brake sys.fill the bottle with 1/4 of brake fluid now starting with the rt rear wheel brake the bleeder loosen and put the 5/16 or 1/4 vacumm hose over the bleeder and place the other end of the hose in the fluid do not let or pull the hose out till you go on to the next one .now pump the pedal till the bubbles stop coming out .do not touch the bleeder till you are done .and dot 4 is fine. do in order rt rear ,lf rear ,rt front ,lf front, keep filling the master cyl up don't let it get low....GOOD LUCK