99 chevy Tahoe Brake Probelms

99 Chevy Tahoe - old body style
Replaced pads front and rear
new master cylinder
new calipers
new rear brake cylinders
have bleed the brakes still not right
problem is seems not to be as firm and will go down
to almost the floor like spongy feeling yet

was told maybe still air in lines or
the rear cylinders might need to be adjusted again
any ideas sure would help
Thanks in advanced - Linda

your Tahoe is the GM OBS which has drum rear brakes. the rotors are replaced when they get chewed up or rusted . the rear drums must never be cut also after 40K miles they do require replacing. you may question my response but the fact is when a drum is cut or worn down the drum radius does not match the radius of the brake shoes. a spongy pedal would be from a worn or cut drum or air in the system which may require the master cylinder to be bled. this can happen if the fluid drops too low air can get into it. replacing those fluid parts will cause the master to get air in it and unless properly bled not good ..

I have been there Waldo a few times.

Thanks j cat- Sorry forgot to put in - did all to the rear brakes at the same time
the man said he might have to readjust the back brakes
did bench bleed the master cylinder and put on and bleed the brakes
was thinking also does antilock brakes play any part in this
read somewhere can get air bubbles there and might need to take
to a shop and do a press bleed on it
Side note now that there is no Waldo Police dept. any more don't have to watch your speed as much, good feeling there

Thanks j cat- Sorry forgot to put in - did all to the rear brakes at the same time
the man said he might have to readjust the back brakes
did bench bleed the master cylinder and put on and bleed the brakes
was thinking also does antilock brakes play any part in this
read somewhere can get air bubbles there and might need to take
to a shop and do a press bleed on it
Side note now that there is no Waldo Police dept. any more don't have to watch your speed as much, good feeling there

Sounds like he did bled properly , but it is possible he did not do it good enough.

the ABS valve body unit will not get air into it because when doing this work the ABS is off and no valves will open though it can happen. so I and others have done this, drive it on the soft shoulder of road and hit the brakes a little hard so the ABS comes on . this may push out the air and then have the brakes bled again..

JUST saying on doing this work . when I open up the brake lines I get a stick and set it to push down on the brake pedal .. you will have to pull the brake light fuse or battery will drain down.. the reason for that procedure is because no fluid will leak out of the master cylinder with brake pedal set down a bit...

I would have the master bled , again , just the master , see if it gets the pedal higher and harder.

I just did a brake line job on these and that brake pedal trick worked great .. brake fluid stayed in the master ...the air can though get into the master since the master is at the top .. so that is why I think that is the problem , try it..

O.K. update
Had a friend come over and
as she pumped the brakes slowly
air bubbles ( I'm told its called hydraulic pressure not bubbles) came up on the front small brake reservoir
none no bubbles (hydraulic pressure) in back big reservoir
called the so called mechanic he said
that when he bench bleed the master cylinder no air bubbles in the back big one at all
only in the front small one was there air bubbles (hydraulic pressure) when he was bench bleeding it
could it be a defective master cylinder ?
No way to be spending my vacation at home - Please help

perhaps he the mechanic , is an IDIOT or CROOK... when you pump the brake pedal down and hold it when bleeding , you then open the bleed screw and it should be solid fluid. this is solid pure hydraulic pressure. if any air bubbles that is a defect and the air must be removed resulting in the the soft pedal... because brake fluid/hydraulic fluids do not compress ,,,,,,,,,,,,, air does compress .. also air in brake fluid causes the fluid to breakdown because air has water ... the master does not cause a soft pedal ..he is trying to get more $$$ out of you , go to another shop have them bleed the system ... do not tell them any prior work done just tell them to bleed it. see what happens . if it fixes it which I believe it will. then I would tell all to not go to that mechanic .. a woman that requires vehicle repairs often [even dealerships do it ] are abused and ripped off.

I did call a couple other mechanics in the area
a couple seem to think maybe it's the
Brake Booster Check Valve
going to buy 1 tomorrow and new hose and clamps
then if that's not it spend $65 and get the brakes checked by a good shop
Thanks for your help j cat

I did call a couple other mechanics in the area
a couple seem to think maybe it's the
Brake Booster Check Valve
going to buy 1 tomorrow and new hose and clamps
then if that's not it spend $65 and get the brakes checked by a good shop
Thanks for your help j cat

sorry to hear you have not good vehicle servicing in your area. the brake booster or the vacuum check valve for it causes a hard high pedal not a spongy pedal. the master cylinder if bad causes the pedal to drop to the floor no braking. reason is it no longer can create pressure so the pedal drops down ALL THE WAY .. you have air in the brake fluid .. ask friends where to take it .just needs bleeding..

First, Sorry for the long response here
Thank You j cat
Went to the auto parts store, luckily got a man who I explained what was going on
Said it sounds like he did not
do the brake shoes and pads right to start, which started this mess
said even though he clamped it so he would not have to bleed the brakes, air got in the lines
Then said I needed new cylinders and calipers got them
He put them on, bled the brakes a couple of times,
then said my master cylinder had to have gone bad, so purchased that
man at the parts store said and then he didn't bench bled the master cylinder right, as I was there and no bubbles came out of the big side when he was doing it on small side had bubbles, then he put it on bled the brakes still no good brake
So called him, he said he will be over in the morning take the master cylinder off and rebleed it and bled the brake lines
asked him why he doesn't use the bottle method which seems the way I see most people say to do on bleeding the brake lines on you tube, said he never had a problem like this and will look into it over night
Mechanic Seems like he is ok just having a bad time which we all have, the parts store knows him and they always send business his way and costumers always say he's good and thank the employees for recommending him

well the soft pedal is most all the time air in the fluid and it don't take much. when bleeding brakes you use a clear plastic tubing and you place one end in a container with fluid in it and the other end on the bleed screw. if not then the air can go back in as the pressure drops. this is how DIY people do this . a repair shop will put a pressure cap on the master and force the air out . this is used because it is much faster and time is money.. this is why I suggested you go to a shop that can bleed the system properly .. appears to me too many parts replaced but perhaps they did require replacing .. having another shop look at his work should show what he did wrong .. post back how it was fixed.

the reason the auto part store recommends him is because ,he buys the parts at that store... LOL..

Harrah, fixed bled the brakes a lot of air in the lines
Thanks for your help j cat
Thought about the reason the auto parts store recommends him he seems
like he is honest enough and no charge today and gave me $50 bucks back
not many would do that
but next time I'm just going to a shop and getting it done

Harrah, fixed bled the brakes a lot of air in the lines
Thanks for your help j cat
Thought about the reason the auto parts store recommends him he seems
like he is honest enough and no charge today and gave me $50 bucks back
not many would do that
but next time I'm just going to a shop and getting it done

good to hear they got the air out. many forum members do not work on their vehicles but ask questions like you with auto tech's B/S stories.. It happens they replace too many parts so as to increase the profit. the soft brake pedal will be air most all the time. I am however surprised that I being 1500 miles away knew it was air issue , but not the guy working your vehicle LOL.. good luck ..