1999 gmc jimmy brake probs

[OHEARN.2012]

ok so my buddy has a 1999 gmc jimmy its a 2wd has abs but the problems is there is little tp no brakes all the pads are good we went out to work on it today and all pads and calipers are good. we thought it was the master cylinder so we replaced it. we got that replaced and bled all four calipers we had good fluid to each. we never let the fluid run low but we still got nuin. his grandpa thinks it the abs and i read that when the abs computer is bad it will make the brakes crappy. we have vacuum at booster to. so if anyone could steer me in the right direction itd be awsome thanks

[old school truck dude]

Crappy in what way? Goes to the floor? Gotta push real hard just to slow down? Spongy pedal? Pulsating pedal?

[OHEARN.2012]

we got nuin then right before the floor we get some brake

[Bigdaddy]

check wheel bearings

[OHEARN.2012]

wheel bearings would cause bad breaks??

[Bigdaddy]

yup, if they are wore out in the front, brake pedel will go to the floor...

[old school truck dude]

we got nuin then right before the floor we get some brake

Adjust rear shoes, make sure shoes are centered in the drum by pushin pedal frequently while adjusting. Tighten until brakes drag on wheel just a bit. Pullin up on the emergency brake or backin up and steppin on the brakes to cause automatic adjusters to do the job doesnt always work very good..

[damn_ford]

we got nuin then right before the floor we get some brake

Adjust rear shoes, make sure shoes are centered in the drum by pushin pedal frequently while adjusting. Tighten until brakes drag on wheel just a bit. Pullin up on the emergency brake or backin up and steppin on the brakes to cause automatic adjusters to do the job doesnt always work very good..

99 jimmy should be 4 wheel disc.

clamp off each of the rubber hoses 1 at a time and see if the peddle comes back. that will lead you to the problem. if you didnt bench bleed the master before you put it on your gonna need another and follow the bb instructions to the letter.
sounds like you have air trapped in the system and just are not getting it out

take it up to frankenmuth muffler man. FREE inspections, you dont have to have them fix it but it sounds like your in over your head and need someone that knows what there doin to look at it.

[old school truck dude]

Ah, technology.. Didnt realize theyre rear disc..

[OHEARN.2012]

well his gpa knows alot of stuff about this...

the master cyclinder was off a truck at a junk yard so it was ready to go

[OHEARN.2012]

wat are you saying by clamping off lines are you getting at that the calipers are bad??

[old school truck dude]

wat are you saying by clamping off lines are you getting at that the calipers are bad??

No, that will show a leaking line or master cylinder. Youre eliminating the caliper from the system by clampin the hose to it. Process of elimination is how you figure out whats wrong with stuff.

[old school truck dude]

well his gpa knows alot of stuff about this...

the master cyclinder was off a truck at a junk yard so it was ready to go

Still needs bench-bled before installation

[old school truck dude]

wheel bearings would cause bad breaks??

Causes the pads to be pushed back out

[OHEARN.2012]

well how do we bench bleed a mastercyclinder??

[Blazin40s]

Remove master, and plug off hose holes and slowly push in rod about an inch till the bubbles stop.  That's the new way...old way u use hoses in holes

[damn_ford]

well how do we bench bleed a mastercyclinder??

buy a new one, it comes with directions. used mastercylinder is not the way to go

[chevyjake]

sometimes if you get air in the lines it can get trapped at the abs moduale, and the only way to get the air past it is a tech 2 scanner to actuate the module during bleeding.  i would start with bench bleeding the master then try and bleed the system doing RR,LR, RF then LF. after all that if there is still a crappy peddle id believe its air at the module and a brake shop could help you.

[old school truck dude]

If it has a proportioning valve it could be stuck, have somebody beat on it (not too hard ) while you push the pedal

[Disturban]

sometimes if you get air in the lines it can get trapped at the abs moduale, and the only way to get the air past it is a tech 2 scanner to actuate the module during bleeding.  i would start with bench bleeding the master then try and bleed the system doing RR,LR, RF then LF. after all that if there is still a crappy peddle id believe its air at the module and a brake shop could help you.

I second this opinion because it happened on my moms car, when the abs system gets air trapped in it you need the scanner to bleed it, it is kind of a pain, need to open each valve for each channel when you bleed the system, that truck is a 3 channel system, one for both back wheels and one for each front wheel.

Also agree with the master cylinder, need to bench bleed it even if you pulled it was used and full of fluid, personally I would buy a new one, I don't like used parts when it comes to my brakes especially when you can get a new one for about $100, how long has that used one been sitting in the bone yard full of moisture corroding the piston and cracking the seals?

If there was any moisture (Water) in it at all when it sat all winter and froze it will destroy the seals, you might have just replaced one bad part with another bad part!