Brake Question!!!!

[gmc 4X4]

Hey guys,

 

I am new to this forum.. I just bought a used 1995 gmc sierra 1500 4X4. When i bought the truck the seller said it needs rear brakes. The brake pedal was pretty low so i thought well maybe they just needed to be adjusted. The brake light was on and also the ABS light. Well i tore it all apart when i got home the rear brakes were fine, adjusted them and still a low brake pedal. So i bled all the brakes with engine off and pedal felt really good till you started the truck up then went almost down to the floor. I replaced the master cylinder and bled all 4 brakes again and still the same prob. But now my brake light and ABS light went out.

My question is what else could i do to get the brake pedal where is should be?? I was thinking booster or proportioning valve. There are no brake fluid leaks at all.

 

So if you guys could lead me in the right direction i would appreciate it.

 

thanks guys.

Phil

[GM-Tech]

I'm sorry to say that in the older trucks, a somewhat low and spongy feel to the brake pedal was normal. You can try everything in the world, but you'll never get a high, firm pedal on one of those.

[GM GIMP]

I'm certainly not a brake expert but I did have a similar poroblem on my 94 S10 Blazer. The front brakes were roasted but the rears were like new. This ended up being the ABS unit. (also had spongy and low pedal). After replacing the ABS unit I still had problems getting the system bled. My local dealership said they would need to cycle the abs unit using their equipment to get the air out. I then consulted a mechanic friend who said that anytime the system gives trouble bleeding he takes the vehicle out to a bumpy or gravel road away from traffic and slams the brakes from a speed somewhere just over 15mph and the ABS will then cycle. Usually the pedal will feel much better afterwards. I tried it and it worked after about three tries. No more problems.

 

If you decide to do this please be very careful. My recomendation is to take it to the dealer and let them fix it. I'm certainly not recommending what I tried since it can be quite dangerous. I'm just saying it worked for me.

[gmc 4X4]

ok guys, thanks for the advice..  I will try the what you said first about slamming the brakes.  And if that fails then i have no resort but to take it too the dealer. 

thanks

 

 

 

I'm certainly not a brake expert but I did have a similar poroblem on my 94 S10 Blazer. The front brakes were roasted but the rears were like new. This ended up being the ABS unit. (also had spongy and low pedal). After replacing the ABS unit I still had problems getting the system bled. My local dealership said they would need to cycle the abs unit using their equipment to get the air out. I then consulted a mechanic friend who said that anytime the system gives trouble bleeding he takes the vehicle out to a bumpy or gravel road away from traffic and slams the brakes from a speed somewhere just over 15mph and the ABS will then cycle. Usually the pedal will feel much better afterwards. I tried it and it worked after about three tries. No more problems.

 

If you decide to do this please be very careful. My recomendation is to take it to the dealer and let them fix it. I'm certainly not recommending what I tried since it can be quite dangerous. I'm just saying it worked for me.

 

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