#1  
Old 07-30-2017, 05:22 PM
heckinohio heckinohio is offline
Senior Chief
 
Join Date: Jan 2006
Location: southeastern Ohio
Posts: 324
Default '97 GMC brake pain.......

Had this '97 for 200,000 miles. First of this month I noticed the brake pedal fading a bit when stopped at a traffic light. Braking efficiency was down noticeably . Got worse over the past week. This is the same exact symptoms I recall from old cars non power brakes when the master cyl goes away.......

Soooooo......I noticed the stamped steel painted bracket that shares the same mounting studs as the master cyl. was stripped of its paint & slightly rusty, typical sign of seeping brake fluid. I got a new master cyl today. Went through the bench bleeding. Followed all the instructions...... Now, I get the same thing, only the pedal resistance is elevated............when the pedal is first applied, the stopping starts immediately, then continued pressure on the pedal causes it to slowly move toward the floor several inches before stopping. about 2" from the floor.

What do I look for now.??????

PJH

  #2  
Old 07-30-2017, 05:46 PM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Catawba Ohio
Posts: 7,194
Default

Pin hole in a brake line is what I found with my 93 K3500 and I did the same thing you did, I replaced the master cylinder, same symptoms. No improvement and I found a brake line hole just under the master cylinder with a tiny pin hole in it.

If you haven't yet replaced all the brake lines on yours yet, your probably due. Mine started with rear lines and I just gave up and replaced them all along with both wheel cylinders.I used the Nicopp tubing (Nickle Copper alloy), bought a good quality double flaring tool (my old flaring tool was just flat out worn out) and made all the lines myself. The former owner repaired the rear lines with new prefabbed lengths of steel line just before I bought it, and they rusted out within 4 years.

The Nicopp will never corrode or rust and is easy to flare as well as bend. It's a bit pricey, cost me about $75 for enough tubing to do the whole truck, 25 ft of 3/16 inch, and 25 ft of 1/4 inch. With 100% new hard lines, flex hoses, and rear wheel cylinders, and I rebuilt both calipers. I should be good to go for as long as the truck runs, 260,000 on mine right now.

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1973 T/A (SOLD)
2005 GTO
1984 Grand Prix

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  #3  
Old 08-07-2017, 07:08 AM
ELKHORNAOG7 ELKHORNAOG7 is offline
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Join Date: Sep 2002
Location: DRUMORE,PENNA.( LANCASTER COUNTY )
Posts: 956
Question

Brake lines are good for about 100-150 th. miles before they need to be replaced going on 300 th. on my dodge diesel and had to replace twice, this time I used the copper/nickle line and it is very easy to work with-----BOB

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