98 Chevy Truck brake line bleeding.

Messages
178
Location
Pennsylvania
Wife came home the other night and said the brake light on the dash was on and that the emergency brake was released so it wasn't that. Gave her some credit for that! I checked the fluid level in the master cylinder and it was low. Crawled under it and saw a leak in the metal hydraulic line running back to the rear brakes. So I replaced a 6 foot section of the line without difficulty and had my daughter help me bleed the system after filling up the master cyl. with fluid. We pumped a lot of fluid out at the rear bleeders and got no air......all fluid. I guess my question is if we didn't get any air out back there after replacing 6 feet of line we didn't pump enough fluid out yet? Bad thing is I moved to the front calipers doing things in the proper order and both bleeders are corroded to nothing! I have reman. calipers coming from Rockauto so I can properly bleed entire system but expected to get air out at the rear since the line replaced feeds the back brakes? Any insight please? Thanks, Scott
 
Messages
4,437
Location
Guilford, CT
You shouldn't really need to bleed the fronts if you only opened a rear line. I just replaced a front brake line on the Explorer yesterday. I only bled that one front corner and that's it. I have a nice firm pedal.
 
Messages
25,814
Location
Upstate NY
Well I hope you used copper/nickel brake line. Or you will be doing it again. Your post does not mention how good or bad the brakes are now? Before I would replace the front calipers I would get some new bleeder screws, they spray PB Blaster, wait overnight and spray more, wait 5 minutes and try with vise-grip or a rounded bolt remover socket.
 
Messages
1,819
Location
ventura, ca
It might not be the same set up but on my 94 I had to have the key on so the ABS stuff was working or I didnt get much pressure to the rears. If you had good pressure when you bled it then that may not be the case for a 98.
 
Messages
36,461
Location
ME
If it was leaking it could have done a "gravity bleed" without you knowing it. Yeah it might have sucked in a pico liter of air when driving it before but the gravity popped it back out. It sounds like you got to it before the master cylinder ran dry, a good thing. If it feels solid you're GTG.
 
Messages
25,945
Location
MA, Mittelfranken.de
Put the rear up on ramps or stands and tap the caliper with a rubber mallet or dead blow hammer a few times then have someone push the pedal and loosen the bleeder.
 
Messages
1,697
Location
Auburn, GA
Agreed with others, it should be fine. Your '98 - is it an NBS (GMT800 - 2000's body style)?? Or the older GMT400 (90's body style)? If the GNT800 - the rusted brake lines is a SUPER common problem. Thousands of complaints to the NHTSA, and no recall. They do make a 'service kit' though that replaces the 5 main lines in the truck, pre-bent and coated with some black stuff that they probably should have been from the factory - (2) from the master to the BAS pump. Then (1) from the ABS pump to the rear axle, and (1) to each front wheel from the ABS pump. I'm in the middle of replacing all 5 lines right now in a customers '02 Avelanche.
 

wolfehunter

Thread starter
Messages
178
Location
Pennsylvania
It is the older body style (90's). I will try it with the ignition on and see if that makes a difference as the brakes feel a little spongy or soft. But I remember they always felt a little soft compared to the other cars we have. This is not a daily driver so it is hard to notice any difference. I "jumped" on the brakes on a dirt road near home and could only get the front tires to drag. Gonna try and bleed the rears again with ignition on and see if any difference. Next question: How do I get the brake light on the dash to go out?
 
Messages
8,598
Location
Florida
Originally Posted By: wolfehunter
It is the older body style (90's). I will try it with the ignition on and see if that makes a difference as the brakes feel a little spongy or soft. But I remember they always felt a little soft compared to the other cars we have. This is not a daily driver so it is hard to notice any difference. I "jumped" on the brakes on a dirt road near home and could only get the front tires to drag. Gonna try and bleed the rears again with ignition on and see if any difference. Next question: How do I get the brake light on the dash to go out?
If the system is full, I would suspect a fluid level sensor is no working correctly. It can happen when working on an old brake system that hasn't been opened in a long time.
 
Messages
1,697
Location
Auburn, GA
Those brakes never felt 'good' from the factory. GM designed a brilliant (on paper at least) variable pressure master cylinder that varied output pressure based on piston speed (how fast or slow you pushed the pedal). It's common for people to swap the 'NBS' master cylinders into these trucks for significantly better pedal feel. If there's no air in it - just drive it.
 
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Messages
5,651
Location
Iowa
Try adjusting the rear brakes up some- just until they start dragging. If they are too far away from the drum, the the pedal will have extra travel, feel soft or mushy and they often won't have the grab they should.
 

wolfehunter

Thread starter
Messages
178
Location
Pennsylvania
I ended up gravity bleeding the rear line and got air out of them. Light went out on the dash and feel of brake is back to normal. thanks for the suggestions!
 
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