98 gmc jimmy 4.3 liter. brake pedal to floor after ok previous day. eventually stops me although don't stop on dime. hubby replaced lines from mc back (rubber and metal) part of line. Tried to bleed after replacing and it wont, none of them. I know he had fitting all way open to bleed. He has been extremely busy and I cant get him to explain any more on what needs to be checked now or what else could be. I just cant drive like this anymore. He said tues cant wit 2 days. anybody please???? Need help so I can possibly get said part for him. Hopefully not MC as I know its a pain in the ass to replace. Anybody had this issue or any suggestions?
With that much line replaced, it's going to take some effort to bleed. Somebody has to sit and pump the brake, while somebody else works each bleeder nipple starting at the furthest from the MC (probably right rear) to the nearest.
Another option is to slightly crack all nipples on all calipers (rear cylinders probably on a 98 Jimmy) and just let them drip. Can't let the MC reservoir go dry.
If the master cylinder went dry, the best bet is clean tubing from the left front nipple dumping back into the reservoir. Pump your heart out until there are no more bubbles. Then bleed as normal, all four wheels. Twice.
If you don't have a scan tool with ABS bleed capability, then take the vehicle to someplace safe and slippery (wet grass, slick road, mud) and do some extreme panic stops where you can feel the ABS engaging (pulsing in the brake pedal) a half dozen times. Then bleed all four again.
The last part is because I'm anal... honestly you just need a proper bleed and all will be well.
I have a 97 suburban, so the braking system should be very similar. I have replaced lines/hoses/calipers/wheel cylinders on this truck and spent hours of time and over a gallon of fluid trying to get it bled correctly. A couple things that I've learned and have helped.
If the master ran dry, be sure to bench bleed the master and ABS. Remove the lines, install short lines, and have them go back to the reservoir on the master. Pump until no bubbles. Reinstall the lines that go from the master to the ABS. Individually bleed the lines that come out of the ABS pump. I didn't try bleeding the ABS, but I think it would had helped as I am almost positive my issues were at the ABS pump.
A couple methods I've used:
Normal pump bleeding - Open the bleeder, push the pedal down, close the bleeder, release the pedal. This will help from air getting trapped. I never quite got it right with this method, but I was using the old hose in a bottle method and not closing the bleeders in between pumps. Leaving the bleeders open while pumping can allow air to get sucked in past the bleeder threads, or can allow a bubble to get pushed back and forth, but stay in the line.
Pressure bleeding - apply pressure to the master cylinder reservoir to push fluid through. Might had worked had the top been able to seal well, but it ended up just making a big mess.
Vacuum bleeding - apply vacuum at the bleeder. I've used a hand pump and a large vacuum pump. Be sure to use a ton of Teflon tape so you don't suck air from around the threads. If your hose doesn't fit tight around the bleeder, you will get tons of bubbles.
Reverse bleeding - Push fluid from the bleeder back through to the master. I build a tool to do this. A sauce jar with one line that I could connect to the air compressor, and one submerged line that would push fluid through. I used a regulator to limit the pressure to about 3 PSI. Again, use tons of Teflon tape as to not suck air around the threads.
I ended up modifying some bleeders by cutting the tip off so I could screw it all the way down to ensure no air would get past the threads. Used a ton of Teflon tape. Vacuum bleed until I purged the line, reverse bleed, install original bleeder with a ton of Teflon tape, vacuum bleed until I don't see bubbles. Keep a good eye on the reservoir, you don't not want to run it dry or you will have to start over.
I think the reverse bleeding helps get the bubbles out near the master/ABS where there is a long drop. The bubbles want to go up, and normal methods are trying to push them down. I might had had good success with bleeding the ABS first also.
You should also note, part of the official bleeding process is to have the dealer run an automated bleed on the ABS system. This takes a very specific scan tool. I tried several of my cousin's professional Snap-On scan tools, and they were not able to do the ABS bleed.
Another note on the ABS. If your standing at the drivers side fender looking at the ABS pump, near the back is a rubber cap. Remove this cap and underneath is a valve you can press in with an ice pick. I have somehow used this to bleed the ABS before. I believe I would press down the valve, have someone press the pedal, and release before they stopped pressing. Beware that this will spray fluid everywhere.