I have a 1999 Jeep Wrangler 2.5 with 201,000 miles. I found that the front calipers were sticking, so I replaced both from calipers, disc and brakes. After doing so I bled the brakes starting RR, RL, FR then FL. Petel was firm but when I cranked the truck the brake light came on and the petel goes to the floor (toped off brake res and pumped the brakes to check for leaks.. nothing level stayed). I tried doing the process again (no air solid stream on all four) I even bled the master cyclinder to see if it was bad (plenty of pressure and no air detected). Do you know what could be causing firm petel with the engine on but sinks to the floor with ease when the truck is on?
Do you have ABS?
@chucktobias No sir, no ABS.
What method did you use to bleed the brakes? Are the new calipers installed with the bleeders at the top? Have you checked rubber brake hoses to see if any are ballooning under pressure?
@chucktobias I had a partner in the vehicle pump the brakes 5 times and on the 5th time hold the pedal while I cracked the bleeder once the fluid squirted out I would tighten it back and have him pump it again I did this about 4-5 times on each side the first go around to get all the air out the 2nd time it didnt have any air so I only did it 3 times per. The new calipers do have the bleeder on top just like stock. The rubber hoses seem fine, I did install a new bolt and copper gaskets.