istaywikkid Posted December 6, 2014 Share Posted December 6, 2014 What's up everyone? In the mix of trading my yj for another Comanche and I'm having the problem of the pedal going to the floor! It's a 89 Mj, replaced booster, master cylinder, all new lines, wheel cylinders and it has new pads and shoes When I press the pedal it hisses and drops all the way to the floor Bled the master cylinder and all the brakes, helped none :( Can anyone help me out? Link to comment Share on other sites More sharing options...
Dillithium Posted December 6, 2014 Share Posted December 6, 2014 Is the vacuum line attached to the booster? If there's a strong hiss and it drops to the floor, in my mind that sounds like a bad booster. Have you checked for fluid leaks? Link to comment Share on other sites More sharing options...
nitroxsteve Posted December 6, 2014 Share Posted December 6, 2014 What was it doing before you replaced all the parts? Link to comment Share on other sites More sharing options...
Truckcom Posted December 6, 2014 Share Posted December 6, 2014 Be sure the weld above the pedal has not sheared. Link to comment Share on other sites More sharing options...
istaywikkid Posted December 7, 2014 Author Share Posted December 7, 2014 No fluid leaks and the guy replaced the booster, might be defective (at least I'm hoping) and he said it would stop but every once in awhile he would have to pump them. And as for the weld where would I look at to see? I'm not at the truck right now I'll be back there in the morning Thanks for replies Link to comment Share on other sites More sharing options...
Pete M Posted December 7, 2014 Share Posted December 7, 2014 is the pedal firm with the truck off? Link to comment Share on other sites More sharing options...
91Pioneer Posted December 7, 2014 Share Posted December 7, 2014 There are a few tests you can do, my booster is broken but my pedal goes down the normal amount (I have a hard pedal). With the truck off, press the brake pedal a few times, then with your foot on the brake, start the engine and see if the pedal drops. Second, with the engine off after running it to build vacuum, disconnect the hose going to the brake booster, you should hear the vacuum. There are other things you can try, google brake booster diagnosis. It sounds to me like the booster is faulty but I'm not a mechanic. Link to comment Share on other sites More sharing options...
istaywikkid Posted December 7, 2014 Author Share Posted December 7, 2014 Well I was under it today. Would the little splitter valve for the brakes in the back be an issue if that was removed? He took it out and put a 3 way there.... Link to comment Share on other sites More sharing options...
91Pioneer Posted December 7, 2014 Share Posted December 7, 2014 Could be part of the problem but I doubt it's the root cause here. Is the fluid level OK? Did you bench bleed the master cylinder before installation? Link to comment Share on other sites More sharing options...
istaywikkid Posted December 7, 2014 Author Share Posted December 7, 2014 Yea and I bled the brakes after Link to comment Share on other sites More sharing options...
91Pioneer Posted December 7, 2014 Share Posted December 7, 2014 Did you bleed the rears properly (twice)? There are two rear lines and you need to simulate a front brake failure as part of the procedure and do a second bleed. The MJ brake procedure is not exactly like regular vehicles. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted December 7, 2014 Share Posted December 7, 2014 Did you replace front calipers? Link to comment Share on other sites More sharing options...
istaywikkid Posted December 7, 2014 Author Share Posted December 7, 2014 Won't hurt to try that and yes I did replace them Link to comment Share on other sites More sharing options...
Jeep Driver Posted December 7, 2014 Share Posted December 7, 2014 Well I was under it today. Would the little splitter valve for the brakes in the back be an issue if that was removed? He took it out and put a 3 way there.... The line back to the distribution block at the master needs to be eliminated. Remove the '3-way'. Link to comment Share on other sites More sharing options...
Jeep Driver Posted December 7, 2014 Share Posted December 7, 2014 If your prop valve has been eliminated, this is all you should see at the rear axle line- You have air in the return line and no way to bleed it out. Image Not Found Link to comment Share on other sites More sharing options...
Pete M Posted December 7, 2014 Share Posted December 7, 2014 I agree. except that it's not a return line, it's the emergency bypass line. :thumbsup: Link to comment Share on other sites More sharing options...
ScottJeep Posted December 7, 2014 Share Posted December 7, 2014 Make sure bleeder valve is at THE TOP on the front calipers. Yeah I know it seems silly... late, tired...beers...ask me how I know. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted December 8, 2014 Share Posted December 8, 2014 The same way I know...doh! It seems like the calipers should just have simple R and L stamped into them...the weird part is that they'll fit either way...but the result is endless bleeding and no pedal. Link to comment Share on other sites More sharing options...
Guest Posted December 8, 2014 Share Posted December 8, 2014 Finally get to use my ASE smarts for something. Yay Few tests you can do to diagnose this. IMO, there's air in the lines, that's why the pedal is "spongey" and falls to the floor. 1. Make sure the master cylinder has fluid in it (obviously) 2. When the truck is off, pump the brakes a few times to see if pressure builds up. Turn the truck on, and if the booster is working properly, then the pedal should fall slightly towards the floor. 3. If the booster seems in proper order, where the line running from the intake manifold to the booster is, gently pull the check valve towards the nose of the truck. This is a sure fire way to see if the booster works. If you hear air "whooshing" into the booster, then it's operating as normal. 4. Bleed the system again; starting with the passenger rear, driver rear, passenger front, driver front, in that order. There's also a special bleeding procedure for the bypass line, a quick search will pull up a thread on it. I don't remember it off the top of my head, or else I'd tell you how. 5. Once bled properly, you should have usuable brakes again. If this doesn't work, Then I'd suggest you re-examine the booster. If the booster fails, you'd still have usuable brakes, but you would not have "power assist". Like I stated previously, I believe your problem is that there's still air trapped in the lines at a high point somewhere in the system. I would start with number 4 before trying 1 through 5. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 8, 2014 Share Posted December 8, 2014 Well I was under it today. Would the little splitter valve for the brakes in the back be an issue if that was removed? He took it out and put a 3 way there.... If he did it wrong, yes. Link to comment Share on other sites More sharing options...
istaywikkid Posted December 9, 2014 Author Share Posted December 9, 2014 Well I put in a new booster and master cylinder yesterday. Bled everything perfect. I got enough brakes to bring the moody truck home. Just still takes some pressure to stop the tank. It's quite confusing because I'm looking at my 88 Mj and its all looks the same,and my 88 brakes perfect but the 89 just doesn't like to stop Link to comment Share on other sites More sharing options...
91Pioneer Posted December 9, 2014 Share Posted December 9, 2014 ...Bled everything perfect.../quote]Does that mean your blood them according to the proper Comanche-specific procedure? Link to comment Share on other sites More sharing options...
istaywikkid Posted December 9, 2014 Author Share Posted December 9, 2014 ...Bled everything perfect.../quote]Does that mean your blood them according to the proper Comanche-specific procedure? Yea bled the rear twice right? Link to comment Share on other sites More sharing options...
54bobby Posted December 9, 2014 Share Posted December 9, 2014 there is 2 different rear shoe sizes. have you got the correct ones? Link to comment Share on other sites More sharing options...
istaywikkid Posted December 9, 2014 Author Share Posted December 9, 2014 That I might have to check lol I didn't install the shoes so idk Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now