Spongy Brakes

[demesauce]

I have been working on this for a while. My power brakes are really spongy, like pedal can touch the floor it I slam on the brakes. The bronco stops but it take a bit longer than I'd like. So far I have bled the brakes 3 times with slight improvement. I don't have a vacuum tester, but I don't think it is the booster. Any suggestions? Also the vacuum line that goes into the booster is plumbed into the intake manifold, not the carb. Does that make a difference?

Thank you in advance

 

[broncnaz]

What type of brakes do you have Disc/drum? A few things could be causing your issue. bad MC seals that are by passing fluid. worn out brake hoses that swell with brake pressure. or just leaky wheel cylinders.
booster vacuum line to the intake is fine. thats where its usually located no real differeance between there and the carb.

 

[demesauce]

I have disc up front and drum in the rear.

 

[broncnaz]

Most likely its the master cylinder. Is this a recent issue or has it always been a issue?

 

[demesauce]

It's been that way ever since I owed it. And the PO said the brakes were pretty spongy when I first bought it. No recent changes

 

[broncnaz]

What disc conversion does it have? Some people have needed a MC with a larger bore size Might want to check to see what size the bore in your current MC is. A small bore size may cause excessive pedal travel you may need to go up to the next size MC to get more fluid volume.

 

[DirtDonk]

Another common issue is the clearance between the back of the master's piston and the tip of the booster's rod.
Easy enough to check quickly by removing the master (you don't need to disconnect any fluid lines usually), pull it away far enough to measure the depth of the piston recess, measure the extension of the adjustable rod inside the booster, and compare the two.
If it looks like you have more than just a hair of clearance, it will give you a soft pedal.

Of course, so will air in the system, and a few other things, but this is a common issue, along with what the others said.

Paul

 

[demesauce]

Since this isn't due to a recent change is there something I should check first? Like maybe change the master cylinder first?

 

[Justafordguy]

If it's aways been this way I bet the front calipers or on the wrong side. You can't get all the air out of them if they are. You just need to swap sides if that's the problem. If you look at the location of the bleeder very closely you will be able to tell.

 

[demesauce]

If it's aways been this way I bet the front calipers or on the wrong side. You can't get all the air out of them if they are. You just need to swap sides if that's the problem. If you look at the location of the bleeder very closely you will be able to tell.

I'll be able to tell what? I thought if the bleeder screw was pointing up, then it's on the right side. Are the calipers marker by a Left/right stamp?

 

[Skiddy]

I'll be able to tell what? I thought if the bleeder screw was pointing up, then it's on the right side. Are the calipers marker by a Left/right stamp?

no they are not stamped, yes the bleeders point up