Brake pedal to the floor

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Rottiedawg

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Any help appreciated.

'94 Wrangler YJ IL6 - Recently completed a full brake system replacement/upgrade (Calipers, discs, drums, pads, shoes, rear cylinders, master cylinder, power booster, etc.) Only thing not done were the lines. All this because brakes were mushy, worn and just lack luster with a pedal that went to the floor.

After replacing all including brake pedal still goes all the way to the floor. Only stops by standing on it. Replaced the master cylinder again thinking it was bad. Same thing (Yes, all has been bled properly and there are no leaks).

I'm starting to think its a vacuum issue to the booster. Not sure if it is relevant, but I also have a cracked exhaust manifold that will get replaced next month.

So, if it is a vacuum issue what should the pressure amount be at the booster? Someone suggested to me to replace all of the check valves. How many are there and where are they at?

Any other thoughts?

Thanks in advance...
 
Evening...you mentioned that it was all bled properly, does that include bench bleeding the master cylinder?
 
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The cracked exhaust manifold should not have an affect on your brake system btw...
 
If you have a vacuum pump, hook it to the check valve mounted to the brake booster and apply 15-20 inches of vacuum...vacuum should hold steady but if vacuum loss is indicated the check valve needs replaced...before all of that, I’d check for fluid loss at the master cylinder and leaks at all four corners including plumbing...
 
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I changed out both the hard brake lines and rubber brake hoses and it made a huge difference in my 92 YJ. The typical problem I had was the rubber hose had collapsed so the front brake didn't fully release and would drag, pulling the Jeep to the right and getting very hot. Two hoses in front and I think one in the rear by the differential.

Helpful hint.. I tried for hours to separate the hoses from the hard line and eventually resorted to cutting all the lines since I was replacing them anyhow. I bought a 20ft roll of Poly Armour hard line and shaped them to fit. It will require you to cut and make a double flair end, the auto parts store should have free loaner tool for doing the job.

Changing out the lines/hoses gave the brakes a firm positive feel.

I also had a frozen brake booster check valve, plastic fitting that connects to the hose and pushes into the brake booster. I was getting no boost prior to that. To test that part of the system just press on the brake pedal with the engine off and start the engine. You should feel the the pedal go further down when the engine starts.
 
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Chief Hof said:
Evening...you mentioned that it was all bled properly, does that include bench bleeding the master cylinder?
Click to expand...


Yes. Both MC's were bench bled. I also took it to a shop to check it. They are the ones that suggested an engine vacuum leak. Otherwise their next suggestion is that I got a bad Power Booster and need replace it.
 
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