Brake problem

[purple xj]

At a random time the brake pedal will go to the floor but once i pump it it goes back to normal it did it last nite but came back it just did it a second time tonite but rebuilt pressure out of no were fluid is good no leaks that i can see im really stumped could it be a MC i really need to figure this out its a DD

[Bandit1]

only time I had a loss of pressure was because I had a bad seal on a rear brake cylinder and was loosing fluid there. Looking at the rest of the lines and fittings, nothing was leaking. Check your calipers and cylinders for signs of leaking, then check your booser for proper pressure, then make sure you bleed all four corners to make sure you dont have air in the lines, after that, I dont know.

[Goonies.nsd]

Heat can cause issues. Swells up the pistons and rubber lines. Could also be the master with some of the same issues of swelling. Start simple and check all the caliper slides. Make sure there not sticking. Also check that the lines are not near a heat source. I know you just did the rear disc swap. So go over all of that.

Not to harp about it being heat. But if the fluid gets to hot it can pretty much boil in the lines and cause brake fade. Once it cools you get the normal peddle back. I had that problem with my ElCamino. The line to the rear was to close to my new headers. Harder i ran that car the brakes would fade. Rerouted the line on the frame rail away from the header and all was well.

Even with 4 wheel discs your still pushing those breaks with 35s. Alot of stopping daily with 35s and the caliper heat up to the point they cause hell.

[purple xj]

I was just cruising down highway went to hit the brakes no pressure let off the pedal repressed perfect pressure second time in 2 ninights i really need help with this the fluid was cold and cant find a leak

[Goonies.nsd]

MMM Sounds like theres air in the lines. Re bleed the whole system. Sounds strange that it acting up now so there may still be a leak. Even if you cant see a leak it may be very small. If it pulled in just a little air it can cause the problem your having.

[purple xj]

THe weird thing is though it will re build presure instantly ill rebleed the whole system tomorrow and see what happens

[purple xj]

So far the driver side front caliper is leaking fluid from the banjo bolt im getting a new caliper for free with new washers hopefully it fixes it

[HuLuD44]

When you did the rear disc upgrade did you take the bearing out of the master cylinder to equalize pressure to the rear brakes?