so I get in my Jeep yesterday and I start it up. I step on the brake and it goes right to the floor. Pumping it doesn't change the pressure. I put more brake fluid in it and that didn't help. I'm guessing either the brake lines are shot and are leaking or the master cylinder is toast. When I press the brake i hear a "hissing" sound coming from the front brakes.

Curious if anyone else had this problem, How much would I expect to pay for a new master cylinder if this is the case? Also installing new lines?

 

If you're losing fluid, you first need to find where exactly. You haven't stated if you lost fluid or not. The rear brake lines are great candidates for this to happen up here in the northeast more so than the front. Don't immediately figure on worst case before you completely diagnose the issue.

Start simple. Look at all of the brake lines and see where you are leaking from. Replace the bad one and look at the remaining lines in the same area and I'd advise replacing any going bad as a proactive approach. If need be, refill the master and have someone pump the brakes slowly and watch for spewing fluid. If no leaks, then it is likely the master cylinder, but not until you have ruled out leaking brake lines.

Remember, KISS! (Keep it simple stupid)

 

Yes the fluid was low, so I assume that there is a leak, it shouldn't be low if there is no leak.

I'll give your method a try... sucks because it's stuck at someone's house right now with non-working brakes. Had to leave it there since it wasn't safe to drive with the brakes not working like they should.

Thanks for the help. I've changed brake lines on a BMW before, just not on a Jeep. I hope they are simple if they are the problem.

Btw Love your Jeep.... always wanted Red Classic!!!! Jealous

 

At least it didnt happen on the road, my master went out coming down a mountain. But find the leak and you find the problem

 

Also what brake fluid do you recommend for the Jeep??

Thanks.

 

brakes on the xj are SUUUUPER simple... single piston caliper, 2 mounting/slider bolts mount them the the knuckle, & 1 simple bleeder screw

if u see fluid all over the back of ur tires, clear indication of a leak... since u hear a hiss, could be the piston cylinders' inner seal in the caliper is toast

could be a ripped brake hose (rubber) or hard line has rusted & a hole has finally opened up

in any scenario, if air is present in the brake system, the system will be compromised... which will happen with any leak, & in which case u'd need to bleed the system... also needs to be done when changin brake lines & calipers

dot 3 brake fluid... good luck! keep us updated

 

oh, & as fellow new englander, couple tips: SOAK THE HELL OUT OF ANY & EVERY BOLT THAT YOU'RE GONNA WRENCH ON WITH PB BLASTER/LIQUID WRENCH BEFORE YOU EVEN GET THE JACK OUT TO LIFT HER UP!! OR BETTER YET, DAYS IN ADVANCE

2nd tip: ANTI-SEIZE ON ANY THREAD, WHEN RE-INSTALLING

 

Make sure that whatever you do, you replace items in pairs.

If your driver's side caliper is leaking, and you put on a new one, the passenger side might then fail because it was weak, and the added pressure in the system from repairing the previous leak will cause it to fail. Replace both if you're going to replace one.. trust me, you don't want that head ache.

If you have the money, I'd just go and replace the master cylinder, rear wheel cylinders, and front calipers. Peace of mind.

I don't know about on a non-ABS Jeep, but on my non-ABS 77 Cutlass the Master Cylinder was $15. Completely worth replacing if you're already having a brake issue.