brake trouble

[slowjeep]

I'm having trouble with the brakes on my 97 XJ.

Since I've had it, the brakes have been kind of soft, but the last week they have gotten very soft to the point that at a stop, the pedal slowly goes all the way to the floor. What should I check for to eliminate possibilities.

 

[Devilfrog]

Start with the basics ....

Fluid level, rebleed and see where you're at.
While you are bleeding the brakes check the soft lines for any swelling or bulges.
Check all fittings for seepage.

 

[Ecomike]

Check the fluid level in the MC.

If you hear a hiss, air leak when pressing the brake peddle, the vacuum booster is shot.

 

[slowjeep]

don't really hear a hiss, but the pedal does sink very far

 

[JaVeLiN]

Sounds like time for a rebuilt master cylinder...

 

[slowjeep]

hope that's it and not the booster.

I'll have to do as Devilfrog said and put a little time in before throwing stuff at it

 

[Ecomike]

Sounds like time for a rebuilt master cylinder...

Hard enough nowdays to get a new part that is not "junk in the box", LOL, much less buying a rebuilt POS! New ones are dirt cheap. Get cast iron if you can, NOT aluminum!!!!

 

[slowjeep]

who carries the cast iron piece?

 

[Planetcat]

The booster install is not that bad. You can get a reburb one for a decent price. My bet would be the diaphragm in the booster is shot.

 

[slowjeep]

boster or master cylinder....... hmmmm

 

[Ecomike]

boster or master cylinder....... hmmmm

Turn the engine off, and pump the brake peddle. Then if you can still press it to the floor, it is not Bosster, it is the MC.

I do not know if anyone makes a cast iron one for 97, but call and ask Rock auto, or your local parts stores.

http://www.rockauto.com/catalog/x,carcode,1180370,parttype,1836

If you get aluminum, get a high quality US made one, NOT CHINA!!!!!

 

[slowjeep]

yes with engine off pedal still goes to the floor

 

[Ecomike]

yes with engine off pedal still goes to the floor

Then the master cylinder is bad, or air got into brake lines, or a slave cylinder leaked. Check under the jeep for brake fluid near the brake lines, and at each wheel. Add fluid to the MC if it is low, and retest. If it is a brake line leak, or slave cylinder at the wheel leaking it needs to be replaced first. Then the brakes need to be bleed, to verify if the MC is bad.

If the MC is still full of fluid, and no brake line or wheel cylinder leaks can be found, then it is definitely the master cylinder.

Google for some you tube brake repair videos, they are all over the internet now.

 

[slowjeep]

I'll check for leaks and fluid level. each time it seems more like the master cylinder.

 

[slowjeep]

does the master cylinder necessarily leak if it is bad or could it still look good and fail?

 

[westvirginia24976]

does the master cylinder necessarily leak if it is bad or could it still look good and fail?

It can bypass internally. Think of a syringe. If there is a small tear in the piston it will create pressure, but will leak down. Everything is contained in the syringe, so you wouldn't necessarily "see" the leak.

 

[slowjeep]

that's what I thought. I took a quick look under the hood and no leaks. still shooting towards the master cylinder

 

[slk88xj]

Take the brake lines off the master and instal plugs if the pedal still falls then its the master. But if there's no leak externally then its the master. Its the only component on your brakes that can bypass internally and not lose fluid.

 

[slowjeep]

finally replaced the master cylinder this weekend. the booster was full of oil, drained it out, and everything is working fine.........