I recently bought an 01 Cherokee Sport (4.0l, auto, 2wd, 82k miles). I've actually only put 120 miles on it since I bought it. In that time I've replaced the electric fan and flushed the cooling system.

I got in this morning, expecting no problems, and my brake pedal was rock hard. It took a lot of force to get it to the floor, and even when I did, it did a **** poor job at stopping the beast.

The pads had been squealing, and the rear brake line sags quite a bit below the axle, both of these items are on the repair list...any ideas about the new problem? I'm thinking Vacuum Brake Booster?

If so, I'm seeing them from $71 - $100ish everywhere...Quadratec has a "Power Brake Booster" for $159...whats that all about?

 

Check and make sure the check valve is good before you replace the booster, better yet, make sure the hose is attached to it still. The check valve should only flow air one way blow either blowing or sucking on it, if it goes both, niether, or is extremely hard to force air through it is bad, other than that, sounds like you have a bad booster.

 

a check valve would be a great problem to have considering the alternatives. I'll look at that when I get home.

Anything else I should try before I get a new booster? I searched the site (with no luck) happen to know if there's a write up on replacing the booster here? I read elsewhere on the webz that you don't have to remove the master cylinder?

 

Yes you take the two nuts off and just move it forward, then undo your pushrod from under the dash and should be 4 bolts under there

 

How spendy are them valves? and are they a dealer only item. Thanks!

 

http://www.autopartswarehouse.com/de...e&apwidbmzuIrx

$22

 

So I took a look this afternoon, and I'm feeling like it's not the brake booster. Like I said, I'm no mechanic, and I've only had this thing for 120 miles....here's what i found.


The uppermost cable in this picture (with the flash glare) seems to be some sort of vacuum hose, it is deteriorated and was not connected.


I'm fairly certain the big black hole on the booster is where the check valve should be, yes? That's how it sits now, and when running there is a lot of suction at that round hole.

Now that I have a better description, can you point me in the right direction? I'm hoping its just a new hose, and a check valve?

 

Looking at your picture, it looks to me like your one way vave (check valve) on your booster is broken! The end cap is missing. Is there where you are feeling the sucking/vacuum? That is no bueno!

After replacing the check valve, an easy test to see if your booster is leaking.....the booster is made of two halves, crimped together around the outside of the housing. There is an oring that seals the unit up at this seam. Any air leaking around the o-ring...hard pedal. You can take a can of carb spray or brake spray (after fixing your massive leak at the check valve) and spray it around the seam/crimp with the engine running. If there is a leak, you will notice a slight stumble in the engines idle. You can use this same trick on vacuum hoses if you suspect a leak somewhere.

 

Awesome! This is a much better diagnosis, I'll replace that check valve and hopefully we can wrap this thread up. If that doesn't do it I'll update.

Thanks for the help guys!

 

$6 universal brake booster check valve, and the problem is solved.

You guys rock, thanks for all the help!