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No Power Brakes

L

live24wheel

NAXJA Forum User
Location
Phoenix
Hey folks, I am not having the best luck with Jeeps over the last couple weeks. Today my Jeep decided to lose its power brakes. I went out start it, it backfired through the intake and ran rough. I shut it down, started it back up and its running fine but I now have manual brakes. I checked vacuum lines and they all seem connected. Any idea? Its a 2000, 4.0, auto, 231. Thanks, Tom
 
i havent had any problems or hissing at all. i cant even hear anyhing noticable right now. It litteraly happene right when it back fired.... im wondering if it blew pressure the wrong way into that booster and blew it...
 
a large enough leak in the booster diaphram can cause a high idle, stalling and backfiring

it's possible the booster check valve blew out, its a cheap enough fix.

if you unbolt the master cylinder from the booster and pull it forward, you may find brake fluid has leaked inside the booster, from worn seals in the master.

This type of fluid leak is usually what ruins the the rubber diaphragm. The backfire was likely the result of a vacuum leak, not the cause.

if you pull the master off, and find no leakage, and there's no hissing in the cabin, the booster diaphragm may have ruptured. That would be a fairly rare one, more likely the check valve blew out.
 
Last edited:
yeah there is no vacuum leak or hissing inside the cab. Can you tell me if there is a way to test the booster, more about the check valve, and is there an upgraded booster available for the 2000? Thanks for all the help.
 
simple test- hard pedal, high effort to push with engine running=bad booster or leaky check valve

you need a vacuum pump and a set of adapters to test the booster, check valve and booster hose individually.

The check valve is pressure into the booster with a rubber grommet, and is connected to the intake manifold with a vacuum hose. It's a few bucks, and easy to change out.

there are no upgrades to a 2000 model year booster, aside from switching to a whole other braking system, like hydroboost
 
Last edited:
OK, got it fixed. It was the check valve. It blew the cap completely off of it. It also had a crack all the way down the side of it. I got a new one for a whopping 5 bucks and swapped it in. The difference from before to now is night and day. I can actually lock up my 33's with not a whole lot of effort!

Thanks for all the help. I didn't even know that was an item you could replace. Figured it was one of those buy a new check valve for $120 and get a free brake booster with it.

Tom
 
Blaine B. said:
It's better now than what it was before the rupture? Interesting.
Click to expand...

I didn't rupture... It was the check valve. That little plastic piece that the vacuum line attaches to that is hooked to the front of the booster. The old one was cracked all the way down the side so i'm guessing the booster wasn't getting the full vacuum it needed due to a leak right there.
 
Hey
I have an 88 with out abs.
I am going to put in all new master and booster
What kind should I get?
My brakes sick big time!
Like us there a better year to get it from?
 
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