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WJ booster upgrade in the works. Couple questions


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My flare kit came in today and I've been messing with it. What did I get on the first try? A PERFECT flare. Those autozone rentals just can't be trusted!!!

why am I not surprised that you got a perfect one the first time?

 

Thanks for driving that point home. 

Those tools have been rented by guys that could mess up an anvil with a rubber mallet. 

 

 

You forgot the guys who could bend a digging bar in a sand pile.

 

Same sub species.......

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Did you get the lines with the booster/master? They're flexible.....

I did. Still had a little trouble getting the hard sections bent to where they wouldn't make tightening with a wrench a big pain. I'm sure there was an easier way to route them, but all that matters is it is done :D
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So I worked my tail off and bled the living crap out of the brakes just to crank it up and hear a SUPER loud hissing noise coming from the brake pedal and the pedal had NO resistance on it. I'm guessing that means the brake booster is blown? I guess that's what I get for buying a used one...

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Try the booster checks HERE.

thanks! With the jeep off the pedal is very firm and tight and doesn't drop at all. As soon as the Jeep starts the loud hissing begins and the pedal goes ALL the way to the floor. It slowly raises back up when I let off the brake but still goes right back down when pressed. Shut off the Jeep and the pedal goes back to being firm and nice...
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IMHO those symptoms point to the seals in the master cylinder being shot and bypassing when the additional 'oompf' of the booster is applied.

 

If you REALLY stand on the pedal with the engine off/vacuum bled, will it drop?

I pushed as hard as I could with both feet. Lifting me off my butt I was bracing my back against the seat so hard. And it went further down but was not soft in any way and never went more than halfway down. I stood on it for 30 seconds and it never dropped any more. Plus there is NO fluid drop in the MC. The constant snake hissing noise is what had me thinking its the booster.
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At least you can swap the booster without bleeding it... Rockauto has a reman for under $100US. Or a new one for not much more.

with speedperks 5$ off coupon and the 40$ off 100$ coupon I can get one tomorrow for about 160$ after taxes (I'll get back 65$ for the core). I just hate that I have to redrill and regrind the booster end. So do ya'll agree that it is most likely the booster being shot?
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Did you try sucking and blowing through the check valve?

I have the one from my MJ on it because it looked to be in better condition. I just went and checked both valves. The MJ one (which I have on it) is good. Lets vacuum suck through the valve but doesn't let air blow through. And the seal around the valve is tight. It takes a lot to push it in.
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AFAIK booster check valves are sort of universal, but I'm not positive. I'd still try a new booster check valve before springing for a new booster. O'Reilly's sells a (ugh) Dorman one (p/n 80189) that will work for about $6. Worth a shot.........

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AFAIK booster check valves are sort of universal, but I'm not positive. I'd still try a new booster check valve before springing for a new booster. O'Reilly's sells a (ugh) Dorman one (p/n 80189) that will work for about $6. Worth a shot.........

I'll give it a shot and then change the booster if it doesnt work out. Looking at the booster rod that connects to the pedal it looks like the seal is blown out. I'm thinking it just can't hold vacuum.
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Obviously something is wrong with the booster due to the sound it's making. The soft pedal just has stumped because everywhere is saying a bad booster causes a hard pedal. I can't see there being air in the lines because I literally ran a whole bottle through the MC before connecting the lines to the distribution block and then ran 2 bottles through the entire system doing the bleed all 4, crack a front fitting, bleed the rear, close fitting, bleed all 4. The whole system has 100% clean fluid.

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New booster is in. There is still an ever so slight hissing noise that increases with the rpms but the pedal is MUCH better than it was last night. The pedal is still spongey, though. So I will have to bleed more. But I believe once I get the bleeding done everything will be good.

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I just bled the brakes again. This time with my brothers pressing the pedal and me opening and closing the valve. I did 30 presses per valve, then cracked a front one and did 30 per rear valve, then closed the front one and did another 30 per valve. I just can't determine if this is how the pedal is supposed to feel... if I press hard enough it will go all the way to the floor. But the brakes lock up at about halfway down. I need to test them on asphalt but they locked up enough to slide 20 feet in my yard. I've just never had brakes that feel like this.

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