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manual brakes/ 99-04 WJ booster upgrade


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So my brake booster is dying... http://www.comancheclub.com/forums/viewtopic.php?f=2&t=32834

 

I'm wondering what my options are. There is the obvious factory replacement, the bigger booster upgrade from a liberty or WJ or something like that, or possibly manual brakes. I don't really want to go with the bigger booster since it is bigger and heavier... My mind is already set on not going that route. So I'm wondering about manual brakes. My dad has an 83 CJ-5 with factory brakes and 33" tires and the brakes don't seem all that bad and the fluid hasn't been bled in around 10 years either. I'm only running 31" tires and I'm figuring that I could get an aftermarket system from somewhere that would work better than his factory setup from 83 if I were to go that route. How do you guys feel about this idea? Has any one already tried this?

 

I'm thinking about the manual brakes for a couple reasons, First off there would be no booster taking up room under the hood, second there would be less weight, and third the brakes would work weather the engine is running or not. I have been is a couple situations were I was off road going up a steep hill and I managed to kill the engine. Right before It died, I mashed the clutch to try and save it which didn't work... So of course I'm rolling down a steep hill backwards while pushing the brake petal with all the strength I have and not even coming close to stopping. I should have let go of the clutch since it was already in gear but as I'm panicking, releasing the clutch is the last thing I'm going to think of. See why I would want my brakes to work with the engine off?

 

Sorry for such a long post..

 

Thanks for any input :wrench:

Chad

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You can go to a smaller bore like one used for disc brake early Mustang conversions to ease the pedal pressure needed a bit. 1" was common with drums, but SUCKS with big offroad tires. Going too small makes easy pedal, but the pedal goes down a LONG ways. Doing an XJ (from '97ish) on mine, but I'd sooner do a hydroboost (like manual brakes when the motor stalls. On a dime with 38" tires on my FSJ when running)

 

Another thought is newer XJ or ZJ brakes with a bigger bore caliper and wheel cylinders.

 

I replaced my rear wheel cylinders with ones for an Eagle (already had them for an Eagle I ended up scrapping due to rust) because they were bigger bore and I took the load sensor out, but I could lock them up (33") and skid in panic stops after that.

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Seriously? Vacuum power brakes are one of the most simple yet effective technological innovations. There's no good reason to scrap this system, unless you are doing an engine swap and there's no physical room for it. Weight is a non-issue, for both the stock singe diaphragm and the dual unit.

 

I'm in the process of upgrading my braking system with the dual power booster and manual rear bias adjuster. If you're comfortable on working on the brake hydraulics, it's pretty straightforward. You'd need to bleed a new MC and bend/flare some new line. Otherwise, just replace the booster and unless your lines are already in danger of exploding you can do it leaving the MC hooked up. Shop around, they are not that expensive.

 

If you want to go manual to solve a specific problem (no room from engine swap, no vacuum from radical cam, etc), or even "just because", then OK and who am I to argue. But don't try to convince yourself and others there are any real-world benefits to dumping a power system for manual. If you already have trouble stopping when you stall the engine... hit the gym. You don't need a full time manual, it's not an "upgrade". Especially with bigger tires, you'll be a menace on the road. Brakes are not something to mess around with. You're placing your life and the lives of others at risk.

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Thanks for the info. I'm thinking I'm probably just going to replace with a factory booster, but I'm still open to other options. Keep the comments coming...

 

Seriously? Vacuum power brakes are one of the most simple yet effective technological innovations. There's no good reason to scrap this system, unless you are doing an engine swap and there's no physical room for it. Weight is a non-issue, for both the stock singe diaphragm and the dual unit.

I'm asking for a reason...

 

Thanks comanche.gif

Chad

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Thanks for the info. I'm thinking I'm probably just going to replace with a factory booster, but I'm still open to other options. Keep the comments coming...

 

Seriously? Vacuum power brakes are one of the most simple yet effective technological innovations. There's no good reason to scrap this system, unless you are doing an engine swap and there's no physical room for it. Weight is a non-issue, for both the stock singe diaphragm and the dual unit.

I'm asking for a reason...

 

Thanks comanche.gif

Chad

 

It's just a mechanically elegant system that essentially does something for nothing. Very simple in design, but very effective. It functions like a lever, or imagine you're trying to free a stuck bolt with your 12" long 3/8" drive wrench and you put a 6' cheater bar on the end. Simple, right, but it gets the job done much easier? Engine vacuum and heat are natural byproducts of a gasoline engine that are typically wasted, unless you can harness that energy for something. In a booster there are two sides that are sealed off by a large plate; the vacuum side is valved to let air out, and the pedal side is valved to let air in when you step on the brake, so that when you press the brake atmospheric pressure pushes against the plate giving your foot a boost (think of how you can pick up a bowling ball with a vacuum cleaner). This is how you can stop a speeding 3000 lb vehicle with nothing more than your big toe.

 

The booster itself weights practically nothing, a few pounds maybe. You'll save more weight by cleaning the change out from under the seats. Simple things first though, have you identified where the leak in the system is? There are only three places really, inside the booster the diaphragm that separates the chambers could have deteriorated, the housing itself could be rotted out (underneath usually) and have holes, or the hose and/or check valve could be rotted.

 

A properly functioning system will retain the vacuum for quite some time after the engine shuts off, enough for a few power assists at any rate. How quickly do you lose the vacuum? You should be able to stick your head under the hood and turn the engine off and be able to hear where it's coming from, if you can't otherwise hear it over the engine noise. Are you getting a good boost while it's running?

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Not wanting to change to a dual diaphragm because of added weight is ridiculous. I'm not trying to sound mean, but in the grand scheme of things, the little (if any) added weight problem is greatly outweighed by the increase in braking performance. If you need to change it, make it better while youre at it. My 2 cents.

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So I can hear a hissing noise when ever it's running, and for a couple seconds after I turn it off. I disconnected the vacuum hose from the booster and capped it off, no more hissing noise. So i'm pretty sure it's in the booster...

 

Now that I kinda understand how it works, thanks to Jeepcoma, I see no reason to get rid of the booster.

 

I'm all for upgrading things to make them better if I'm already replacing them, that's why I have a dana44 and an nv3550. But I'm still not sure about the bigger booster uprgade, gonna do some more research on that.

 

Thanks :wrench:

Chad

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So I'm thinking about doing the 99-04 WJ booster and master cylinder upgrade. I understand how the brake light switch and the spacer need to go and all that. But should I do anything to the proportioning valve or the rear height sensing thing? Last time I bled my brakes I tried to use the special technique to bleed the by pass line or what ever it's called. I opened one of the bleeder screws on one of the front calipers and tried to bleed the rear brakes, the front one shot fluid every were. From what I understand, the proportioning valve was supposed to cut off supply to the fronts so it wouldn't spray fluid every were. Does this mean there is something wrong with my proportioning valve? Should I get rid of the rear height sensing thing? I like the idea of it adjusting the brakes but it's also one more thing that could go wrong... If it's even working right now.

 

If I get a JY booster/master cylinder is there a way to test it before I put it in?

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If you can wait a bit for answers, I hope to have this upgrade done soon and an update on braking performance and more pictures. I've so far bought and installed all the parts I listed in the threads and am finishing up bending the lines. I tossed out the rear height sensing valve and replaced it with a manual adjustable proportioning valve, and upgraded the booster and MC to the dual diaphram unit.

 

viewtopic.php?f=2&t=32143

 

Few pics also here and more to come. viewtopic.php?p=324164#p324164

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I want to get this done ASAP. Couldn't I just use a Cherokee proportioning block and run one line to the rear axle and take off the Height sensing thing? Should I take off the height sensing thing or just leave it on?

 

Thanks

Chad

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