brake booster...what is it?

[uiuc240]

OK, so the brake booster. The large, round, black thing that your master cylinder hangs from. What is inside that?

I know that it takes vacuum from the motor and converts it into a useful boost in braking power...but how? What's in there? Are there any moving parts? Is there anything that can actually wear out? Is there anything rebuildable?

I'm asking because my pedal feel has slowly been getting "crunchier" ... if you can imagine that. I don't know if it's something caliper-related...but I'm trying to rule out other things first. The master cylinder is a reman, but only aobut 3 years old. The Z brakes are old (1990), but they were rebuilt when I put them on the car 3 years ago.

I know I need to pads and rotors, but I think the "crunchy" feel I'm getting is something else.

Any ideas? (Calling all brake gurus!)

Eric

[cdlong]

the brake booster does have moving parts but not many. inside the shell there is a diaphram seperating two seperat chambers. that diaphram is connected to the shaft that pushes on the MC. one chamber, towards the front of the car has a vaccum, the other has a vaccum until you step on the pedal. when you do that it opens a passage that allows atmospheric pressure into it. the pressure differential adds extra force to the MC shaft.

basically the only thing that can go wrong is the diaphram can leak and you will loose the extra power. i guess it could be rusted out inside but it's unlikely since it's high up under the hood and most cars pull air from inside the passenger compartment anyway. it's more likely that some of your calipers or rotors are bad. just jack the car up and check out everything. i assume you mean the pedal stroke is getting crunchier, not what the brakes feel like after they've been applied.

on a side note, what are the specs on your wheels?

[uiuc240]

Yes, the pedal travel is sorta crunchy. You think it really could be the calipers? I hope not, but I guess it could be that.

However, I *do* know that the rotors are badly scored...I will never get drilled rotors again. The back side is all fubared. Would that cause this strange feeling? It's been slowly getting worse and worse, and now it's quite annoying. Should I try pads and rotors first?

The wheels are cheap, old MB Motoring wheels...made by Prime for Discount Tire. They are 17x7 with approximately a +35 offset. They were painted by me last year. They simply hold the tires on the car...nothing special. I want better ones, but that costs money. :-)

Eric

[DuffMan]

Is the "cruchy" feeling the same at all speeds? Does it occur when stopped?

[uiuc240]

It's less noticeable when driving. It's more obvious when I'm slowly coming to a stop...or if I'm basically stopped and I ease onto the pedal just a tad more.

Thoughts?

[DuffMan]

The only thing that comes to mind is maybe air in the lines, causing an inconsistancy in braking response, or (and this is a long shot) one of your pads may be actually falling apart, and be cracked or have a rock or something embedded in them.

But I would start with bleeding them, because that is probably the cheapest thing you can do.

[pearlwhiteS14]

Eric if you need to look at it you can bring it over to my garage? It may be a little easier for you, if that will help?

[uiuc240]

Hmm...I might take you up on that :-)

I don't think it's air in the lines, though, as the pedal feel is still FIRM...it's just not smooth like it used to be. I think it would be good idea to take the pads out and inspect them, though. I mean, I was already planning to get new rotors and pads in the next couple of weeks. I'll be bleeding the system at that time as well. I was just trying to get an idea of whether or not I need to rebuild the calipers/master cylinder/brake booster at the same time.

So let me ask this...does the brake booster have any affect on pedal feel? Does it actually *touch* the lever arm or the piston? I *do* know that the outside of mine is a little rusty because when the master cylinder went bad 3 years ago, it dribbled brake fluid on the booster...that caused the exterior to rust. Could it be rusting on the inside because of that?

I'm just trying to figure out how many parts I should plan on buying/replacing.

Should I just replace my entire hydraulic system?

I could get a new clutch master and slave as well...and the rear SS lines and the clutch SS line. And a rebuild kit for the calipers, I suppose. Geez. That's going to be rough on my wallet. But I guess if it has to be done...

What do you guys think I should do?

Eric

[cdlong]

the booster does affect pedal feel, but it's hard to describe how, it's not the same as the MC. i would bet it's your rotors and pads since they are messed up. since you were going to replace those anyway i'd start with that and see if that fixes it. fluid gets on the outside of the booster occasionally, it's not a big deal if the outside rusts. it is possible that some got inside and messed up the internals though. can you feel the crunchiness when stopped or just when you are bringing the car to a stop with the brakes? like i said, just replace one thing at a time and see if that fixed the problem.

the clutch hydraulic system is seperate, no need to replace that if there isn't a problem.

got any better pics of your wheels? they look about as flush as i want, it makes me think that the 7.5 +17s that i want are going to be too low

[kandyflip445]

I don't see how it could be the booster though. If it were a faulty booster I can't see how it would give a Crunchy feel to the brakes. It would seem to me the different feel would be present all the time. Let me look in my big brake book and see if there is anything about "crunchy brakes" or something of the sort.

[uiuc240]

The crunchiness is minimal when just driving normally...I can only *really* feel it when the car is going less than about 5 mph. Then it becomes pretty obvious. What do you think this means?

I know the clutch system is separate...I was just thinking that if I was going to go hog wild, I might as well just get *all* new stuff and make it niiiiiiice.

I have other pics of my wheels, but they are on my photo album at EPSON.com and I can't get to it from my work account. See if you can search for it. My library is under uiuc240 there too. Sorry, that's the best I can do...can't remember the address for it. I'll say this though, 17x7.5 +17 is going to be sticking out past the fender.

Eric

[kandyflip445]

I think the pads and rotors would be your best bet right now. (Still haven't looked in my book yet) Just thinkin about it....have you ever stuck your hand up to a room fan that was on? When you put your hand there it keeps your hand kinda out cause it keeps hitting it but when the fan slows down you can feel it more cause your hand is able to move towards it more. Dunno if that makes any sense but it's what I was thinkin at the moment.

[cdlong]

Originally Posted by uiuc240

I have other pics of my wheels, but they are on my photo album at EPSON.com and I can't get to it from my work account. See if you can search for it. My library is under uiuc240 there too. Sorry, that's the best I can do...can't remember the address for it. I'll say this though, 17x7.5 +17 is going to be sticking out past the fender.

it's not working, i need your e-mail address. don't worry about it, no big deal.

[uiuc240]

email is [email protected] if that helps.

and the whole fan thing took me a bit, but I see what you mean. maybe i should just start with a pad/rotor/fluid swap and see how that goes.

any good links to sites for Brembo blanks?

suggestions on pads? should I bite the bullet and go with Porterfield?

Eric

[uiuc240]

Any thoughts on pads, dudes?

And where to get the rotors (any good deals you've seen)?

Eric

[cdlong]

nopi has good deals on brembo blanks. i have hawks HPS on my car and i love them, if i was into more serious racing (more than autoX) then i would probably get the HP+. with the Z brakes, either would be fine for anything short of extended hot laps on a track.

that epson site sucks by the way. oh well, it's not like i can afford any wheels right now anyway.

[Dream240]

Originally Posted by uiuc240

Any thoughts on pads, dudes?

And where to get the rotors (any good deals you've seen)?

Eric

Check out this site for Brembo rotors. Not bad, but I think eBay has better deals.

http://www.performancerotors.com/index.php

Here's a link to a sample of ebay goodies.

http://cgi.msn.ebay.com/ebaymotors/w...category=33564

I know you said you hate Cross-drilled, but why? Also for pads, I've got Hawk HPS on my 30mm front upgrade and they're sweet. No brake fade no squeaking, good bite, low dust. A little pricey but well worth it.

Just a thought but, stock front rotors suck pretty bad, why wouldn't you go with Cross-drilled/slotted again? Stock brakes for me warped waaaay to easily. My last upgrade was CD/slotted all the way around and for 2 years I beat the hell out of them, minimal warpage(0.2825mm). I had brembos and PBR pads with that setup. Still got them on the backs but working on the 300zx upgrade there too!!

You said the rotors were chewed up on the inside face? Did you use old pads at all? Maybe you live or drive through gravel type roads frequently? Hmmmm....Still have your dust shields on?

As far as the crunchy feeling, I say it's definitely the pads, rotors. The chewed up surface is causing that (fan effect) that was explained earlier. Changing out the pads/rotors should solve this.

[uiuc240]

I didn't notice any substantial benefit to the drilled rotors, and I've never had a bad experience with normal rotors. These, however, are grooved/pitted/rusted/flaking/fuxored and I'm not happy. I paid Don Nimi like $110 a piece for these things, and now they're toast...and it's pretty much impossible to turn drilled rotors (from what I've been told). Basically, then you're guaranteed the drilled areas will cause cracks.

I'm just going to get blanks and some nice pads and call it a day. Hopefully this will fix my glitch.

Thanks for the websites!

P.S. The Epson site doesn't suck...I'll send you a link later and you'll see that it's just fine.

[Dream240]

Yeah that's fine I guess, going with stock rotors. I'd say go with Hawk HPS pads anyways, pretty good and not too expensive. 51.20 plus shipping at this website:

http://www.ltbmotorsport.com/nissan240sx.html

Good deal.

So what about your typical driving areas, any gravel or off road driving that might cause a rock to get stuffed up inside your rotor causing the grooves and pitts? I'm wondering cause my old CD/slotted rotors looked brand new after my 2 year romp on em (minus the rust of course). Just curious.

[sleep]

Originally Posted by uiuc240

The wheels are cheap, old MB Motoring wheels...made by Prime for Discount Tire. They are 17x7 with approximately a +35 offset. They were painted by me last year. They simply hold the tires on the car...nothing special. I want better ones, but that costs money. :-)

Eric

wunna sell em? I need wheels to put my z brakes on asap....

[cdlong]

well, i couldn't find your page and just getting to a screen where i could type in a screenname was difficult.

good luck, feel free to post any other questions/problems.

[uiuc240]

Here's my page:

http://albums.photo.epson.com/j/Albu...&a=30160867&f=

And no...no gravel roads. And no...I'm not gonna sell the wheels right now. The tires are good, and I don't want to drop cash on new ones. Thanks for the offer, though. Well, wait, what's your price? If it's really good, I'll go for it...

Eric

[Dream240]

Originally Posted by uiuc240

And no...no gravel roads.

hmmm....I looked at your pics, so you do have big brakes on the front. Since that's the case, you're lookin at 68.00 (I think) for Hawk HPs pads. I think that's what I paid for mine from LTB motorsports. I was looking at your cross-drilled rotors and I noticed the blackness and a little of the grooves you're talking about. I also noticed that the rotors have ALOT of CD holes!!! The one thing I've always heard about CD rotors is that too many drilled holes causes weakness in the integrity of the rotor thus making it more susceptible to cracking, creasing, etc. So I'm betting that's the root of your problem Have you looked at the rotors closely to spot cracks and such?
I know what you mean about not being able to turn CD/slotted rotors, sucks!!

Car looks good BTW.

[sykikchimp]

Cross-drilled rotors don't help your braking unless you have crappy pads that out gas a lot, or over heat easily. Good pads like the HPS, or Axxis ultimates, or R4-S won't do that.

Slotting on the other hand has some good points without nearly as many bad. I still won't run them simply b/c they aren't necessary for what I do, and are way more expensive.

And buy OEM quality rotors. I've seen and heard of far to many non oem-spec rotors fail (literally rotor disconnected from the hub). I use G3000 Spec rotors from Cobaltfriction.com. All non contact surfaces are painted high temp black. Never had a problem with them yet on track. Great company, with awesome people who love road racing. Tirerack has a decent deal on plated 300zx rotors. A little more than the g3000 units. Both are under $60 ea.

If you want some really good street pads, Call up carbotech and tell them what your into, and what your looking for, and they will set you up. Awesome guys. I run their pads exclusively at the track.

[uiuc240]

Charles...you rule.

Thanks a ton, guys!