too much heat=brake pedal stiff??

[NemeGuero]

alright, so refer to this post to see my set-up
http://www.zilvia.net/f/showthread.php?t=93903
since then, I have also thermal wrapped my downpipe with header wrap.
driving around for no more than 10 minutes, my brake pedal gets hard. I thought that with all the heat shielding and stuff that my brakes would be fine, but I guess not. I can feel the pressure on the rotors and my rims themselves are hot to the touch. Under the hood, I can touch the BMC and all the lines coming off it, but they aren't hot at all. the only place the lines are hot is along the firewall, but even that isnt too hot. I've seen set-ups with less heat protection than mine and they seem to run fine.. why then is this happening to mine?

please help. any ideas and suggestions will be appreciated

*I am also taking Russ's advice from the previous thread about tripling the heat shield stuff. Thanks

[Ritz S14]

When you get a stiff pedal. Go park it, jack up all the wheels and see if they spin freely.

You might have a seized caliper.

Edit. Are all the wheels hot?

Having a boosted car shouldn't have anything to do with the wheels being hot. Every time I drive my car, I could never seem to get my 26mm calipers warm(regular driving).

What kind of brake fluid are you using?

[Phlip]

this thread DESCRIBES a different set of symptoms:
http://www.zilvia.net/f/showthread.php?t=31732
... but at MrMephistopheles' advice, I did the same thing, after getting another Brake Booster from Russ and being assured that the MC was in good shape, replaced the front calipers and ALL pads.

For safe measuring, I would reccomend so thoroughly bleeding the fluid that you're effectively changing it.
... smooth sailing since.

[zero.counter]

I would bleed all lines first and see what happens. Is the pedal slowly sinking to the floor when you step on it? If so, then look into the MC suggestion.

[theicecreamdan]

anytime you take the time to bleed you should spend the extra couple bucks to completely change the fluid. IMO

[zero.counter]

anytime you take the time to bleed you should spend the extra couple bucks to completely change the fluid. IMO
Good point.

[NemeGuero]

yes, all 4 rims are hot..
I'm using dot 3 right now but my next variable elimination involves flushing the system and using dot 4. I already bought the fluid, just need the time and a bleeder.
the pedal is soft when I haven't driven for very long.. and only gets stiff after a while. I can feel the car being 'locked' 'cuz me and a buddy couldnt push the car at all after 10 mins of driving. But after its cooled down, drives fine and rolls fine.

PHLIP, are you suggesting I have a bad MC?

[Ritz S14]

IMO I've heard of a similar situation.. where at one time a different type of fluid(trans?motor oil?) has been used in the BMC.

So. Before you swap out the BMC, like someone suggested.. Drain all the brake fluid, and start with a fresh bottle of DOT 3 or 4.

[NemeGuero]

I can't really visualize how diff types of fluid can cause my pedal to be stiff. In fact, anything other than kinetics leaves me confused about the solution.

[kazuo]

I think I know the solution... since I had the exact same problem.

Adjust the length of the rod that goes from the BMC/Booster to the pedal. There's a 10/12mm locknut IIRC, loosen it and lengthen the rod until the brakes stop heating and locking up.

Took me about 2 tries to get it right, basically loosen & adjust it until the brakes stop locking up. If the pedal feel for you is too mushy at the setting where it stops, let it fully cool and then carefully adjust it, bit by bit, until you have decent pedal feel & it doesnt overheat & lock the brakes.

I had the same problem on my car when I did manual swap and changed the brake pedal.. took me awhile to figure out the problem.

Call me up if you have any questions Evan, peace

[NemeGuero]

thanks dawg.. guess i'll do that AND bleed/flush the system

[NemeGuero]

What happens when the piston is as far backset as it goes and my brakes are still dragging? It helped, alot, but I can still feel the brakes getting stiffer and after driving for a little while, I can't push the car very easily. Like I could with the BMC completely dis-attached. It passes the roll test (drive up a slanted drive-way and let her roll back) but not the push test(comparitive "nudging before and after to see if it'll roll on a level road.)

I haven't flushed or bled the system yet, but I don't see how those 2 things could prevent my car from rolling. Thanks

[kazuo]

Try adjusting it a little more.

Drain/refill/bleed the system as well.

Good luck

[NemeGuero]

its basically as far as it goes..

[NemeGuero]

Alright, I'm about to give up right now. So here is my update:

I realized that I wasn't using the check valve. When i had swapped Boosters the one I used was from an s13 so I had to modify the vacuum line and forgot all about that little one-way valve. So I put that in thinking all my woes were cured. WRONG.

I bled the brakes once per corner and went for a drive. The pedal was still stiff but I thought it was because I had just bled them. Then it got increasingly stiff and about an inch or less of pedal depression brought my car to a stop.

The car would still roll. I went up an incline, left it in neutral and it rolled back.
So I continued to drive for about 10 more minutes.

Pedal didn't loosen up but I also could tell the brakes weren't dragging. After I let off the gas, the car didn't drag.

So I pull up in my drive-way.. neutral and she doesn't roll back. I depress the brake pedal and it softens up. After I let off, she starts rolling backwards. I pushed the pedal in again and it was softer but still firm and she rolled backwards more smoothly.

Is the check-valve bad? Vacuum leak? The MC piston is as far recessed as it will go. And I'm pretty sure the line isn't leaking.

HELP! This is the only thing keeping me from driving my car and it sucks!

[CHARLIE2020]

I sorta just skimed threw this, but as someone mentioned above did you try adjusting the brake pedal pushrod via the locking nut and or mess with the power brake booster pushrod like someone on this fourm mentioned adjusting the bullet cap shaped nut that enters the brake master cylinder?

Do you have anyplay in your brake pedal are is it just really irm from the get go?

[CHARLIE2020]

Sounds like the pushrod is pushed to far in and is engaging the brakes allready this will be even more pronouced if using the 1 1/16" BMC

[CHARLIE2020]

I think I know the solution... since I had the exact same problem.

Adjust the length of the rod that goes from the BMC/Booster to the pedal. There's a 10/12mm locknut IIRC, loosen it and lengthen the rod until the brakes stop heating and locking up.

Took me about 2 tries to get it right, basically loosen & adjust it until the brakes stop locking up. If the pedal feel for you is too mushy at the setting where it stops, let it fully cool and then carefully adjust it, bit by bit, until you have decent pedal feel & it doesnt overheat & lock the brakes.

I had the same problem on my car when I did manual swap and changed the brake pedal.. took me awhile to figure out the problem.

Call me up if you have any questions Evan, peace

Its a 14mm locking nut and here are the ways to adjust:

Turning the pushrod with needle nose pliers "counter clockwise" will increase the amount of slack (for lack of a better word) in the brakes, i.e. the brakes wont be pressing against the rotors as hard the more you adjust in this direction.

Turning the pushrod with needle nose pliers "clockwise" will decrease the amount of slack (again for lack of a better word) in the brakes i.e. the brakes will be pressing against the rotors harder is adjustment is made in this direction. (Becareful adjustment in this direction as you can make the brakes drag and you can also make the pushrod fall out of the brake pedal if you run all the threads threw)

Hope this helps.

Depending which master cylinder you choose adjustment of this device will vary from master cylinder to master cylinder.

[NemeGuero]

I'm using the 15/16s master cylinder. The pushrod with the ball head is as recessed as it will go. (All the threads are inside the pushrod head).

As I understand this is as unengaged as the piston can be. It is firm when I drive away.. but there is at least a good 4" of travel before the brakes get stiff. Afterwards, they get increasingly harder.

[CHARLIE2020]

I'm using the 15/16s master cylinder. The pushrod with the ball head is as recessed as it will go. (All the threads are inside the pushrod head).

As I understand this is as unengaged as the piston can be. It is firm when I drive away.. but there is at least a good 4" of travel before the brakes get stiff. Afterwards, they get increasingly harder.

You shouldn;t really mess with the ball head pushrod inside the PBB, you should adjust the brake pedal adjustment under the dash area in the proper direction as listed above.

[psychoblue23]

Dood I feel your pain. I jsut went through this problem in my old civic. I upgraded the brakes to a GSR setup and changed everything. Calipers BMC booster and it had the same problem. Everything was installed and bled correctly but I couldnt get the calipers to stop locking up. I even relplaced the calipers too. I couldnt figure it out so I just sold the car... :( since I have been wanting a 240 it wasnt a big deal. If you get this figured out make sure you post what you did to resolve the problem.

[NemeGuero]

Well either way, I doubt its the piston rod from the booster since its recessed all the way.

any other ideas? I don't plan on selling my car. I have a new booster and a new BMC I can try out.. which I guess is the next step.

[NemeGuero]

Was your civic boosted?

[CHARLIE2020]

Well either way, I doubt its the piston rod from the booster since its recessed all the way.

any other ideas? I don't plan on selling my car. I have a new booster and a new BMC I can try out.. which I guess is the next step.

Hello what about the brake pedal adjustment have you messed with that?

[NemeGuero]

There is no need to. The pedal moves before there is any pressure on the pushrod.

[psychoblue23]

Was your civic boosted?

No boost just an LS. I was told the same thing about adjusting something inside the car, I was told that the pedal was not adjusted correctly so it would not fully release the brakes. If you have not tried that I guess thats my only suggestion. Like I said I was totally stumped, and I couldnt drive the car cuz after about 10 minutes, the wheels would start smoking haha. Hmm Yea I tried everything.. I even put my car on a slight incline and tried to see if ti would roll, but the brakes wouldnt let it. When I would push the brake pedal alllll the way to the floor it would sorta pop like something was not right, then the car would slowly roll back... then tighten up again. I would try those new parts you got...

EDIT: Sorry noticed you already thought of that idea

Good luck bro...

James

[NemeGuero]

They aren't dragging. But to make everyone happy, I'll set the pedal pushrod to factory specified length.

[NemeGuero]

Vacuum leak appearantly. I measured the length of the pushrod under vacuum and it was on the low side of factory spec but within the range.

Put the MC back on.. noticed the vacuum line wasn't over the "hump" in the pipe... pushed it on.. went for a drive...

I think it's fixed. I'll report tonight or tomorrow after I take it for an extended drive to determine if it's it.

[NemeGuero]

It's not fixed.

Here is my update:
All 4 Q45 calipers and rotors installed
flushed brake fluid for dot4
replaced check valve

I can drive and then the pedal gets hard and brakes begin to drag. If I pull over, remove the vacuum line to the BMC it makes a loud hiss.. then the wheels are all free to roll and the pedal is soft again.

My guess is either the booster is leaking or the BMC has seen the end of it's days. I'm going to replace both this weekend.

All new brake system just to fix this problem... ohs well.

BTW.. anyone know where I can buy project mu brake shoes for Z32 ebrake?

[Ritz S14]

http://splparts.com/Parts/NissanShared/Brakes/Pads/default.asp

all the way down.

[NemeGuero]

Thanks! They're a bit more then I expected though..

[Ritz S14]

OEM ones cost a lot more.

[infinitexsound]

forgive me if im wrong... but arent u rockin a ka-t... if ur brake lines are getting heated wouldnt that create ur brakes to lock up... post pics... of ur engine bay.. maybe ur lines are too close to the DP .. neme..

[NemeGuero]

That's what I originally thought.. I installed this shield though as you can see in this thread..
http://www.zilvia.net/f/showthread.php?t=93903

And I made it all the way from San Jose to Berkeley without a problem.
When I drive "spirited-ly" they'll lock. I'll have to pull over, remove the vacuum line to the booster, and then they'll losen again.

This makes me think it isn't heat related..

I dunno man.

If replacing the MC and booster doesn't fix this.. it's going to the shop.
And if they can't fix it.... I don't even want to think about it.

[neilsan]

I wonder if the check valve for the brake master vaccuum pod isnt going bad from boost, pressurizing the tank instead of keeping it hold a vaccuum. i think that would just make it harder to stop, though, instead of push on the cylinder piston itself and stop FOR you. ...i think. If heat expanded the fluid enough to lock your brakes, it should instead back up into the resivoar.

edit: it cant be my first suspicion.

Its got to be the pedal isn't adjusted properly... There's a critical spot where the piston *just* goes past the hole in the bottom of the resivoar. If it's not coming up past that hole, when the fluid heats up, it expands, and without any place to go it is pushing your pads against the rotor. The turbo may not have as much of an effect as you suspect, the calipers themselves can get up to like 600° if youre doing hard braking. It's probably a combination of both, the turbo is heating the lines at the BMC and its pushing on the pads a little, then on the highway the drag is heating up the calipers and the fluid is expanding from that end of the system too.

readjust your pedal. The fix to a problem has to make sense, and that makes lots of it. if adjusting doesnt fix it its most likely the bmc is grody or rusty inside and the piston isnt releasing into its 'home position' properly.

Is there loose 'play' in the brake pedal before you feel resistance when its cold?

[EchoOfSilence]

it just sounds like something's clogged. If it's the vaccuum line that hisses, the BMC is either bad or the inlet is clogged. If the BMC hisses, the outlet on the other side of the vaccuum line is clogged.

however, this is just speculation