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Front brakes overheating

garyp

Jr. Member
Joined
Mar 13, 2011
Messages
92
Loc.
Germantown
Just installed new vaccum booster, and now the front brakes are sticking and smoking hot after 10 minutes of driving. I measured the pin on the booster and it has a little clearence from the master cyl. Any trouble shooting ideas?
 

ransil

Bronco Guru
Joined
Sep 6, 2003
Messages
8,122
Quick is to put washers between the booster & master cylinder to make sure there is enough clearance

Sent from my Galaxy Nexus using Tapatalk 2
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,275
The booster is the only change you've made? And you've been driving it extensively before the addition?

No chance there's a residual pressure check valve in place in the master cylinder?

Sounds like ransil's idea is your best first step though. Space it out just to make sure.
When you start the engine, does the pedal drop at all even without your foot on it?

Paul
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Might want to adjust the pin so it has just a little more clearance. The stock measurement for the pin height measured from the MC mounting surface on the booster is about .830-.895
 
OP
OP
G

garyp

Jr. Member
Joined
Mar 13, 2011
Messages
92
Loc.
Germantown
Quick is to put washers between the booster & master cylinder to make sure there is enough clearance

Sent from my Galaxy Nexus using Tapatalk 2

Exactly what I thought about doing, and checking the rear drum adjustment.
Thanks
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,275
Yeah Gary. Any updates?

Have you started your own thread too yet Paul? Or is this your first foray into finding the cause/cure?

Paul
 

Bronco Paul

Full Member
Joined
Nov 18, 2006
Messages
266
I've looked around and the only solution I've found was to add washers between the firewall and booster bracket to relieve pressure off of the brakes. This sounds like a good fix but you would think at this point they would have perfected that bracket mechanism by now...a fix is just that...a fix. Things should not need a fix, they should be engineered better. I know that in some of the Ford pickups they required a different rod for vacuum assist than the non-powered in the master cylinder....any chance of this for the Bronco? Was there any difference in the rod that connects to the brake pedal?
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,275
I think the spacers are more to adjust the angle for clearance with either the fender, the hood, or the engine components.
For dragging brakes the cleaner method would be to either adjust or modify the brake rods (there's at least two that are important here) to relieve any pressure on the master cylinder's piston.

The other mention of spacers is usually between the master and the booster to accomplish the same thing as shortening the rod(s).

The pedal-to-cantilever rod is sometimes adjustable. Sometimes it's a cut-to-fit in the original kit due to there being so many slight differences between one Bronco and another.
The booster-to-master rod is almost always adjustable to a certain degree, but there are different length rods too, depending on which booster is used.
Ether way though, there should be at least a few thousandths clearance (I think the spec is like .050" or so?) between the rod tip and the back of the piston.
So when mounting the master cylinder, if there was tension pushing on the piston before the body of the master bottomed on the booster flange, then the rod needs to be shortened. Or the master is wrong and has too shallow a piston recess for that particular booster.

The pedal rod is perhaps less finicky, but it still can't have any pressure against it when the bracket is bolted to the firewall. If it does, things could go wonky in a hurry.

Did you just install this Paul? Did you buy a kit or piece it together? Was the kit new or used?

Paul
 

Billsboat

Sr. Member
Joined
Apr 3, 2013
Messages
461
Loc.
Rowlett tx
Don, had Gary taken your advice he may not have posted his question. I'm guessing this is what you would have preferred? But if he had not posted, I and I assume many others would not have had the bennifit of reading all the responces to his question.

Because I'm not having break problems I would have not searched for a solution, but now I know much more about this topic that I other wise would have. Thanks for your question Gary! Pluse for me I enjoy reading what people are doing in real time.
 

Bronco Paul

Full Member
Joined
Nov 18, 2006
Messages
266
Hi Don...thanks for being mean. Merry Christmas...maybe this year Santa will bring you a heart.
 

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
Don has developed quite a reputation for being less than personable. I assume a giant chip on his shoulder causes him to talk down to others perhaps in an effort to make him feel better about his miserable existence. Keep in mind this is an assumption as I do not know the fellow personally and, judging by his demeanor, have not desire to do so.

Though I have addressed the issue with him before in private, he obviously doesn't care to change his ways. I am still waiting for him to contribute to our community in some form other than telling folks to learn how to use the search function.

Don, please do everyone here a favor; pack up and move over to pirate so you can tell folks there to use the search function. Your usefulness on classicbroncos.com has expired.

Paul, let's get together next Thursday and take a look at those brakes! I know how it feels to be between a rock and a hard place with these brake systems.
 

Bronco Paul

Full Member
Joined
Nov 18, 2006
Messages
266
Sure thing Mike! lol...and Don...it's not that we don't know how to use the search...it's just that when we're searching we're looking for some starting places to do our initial troubleshooting and most of the time it's just after the problem has attacked us and we're in cool down mode...which is third in line after panic mode then pissed off mode. I personally go from thread to thread looking to see if someone has the same symptoms and then to see how they solved them. This thread was not solved...so I bumped it to see if garyp would reply back as to whether or not he solved his issue and how he did it. My issue turned out to be the old water in the brake lines deal...at least that's what it looks like now. So I've drained the lines, cleaned the master cylinder, and bled the brakes. Now the brakes are not dragging...so...it's test drive time!
 

Bronco Paul

Full Member
Joined
Nov 18, 2006
Messages
266
brake fluid is hygroscopic so it absorbs and retains water and it becomes saturated. Excessive braking also causes the fluid to boil which creates steam from the air that has crept into the master cylinder and once the steam cools it separates into water and air...that's why you're supposed to change your brake fluid like every couple of years. I got lazy...I should have looked at the fluid...it was very cloudy and needed changing.
 

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
Same reason the bottle will mention shelf life once opened. Glad you got it fixed. However, i would have thought water would cause spongy brakes, not sticky.
 

Billsboat

Sr. Member
Joined
Apr 3, 2013
Messages
461
Loc.
Rowlett tx
Thanks for the explanation paul. I too have heard to change break fluid every so often...never knew why, now I know. I'm also gonna take a look in my master cylinder.
 

Bronco Paul

Full Member
Joined
Nov 18, 2006
Messages
266
Hey...just to update...this is what my fluid looked like (even after I drained most of it...) and the rust that had formed in the master cylinder. Yes...I know...shame on me for letting it get THAT bad!

2013-12-14155017_zps30b84945.jpg
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2013-12-14155106_zps1d095d85.jpg
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2013-12-14155033_zps1b5e8cf9.jpg
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