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Author
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Topic: Some braking questions.
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mikesmustang
Journeyman Posts: 4
From: Bountiful, Ut, USA
Registered: Oct 2003
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posted 10-01-2003 08:57 PM
   
I just recently replaced the wheel cylinders in the front drums of my '65 mustang, and I have changed the master cylinder. Now when I have not driven overnight or in a long while the brakes feel good (for no power brakes). But if i have driven for a while the brake pedal seems to be really high and hard. I press a little harder and the pedal does not move that much but it still stops. So I was wondering what could be the problem if there is a problem?Side question... my stoplight switch likes to come on a few minutes after I have stopped driving. So I have to unplug it and plug it back in when I drive. Because it works correctly when I drive. So do I need a new switch or what could I do? Any suggestions welcome.
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kcode
Gearhead Posts: 2623
From: alvaton,ky,usa Suburb of Bowling Green, M&M #79, MCA #29208
Registered: Jun 99
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posted 10-01-2003 11:08 PM
First off, welcome to M&M.Probably wouldn't hurt if you give us a little bit more information on your brakes. What type of master cylinder do you have, is it still the stock circular shaped or did you go with a dual cavity? I'd rather have a hard brake pedal than a soft one, especially if it still stops the car. 65's weren't known to have the best brakes. As for the brake light switch, is it mounted on the brake pedal or the master cylinder? If it is on the pedal, replace it, they are cheap. Its only a micro switch and yours is probably weak, I have taken them apart and repaired them but it was because you had to stand on the pedal just to get the brake lights on. ------------------
Mike Golliver
MCA Gold Card Judge-Modifieds
65 Kcode coupe 347 stroker modified 5-speed MCA Retired
66 convertible-3 dueces and a 5-speed with a 289
89 T-Bird Super coupe
01 Mustang GT Convt
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68RCodeConv
Journeyman Posts: 9
From: Houston, TX, Harris
Registered: Sep 2003
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posted 10-02-2003 04:17 PM
It sounds like your master cylinder has a slow internal leak. When you drive you "pump up" the pedal and all is fine. When you stop driving the pedal slowly drops because of the internal leak in the MC. The pedal drops far enough to activate the brake lights. I would replace the MC.
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adragon8u
Gearhead Posts: 795
From: oceano, Ca. USA
Registered: Mar 2003
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posted 10-02-2003 04:35 PM
If you just replaced the m/c with a new one, i wouldn't expect the internal leak. what I would suspect is air in your lines which would cause the "pumped up" pedal after driving. Did you adjust the brakes after doing the replacement? it almost sounds as if they may be over adjusted and that's why they feel "correct" after sitting but no travel when pumped up.------------------
66 coupe
289
C4 auto
90 ranger 2.3
95 Aspire
"someone who knows how will always have a job working for someone who knows why"
http://webpages.charter.net/adragon8u/mystang
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460-67Stang
Gearhead Posts: 195
From: Southern Ohio, USA
Registered: Feb 2001
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posted 10-02-2003 10:43 PM
quote:
Originally posted by adragon8u:
If you just replaced the m/c with a new one, i wouldn't expect the internal leak.
Was the m/c new or a "rebuilt" AutoZombie (or similar) unit? "Rebuilt" m/c's can sometimes have small rust "craters" at the bottom of the bore where water previously colleted and ate at it. This can cause the fluid to slowly bypass the newly installed rubber plungers and such. Yes, this has happened to me twice now. I'm to the point that I dissasamble a m/c before I install it just to check.
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adragon8u
Gearhead Posts: 795
From: oceano, Ca. USA
Registered: Mar 2003
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posted 10-02-2003 11:22 PM
quote:
Originally posted by 460-67Stang:
Was the m/c new or a "rebuilt" AutoZombie (or similar) unit? "Rebuilt" m/c's can sometimes have small rust "craters" at the bottom of the bore where water previously colleted and ate at it. This can cause the fluid to slowly bypass the newly installed rubber plungers and such. Yes, this has happened to me twice now. I'm to the point that I dissasamble a m/c before I install it just to check.
Good point, well taken. thanks  ------------------
66 coupe
289
C4 auto
90 ranger 2.3
95 Aspire
"someone who knows how will always have a job working for someone who knows why"
http://webpages.charter.net/adragon8u/mystang
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mikesmustang
Journeyman Posts: 4
From: Bountiful, Ut, USA
Registered: Oct 2003
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posted 10-03-2003 04:57 PM
FYI
It is an autozone rebuilt
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RonnieT
Gearhead Posts: 637
From: Port Allen, La. 70767
Registered: Jun 99
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posted 10-03-2003 10:18 PM
Two things come to mind for this problem to me. The first thing would be the return springs are weak and not pulling the shoes back in, after it sits awhile the shoes slowly retract. The second thig would be the residual pressure valves sticking. I would lean towards the springs being weak. Well I just read your post over, if you do not unplug the brakelight switch how long do they stay on? will they go out after awhile? This would make me think it might be the residual pressure valve hanging up, the springs are pulling the shoes back and pressuring up the lines, making the brakelights come on, I am assuming this is a pressure switch on the master cylinder for the brakelights. ------------------
Ronnie
69 mach1 351W-4V engineless at the time!
70 Torino GT 351C-4v with a "shaker"
Mustangs and More Member #23
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mikesmustang
Journeyman Posts: 4
From: Bountiful, Ut, USA
Registered: Oct 2003
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posted 10-04-2003 02:41 PM
The switch is on the brake pedal, and the lights stay on until the battery is dead. So I dont know whats going on.
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kcode
Gearhead Posts: 2623
From: alvaton,ky,usa Suburb of Bowling Green, M&M #79, MCA #29208
Registered: Jun 99
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posted 10-04-2003 11:09 PM
Mike,
Replace the switch, they are cheap. Alot cheaper than a dead battery.Mike
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mikesmustang
Journeyman Posts: 4
From: Bountiful, Ut, USA
Registered: Oct 2003
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posted 10-05-2003 10:59 AM
I will try that.
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