Brake pedal acting up!

[Megaman_js]

Okay heres what is going on. I have an 82 GT 5.0. Everyonce in a while the brake pedal will stiffen up. It stops fine actually better than normal. It only happens once in a while though. The rest of the time it still stops fine but the pedal is nowere near as stiff. Fluid is fine. Brakes were bleed properly when i changed shoes about 7 months ago. So what gives?

 

[superhuaman]

When was the last time you changed your brake fluid? It could be caused by environmental conditions (temp, humidity, etc.). Also, your rubber hoses may be subject to the same elements.

 

[rd]

It may be the power booster or the booster check valve, that's at the vacuum line connection to the booster.

 

[superhuaman]

I assume you're not leaking any brake fluid. Your seals in the master cylinder could be starting to wear out.

 

[Megaman_js]

I have changed the fluid almost a year ago. How often should it be changed? Vacuum line seem fine. Any other tests? It only seems to do it when i am cruising. Like on the highway and then i brake. Not really around town in stop and go type driving? It doesnt happen often enough to really concern me but i would hate to have my brakes go out while i am cruising down the highway!

 

[Black1987Stang]

I got the same exact thing...have no idea what it is though

 

[superhuaman]

I guess since it stops fine all the time, just that thepedal is stiffer sometimes, then it is probably a leaky booster. I don't know what I was thinking before. Oh, and you should change your brake fluid completely (flushing) about every 1-2 years. So you are ok there.

 

[04sleeper]

I would guess a bad brake booster or bad master cylinder.

 

[Megaman_js]

Thanks for the info. I am planning on going to all wheel disn in the near future, which master cylinder and booster would you guys recommend putting in? Would a 94-95 fit or a 96+ or would I have to stick with a fox?

 

[Megaman_js]

Ttt

 

[superhuaman]

Since you have an 82, I would recommend the 85 Lincoln Town Car master cylinder. It has a 1" bore, SAE threads (not metric), and a metal reservoir. It will look 'stock' on your 82, and you won't have to reflare to use metric tube nuts. You should be ok with your Fox GT booster. What brakes are you going to get? You could use: 4 lug 10" rear disc, stock 10" front; 4 lug rear disc, 73mm 11" fronts (with 87-93 v8 spindles); 5 lug 11" front/10.5" rear GT; or 5 lug 13" front/11.65" rear Cobra. And of course the 5 lug you need the 94-95 spindles. Don't get the 96-up ones. Although they are better with bumpsteer, they will cause wheels wider than 17x8 or 9 to not fit.

 

[Megaman_js]

Thanks for the info. I have not decided if i am going to go with a 4 or 5 lug brake setup. I would like to go 5 but i will see when i can afford decent rims as i have 4 lug right now. As far as looking stock under the hood i dont care to much for. If i can go with a plastic cylinder then i would rather do it that way. Will a 94+ not bolt on or are there mods needed? If they are a pain then a good booster of a 86-93 should do fine also right?

 

[superhuaman]

I only suggested the fox booster because i figured you already had it. If it's not enough, you can use a 94-98? I think V6 booster (the V8's were hydroboost). If you don't mind having a plastic brake fluid reservoir, you can use a 93 Cobra mc (1" bore), 94-95 Cobra mc (15/16" bore) or 94-98 GT mc (1-1/16" bore). But they all have metric threads, so you can't use your existing brake lines. You will need adapters.

I would recommend an 86-93 V8 booster, unless your cam is low-vacuum, then get the SN95 booster. The Cobra booster is too much of a pain to fit, plus most people think it makes the pedal too soft anyway.You will also probably need a 3-2 port conversion adapter kit, to let you plumb the new mc. It won't give you the metric adapters, though. I recomment the metal town car mc because you don't have to mess with finding tube nuts or adapters. But if you want the plastic reservoir, go with the 93 cobra unit, because it has a 1" bore, so its in the middle of the range. If you don't like it then it won't be totally horrible. But I love mine, with only a '90 booster.
More info, go to www.sn95brakes.com, it's where I learned all this stuff.

 

[Megaman_js]

Ya, i will only replace it if it is actually what is going out. I dont really see anything else for me to check. Fluid is fine, Vacuum is fine, all hoses are fine, no leaks anywere. It must be either the MC or Booster. Figure hey if i am going to replace it may as well go a step up right!

 

[superhuaman]

:Word:

New MC, junkyard booster
BTW, if you use a 3-2port conversion and a rear disc MC, you can still run your rear drum brakes with it! The prop valve will still work properly by limiting pressure to the rear brakes. It kind of helps to spread out the cost of the rear disc brakes. I'm running it this way on my car right now. The pedal is a bit spongy, but I think since the rear caliper bores are bigger than the wheel cylinder bores, it will firm up when I go to rear disc.

 

[Megaman_js]

That is good info to know! Thanks.