Resolved 1985 GT brake pedal problems

[DienstXIV]

Hi Everyone,

I have a 1985 Mustang GT with the original front disk brakes and rear drums. When I press the brake in motion the pedal slowly goes all the way to the floor but when I am stopped the pedal seems to hold firm sometimes. I have checked the brake fluid and it seems to stay at the same level.

All my friends are telling me there is air in the brakes but it doesn't feel like that, it feels like a leak but I have pressed and pressed on the brakes and cannot find a leak or notice the fluid level going down.

Anyone have this happen? Could it be there is a place that leaks a little bit and holds the fluid and I just don't notice it?

Could it be something else? Any ideas are greatly appreciated.

Cheers!
Alex

 

[General karthief]

Master cylinder is 'bypassing' which means the fluid is being pushed around inside the master cylinder, ever change a master cylinder?

 

[DienstXIV]

Master cylinder is 'bypassing' which means the fluid is being pushed around inside the master cylinder, ever change a master cylinder?

I have owned the car since 2012 and I have not changed the master cylinder, you think I need to change the master cylinder?

 

[limp]

ower brakes?? Almost sounds to me like your booster is going bad?????

 

[AeroCoupe]

Bleed the brakes and get fresh fluid in there. That’s cheap and easy. If that does not fix it then it’s the master cylinder.

If the brake booster was shot the pedal would be as hard as a rock instead of assisted soft.

 

[Noobz347]

I have owned the car since 2012 and I have not changed the master cylinder, you think I need to change the master cylinder?

I think you need to put the thing on stands and inspect the entire brake system from master cylinder to each wheel/slave.

Get yourself a parts list together and then go to town.

Post up pics of anything that looks "spooky" so the guys here can help.

 

[General karthief]

I think you need to put the thing on stands and inspect the entire brake system from master cylinder to each wheel/slave.

Get yourself a parts list together and then go to town.

Post up pics of anything that looks "spooky" so the guys here can help.

Or laugh hysterically

 

[DienstXIV]

So I definitely think it's the master cylinder. Went to go change it and broke the brake lines going from the master cylinder to the proportioning valve block. I have gone to O'Reilly's and AutoZone and they both weren't able to get the correct fittings.

Does anyone know where I can get brake lines that will fit?

Thanks in advance,
Alex

 

[AeroCoupe]

You may need to make them. Fitting sizes on the MC are 9/16-18 and 7/16-24 and both are inverted flares.

 

[85GTStangGuy]

Does anyone know where I can get brake lines that will fit?

Never seen them sold separately.

Are they part of this kit??

Fits 1984-1986 Ford Mustang Front Brake Line Set MFB101 | eBay

MPN: MFB101. Mustang with front disc brakes, 5 pcs. 1984-1986 Ford Mustang.

www.ebay.com

You may need to make them. Fitting sizes on the MC are 9/16-18 and 7/16-24 and both are inverted flares.

I agree the primary is 9/16-18.... but could the secondary be 1/2-20, not 7/16-24??

Reference:

More Information for CENTRIC 13061043

More Information for RAYBESTOS MC39531

 

[AeroCoupe]

Could be. I swapped both cars to a SN95 MC and full Cobra setup years ago. O’Reillys (not 100% reliable) says it’s what I posted but….

https://www.oreillyauto.com/shop/b/brakes/brake-hydraulics/brake-master-cylinder/3bff094046ed/v/a/5472/automotive-car-1985-ford-mustang

 

[DienstXIV]

SOLVED
So thanks everyone, it ended up being the brake master cylinder. I ended up finding a guy at an O'Reilly's that wanted to help piece together parts for new brake lines from the master cylinder to the brake distribution block. Ended up going with 1/4 lines and some adapters. It was the only way we could get it to work.