Brakes ATS Upgrade & Rear disc Brake issue

[Kabuki_notch]

Hey guys,

I couldn't find a solution to this issue searching (or I didn't look hard enough) I just recently swapped my car from Cobra front brakes and Rear drums to ATS Calipers, Taurus rear calipers, stainless braided hoses, new rear lines, 93 Cobra booster, 94/95 GT M/C all brand new parts. we bled the brakes over the weekend and got all the air (I think) out of the lines. I was finally able to take the car out today and I'm experiencing some problems.

With the engine off, the pedal is stiff with a little give.
With the engine On, pedal straight to the floor but pumping the brake a bit it hardens up.

I took the Car around the block and the pedal was going straight to the floor (unsafe to drive) so I got it back home and noticed the Booster is making a Whooshing sound and the pedal takes a bit to come up, seems to only do this when the engine is running, Vacuum leak?

I'm thinking there could still be air in the lines, potentially a bad M/C or booster these are all brand new parts I know that doesn't mean anything but it's unlikely. I have a brand new 93 cobra M/C I could swap out if I need to.

Anyone have any suggestions or obvious things I might have missed, I checked for leaks and nothing was evident.

 

[Mustang5L5]

Could be a few things. Tough to remote diagnose brakes because how the pedal feels and reacts tells you so much.

I agree it’s a mechanical issue somewhere. Possibly a leak that you haven’t noticed yet, as it doesn’t take much for the pedal to drop, especially when you have booster assist.

Could also be a faulty MC. Did you bench bleed the MC?

Could also be air, but usually if the pedal is rock hard with engine off that’s a sign all the air is out. Is it hard at the top of the pedal stroke, or does it depress a tad and then get rock hard? The later would still indicate air, or some other sort of “gap” in the system like a piston not fully extended or a caliper not seated fully.

 

[Kabuki_notch]

Thanks for the response Mike,

I bled the M/C in the car, wondering if the pitch when bleeding left air in it. It could also very well be a vacuum leak I had the upper intake off for some cable management and maybe left something unhooked.

I Just went outside and had the car running, I had one cracked vacuum hose I replaced but I noticed when I push on the Brake pedal and let off the idle goes up, so maybe I missed something else

 

[Mustang5L5]

I bled the M/C in the car, wondering if the pitch when bleeding left air in it. It could also very well be a vacuum leak I had the upper intake off for some cable management and maybe left something unhooked.

The only way i've managed to successfully bleed the MC on the car is to jack the rear of the car WAAAAY up to get the MC level, otherwise it typically traps an air bubble in the front of the MC.

While i don't want to defacto say this is the source of your issue, i would keep this in mind as oyu work through everything.

I don't think what you describe is a booster or vacuum leak. Typically with those, the pedal is hard as you lack assist. Since the pedal goes to the floor, that sounds like air/leak/MC.

If it was me, based on what you wrote here, i would bench bleed the MC. I know it's a PITA so definitely rule out leaks first. Only takes small weeping from one fitting to make the pedal sink to the floor. I just experienced that myself this past week. Pedal to the floor and the source of the leak was just barely oozing out.

 

[Kabuki_notch]

Thanks again for responding, I got a lift so makes things a bit easier when pulling the wheels etc, I'll get the car up in the air tonight pull the 4 wheels and check every fitting/connection and test again, if I'm still having issues I'll pull the MC and bench bleed it, just slowly check the boxes, I really don't want to pull that booster again

 

[Kabuki_notch]

update,

I checked every fitting twice, removed the M/C and bench bled it outside the car, manually bled the brakes and glad to say the brakes are holding no more pedal to the floor, I also noticed the 3-2 port adapters were leaking a little bit so it could have been a combination of it all.

 

[Mustang5L5]

It doesn't take much of a leak to get the pedal to sink steadily. glad you got it sorted.

 

[Kabuki_notch]

I'm back! Any idea what would cause this? Don't mind my holy shoes and header leak I need to fix


View: https://youtu.be/3kgzo1b_Qag

 

[limp]

Are those church shoes?

 

[Kabuki_notch]

Are those church shoes?

You know it

 

[AeroCoupe]

There is a vacuum switch up under the dash for the cruise control. Should be attached to a bracket under there with a plunger that the brake pedal depresses when you are not on the brakes. Sounds like the hose from it to the vacuum tree or booster (cannot remember) has come loose, the switch has failed, or the hose has a crack.

 

[Kabuki_notch]

There is a vacuum switch up under the dash for the cruise control. Should be attached to a bracket under there with a plunger that the brake pedal depresses when you are not on the brakes. Sounds like the hose from it to the vacuum tree or booster (cannot remember) has come loose, the switch has failed, or the hose has a crack.

dude! Thank you! I completely forgot about that I removed the cruise control stuff in the drivers side fenderwell and left the switch..

 

[Mustang5L5]

If you pulled that stuff out, you likely already removed the vac line that the switch runs too. It runs to the servo motor and then to the vac tree. Removing and capping the vac line labeled c/c should solve that problem if it is the source of the leak.

Otherwise could be booster leak

 

[Kabuki_notch]

If you pulled that stuff out, you likely already removed the vac line that the switch runs too. It runs to the servo motor and then to the vac tree. Removing and capping the vac line labeled c/c should solve that problem if it is the source of the leak.

Otherwise could be booster leak

Thanks Mike / Aerocoupe, I'll check the cruise vacuum dump, really hope it's not the booster it's brand new, wasn't the most fun I had working on my car putting that thing in..

 

[Kabuki_notch]

Booster, order a new one! Got the old one out tonight new one will be here later this week

 

[AeroCoupe]

Well that sucks but at least you know it will be fixed.

 

[General karthief]

Booster, order a new one! Got the old one out tonight new one will be here later this week

I knew that.

 

[Kabuki_notch]

got the new booster in today issue is resolved. Thank you everyone for your help