Have a Gen 3 Funco, typical setup with master cylinder, 4 piston calipers, and cutting brake. No leaks. Bled the brakes at all 4 corners and the cutting brake before this last trip and the peddle was hard, little air but not a ton. Went out last weekend and it was good at first but after about 5-10 minutes into ride, they peddle had no pressure and nothing at cutting brakes either. Ride later on and seemed like the brakes were pretty hard again then a little into the ride got very soft with practically no braking ability. No leaks that I can find. What could be going on? I know.............who need brakes right lol.
Brakes
- Thread starter Spark2678
- Start date
Bobalos
Well-known member
- May 5, 2021
- 6,108
- 5,009
My gut feeling........... Master is going bad.
and yea.......... who needs brakes. the only time I miss mine are when Im pulling into the trailer, I dont want to run into the cabinets I spent so much time building. LOL
Bob
and yea.......... who needs brakes. the only time I miss mine are when Im pulling into the trailer, I dont want to run into the cabinets I spent so much time building. LOL
Bob
Jtmoney714
Well-known member
- May 6, 2021
- 763
- 647
Do you have a residual valve?
- Thread starter
- #5
- Thread starter
- #6
Bobalos
Well-known member
- May 5, 2021
- 6,108
- 5,009
Yes, Master going bad. especially if its been over extended @ any point in its life.
this is a residual valve. some calipers & Wheel Cyls need them.
this is a residual valve. some calipers & Wheel Cyls need them.
Last edited by a moderator:
- Thread starter
- #8
What is the typical rebuild
Just get a rebuilt kit? I need to figure out what size it is, ie 3/4, 7/8, etc....
Dynamicdude
Active member
- May 25, 2021
- 109
- 63
What brand master cylinder? If CNC might be hard to find
- Thread starter
- #10
I replaced my CNC master cylinders with Jamar. They bolt right up. Certainly more expensive than a rebuild but the CNC parts kits are not available.
One other thing that can cause the pedal to do what you are describing is warped rotors. If there is warp in the rotor it knocks the pads and drives the pistons back into the calipers a little bit creating a gap between the rotor and pad which has to be filled on the first pump. Typically you can tell if this is part of the issue by pumping the brakes a couple times. If the pedal consistently comes up when pumped it might be "runout" from warped rotors. Testing for this cannot be done without the wheels rolling around. Bad or mis-adjusted bearings (front and rear) can also mimic this problem. Remember it's a dynamic problem that is hard to replicate in the garage.
One other thing that can cause the pedal to do what you are describing is warped rotors. If there is warp in the rotor it knocks the pads and drives the pistons back into the calipers a little bit creating a gap between the rotor and pad which has to be filled on the first pump. Typically you can tell if this is part of the issue by pumping the brakes a couple times. If the pedal consistently comes up when pumped it might be "runout" from warped rotors. Testing for this cannot be done without the wheels rolling around. Bad or mis-adjusted bearings (front and rear) can also mimic this problem. Remember it's a dynamic problem that is hard to replicate in the garage.
- Thread starter
- #12
Rotors might be slightly warped but I think they are ok.
7/8" bore CNC. See pic. Race ready makes a rebuild kit for 702 or 705 models which these are. But the rebuild kits in the pics on their site look different than then CNC rebuild kits that are no longer manufactured. Thinking just replacing, as said above with Jamar which is direct replacement. I can do EMPI too which looks like direct replacement and half the price, any issues? Why would it be the master cylinder if I am losing my cutting breaks too (no pressure)? Could they both have failed? PS...boots are off the cylinders because I was measuring.
7/8" bore CNC. See pic. Race ready makes a rebuild kit for 702 or 705 models which these are. But the rebuild kits in the pics on their site look different than then CNC rebuild kits that are no longer manufactured. Thinking just replacing, as said above with Jamar which is direct replacement. I can do EMPI too which looks like direct replacement and half the price, any issues? Why would it be the master cylinder if I am losing my cutting breaks too (no pressure)? Could they both have failed? PS...boots are off the cylinders because I was measuring.
Last edited by a moderator:
Bobalos
Well-known member
- May 5, 2021
- 6,108
- 5,009
Imho, Jamar all the way. I've had too many hit and miss with empi to go there. If I had no other choice, then yea.
Punchdrunk Monkey
New member
- May 5, 2021
- 570
- 723
Empi is the "Harbor Freight" version.......They're your brakes, you choose 
lincster
Well-known member
- May 5, 2021
- 667
- 484
Going the cheap route with a sand rail never works out.
Flattman
New member
- May 8, 2021
- 59
- 45
If it were me, I'd try the RaceReady kits. Look like they include the soft, wearable pieces and while I did purchase Jamar replacements for mine, I went back to revive my CNC's. I know there's not as many choices as there used to be but in my opinion, the CNC's are worth trying to rebuild if you can.