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Odd brake issue

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20 replies to this topic

#1
Dsm_alpha

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Updated:
So I wanted to update this thread after a lot of troubleshooting and comparing to a few other cars. Seems like the issue is actually related to the bigger 282 cams in the car. At idle the vacuum is not great and thus I am not getting much help from the booster. On deccel there is more vacuum and thus the car brakes better from speed.

I am going to add a vacuum reservoir, for now though I need to push harder on the pedal at low vacuum conditions


Original post:
A couple months ago I switched to a new set of J-hook rotors with hawk pads. The braking wasn’t great so I switched to the mx72 which improved it dramatically but I am having an odd issue.

When I let the car sit for a day or so the first time I get on the brakes it feels a little squishy and doesn’t stop hard. Once I have braked a few times and have some heat in the system it gets noticeably better and stops like the combo should. I have bled them a few times and do not see any air. Any thoughts on anything else to try? Anyone ever have warping of J-hooks? Fluid level is solid and no leaks. I also have the master cylinder brace.

Maybe I got a bad set? Might try a set of RB or DBA T3 5000 for street usage, anyone have experience with these? I love j-hooks but these suck for some reason

Edited by Dsm_alpha, 19 August 2019 - 07:15 PM.

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#2
Tim

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I have your set up and it Deff is always a little interesting the first time you push the breaks... but I’ve had no warping issues
 

 


#3
droptopp

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I run Jhooks with Project Mu pads.

Did you bed the new pads into the rotors ?

When I previously let my car sit for a year +/- they had a good deal of oxidation on them. Definitely needed another round of bedding to clean them off.
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#4
Dsm_alpha

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I bedded them a few times

#5
elf_cruiser

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Remove the plastic covering around the wipers and the brake booster. Then look/feel underneath for any brake fluid. I had a similar issue and it was a leaky master cyl. Otherwise double check the bleeder screws for leaks at all calipers, if just one of them is stripped it can cause this issue as well. Luckily they are easy to repair.

I doubt it’s a warped rotor or else it would be mushy every time you hit the brakes, not just after sitting awhile.
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#6
Dsm_alpha

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Remove the plastic covering around the wipers and the brake booster. Then look/feel underneath for any brake fluid. I had a similar issue and it was a leaky master cyl. Otherwise double check the bleeder screws for leaks at all calipers, if just one of them is stripped it can cause this issue as well. Luckily they are easy to repair.

I doubt it’s a warped rotor or else it would be mushy every time you hit the brakes, not just after sitting awhile.


Thanks - will definitely check this but the fluid level has stayed rock solid so not thinking it’s leaking. It feels better when brakes are warm. Ordered another set of rotors and pads to try as well.
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#7
elf_cruiser

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It only takes a few minutes to check and make sure. A few drops of leakage wouldn’t change the fluid level. However it could be a sign that air is getting into the master when the car sits, and is purged out after a few pumps of the pedal. Just an educated guess on my part, and it’s an easy thing to check.

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2010 GT-R - Matte Gray, AP/Carbotech, BSE trans cooler, BSE tune on ECUTek, H&R sways, AMSOIL, NASA-AZ TT2 and occasional DD
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#8
Dsm_alpha

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Checked the master cylinder and couldn’t find any fluid around it or brake booster. All the bleeders looked good, passenger rear looked like maybe 1 drop of fluid so cleaned it up and pumped brakes and didn’t see any additional fluid. Will keep an eye on it.
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#9
Dsm_alpha

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Took a few pics, to me it looks like uneven wear is occurring
7425C669-C6CB-46D4-8B11-EA30706BB595.jpeg DC00EA52-C754-4EE6-BA4E-C1D36D674870.jpeg
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#10
Yme

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For my own curiosity, what brand of J hooks do you have?


Edited by Yme, 04 July 2019 - 06:19 AM.


#11
Dsm_alpha

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AP Racing now - gonna switch to Alcon

#12
elf_cruiser

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Checked the master cylinder and couldn’t find any fluid around it or brake booster. All the bleeders looked good, passenger rear looked like maybe 1 drop of fluid so cleaned it up and pumped brakes and didn’t see any additional fluid. Will keep an eye on it.


Good news, yeah keep an eye on that rear bleeder and see if it’s wet again after a few days. Could be the culprit...
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1976 FJ-40 Rock Buggy - tube chassis, LQ4, 700R4, NP205, Rockwells, F&R hydraulic steering, Fox, Ballistic, lots of 4130, 7068, and AR400

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#13
Dsm_alpha

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Replaced with Alcon rotors and another new set of mx72. Stops a lot harder and now I can actually hit ABS with 285/345 Cup 2s.

Still have a little bit of travel at top of pedal, can this be adjusted out with the pedal?
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#14
haul s

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Do you have a master brake cylinder stopper already? If not, get it - I bet it will take out the slop on initial brake application.

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#15
Dsm_alpha

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I do have the stopper, gonna play with the adjustment of it and see if it helps.

The only thing is I still kind of feel like the pedal needs a bit more travel before it bottoms out to get full brake force but maybe I just need to bed the pads more. Right now I feel my foot stop but I want to press down further

Any thoughts? Should I mess with the pedal rod adjustment?

#16
Dsm_alpha

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So I ended up replacing the master cylinder as the pedal was still a bit soft for the first 1/3 of travel. Feels a ton better now. There was no fluid leaking but there were some scratches on the piston and piston bore so the seals must have been letting some fluid past.

Hoping this is the final solution as not having confidence in the brakes sucks.
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#17
thehelix112

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How old is your car? Crazy to need to replace mc already.. I more associate that with my Datsun days.

#18
Dsm_alpha

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How old is your car? Crazy to need to replace mc already.. I more associate that with my Datsun days.


It’s a 2009
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#19
Tim

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So I ended up replacing the master cylinder as the pedal was still a bit soft for the first 1/3 of travel. Feels a ton better now. There was no fluid leaking but there were some scratches on the piston and piston bore so the seals must have been letting some fluid past.

Hoping this is the final solution as not having confidence in the brakes sucks.


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#20
elf_cruiser

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How old is your car? Crazy to need to replace mc already.. I more associate that with my Datsun days.


You’ve only got a few more years, mate! Good news is that they are cheap and easy to replace!
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2010 GT-R - Matte Gray, AP/Carbotech, BSE trans cooler, BSE tune on ECUTek, H&R sways, AMSOIL, NASA-AZ TT2 and occasional DD
1976 FJ-40 Rock Buggy - tube chassis, LQ4, 700R4, NP205, Rockwells, F&R hydraulic steering, Fox, Ballistic, lots of 4130, 7068, and AR400

2001 Ford Excursion - V10, DD and occasional tow rig

facebook.com/DangerousEnterprises

Do want someday - Radical, 599 GTB w/FHP, 430 Scud, Superlite Coupe, FF Type 65 Coupe





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