2eighTZ4me Posted April 4, 2014 Share Posted April 4, 2014 Since I didn't get any response on the Wilwood sticky thread - I thought I'd try my luck with a fresh post. Have an extremely touchy pedal. There is no 'pushback' from the pedal at all. It goes down with very little effort and the car stops on a dime. Heel and toe braking is a non-option - the pedal is just way too touchy. I thought I had dropped the reaction disk in the booster (which I did) - so I bought a reman booster. Still the same problem persists. I can shake the old booster and hear the reaction disk bouncing around inside. The new booster - I cannot hear anything when shaking it (after adjusting the pushrod). Leads me to believe the reaction disk is still in its' proper place. Brakes have been bled ad-nauseum - nothing but fresh fluid coming out - not a speck of air. I'm running the Toyota vented setup up front and the MM 240SX rear. I do not recall if I removed the cones from the Wilwood or not. Would they (or the lack thereof) cause my pedal to be so touchy? Scratching my head over this one... Quote Link to comment Share on other sites More sharing options...
johnc Posted April 4, 2014 Share Posted April 4, 2014 Sounds like a reaction disk problem. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 4, 2014 Author Share Posted April 4, 2014 John - I agree. Is there any way to verify for sure that it's in and seated properly? I saw an old post of Blue's where he took the booster apart and fished the disk out - but it was an old post and the pictures were long since deleted. How do I get in to the booster? I still have my old one to play with. Quote Link to comment Share on other sites More sharing options...
socorob Posted April 4, 2014 Share Posted April 4, 2014 I believe the manual on xenons shows how to open it. Looks like you put half in a vice and then bolt a bar onto the cylinder bolts and basically unscrew it. Does anyone know if that's correct? I got a booster from rockauto and I didn't put it on the car for a long time from when I got it, and it looks like they put the 2 halves back together 180 degrees out. The tube for the vacuum is in the wrong place. Will that hurt anything? I will be finishing up the brakes and bleeding them in the next few weeks, and would rather take it apart now if there will be a problem than after I have everything full of fluid. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 4, 2014 Author Share Posted April 4, 2014 socorob - you can easily detach the master cylinder (full of fluid) and push it forward and out of the way to get the booster out if need be. No mess. Did it last week. Quote Link to comment Share on other sites More sharing options...
luseboy Posted April 4, 2014 Share Posted April 4, 2014 Checking the reaction disk is super simple. Remove the master cylinder. Look down where the pushrod comes out and there's a metal retaining disk. Use a screwdriver/pokey tool/etc. to gently pry this piece of metal out, and pull the pushrod out. The reaction disk is a piece of rubber that should be sitting on the inside end of the pushrod. Glue it in place and put it back together. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 4, 2014 Share Posted April 4, 2014 Blue (atlanticz) has pictures of everything. #3. http://www.classiczcars.com/forums/wheels-tires-brakes-s30/46506-reaction-disk.html Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 4, 2014 Author Share Posted April 4, 2014 Thanks NewZed!! That's the article I had looked at - but for some reason - the pics wouldn't come up. Thank you!! Quote Link to comment Share on other sites More sharing options...
Miles Posted April 4, 2014 Share Posted April 4, 2014 Verify that the push rod is properly adjusted. If it is too short the brakes will feel exactly like the reaction disk has fallen out. On my Wilwood 1 inch install, the push rod is adjusted with about 1mm space between the end of the push rod and the MC piston. As I recall the rod length measurement is 13mm - 15mm from the aluminum spacer on the booster to the end of the push rod. Remember that adusting the push rod out too far will cause your brakes to lock up (hydraulic fluid can not return due to the return ports in the MC being blocked). Search the brake section for "push rod adjustment" for methods and tips etc. Also, did you install the aluminum spacer between the booster and the MC? Recently another member here had the exact same issues as you and the problem was caused because he forgot to install the spacer. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 4, 2014 Author Share Posted April 4, 2014 Miles - yes - I do have the aluminum spacer in place b/t the MC and booster. I did my adjustments to the rod as you stated. I have maybe 1mm of play in there. I will re-measure the rod in the old booster once I get the reaction disk back in there tonight and see if it is the 13-15mm you stated. The pedal still comes on fairly high up - so I have to think the rod is adjusted 'close' - as the pedal doesn't drop to the floor before activating the brakes. Pedal 'height' feels totally correct - there's just no pushback on the pedal. I can hit it with my big toe and the car will stop on a dime. It's not so much when/where they activate - it's how little pressure I have to use to get them to work. I'm used to having some pedal pressure to work with in order to stop smoothly - there's just no pressure and all stop.... Quote Link to comment Share on other sites More sharing options...
Miles Posted April 4, 2014 Share Posted April 4, 2014 It still sounds like the reaction disk is missing or there is air in the MC or the calipers. Have you bled the MC while it is in the car? Just run plastic tubes from the bleed screws back into the tanks. If you suspect there is still air in the MC you may have to remove it and bench bleed it carefully. See the Brake Forum for many write ups on the bench bleeding set up. In order to completely bleed the 240SX calipers I had to remove the the calipers and hold them so the bleeders were pointed up and move the caliper around using a pressure bleeder and/or someone pushing the brake pedal. Be sure to block the piston with a block of wood so it won't blow out when applying pressure. If the piston blows all the way out you will have a problem. If you adjust the push rod out too far and lock the brakes, open the MC bleeder screws to relieve the pressure and limp home and re-adjust the push rod and re-test until it feels right without locking the brakes. To adjust the push rod, unbolt the MC leaving the lines connected and push it to the side to access the push rod and make small incremental adjustments. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 4, 2014 Author Share Posted April 4, 2014 Yep - it was bench bled when on the car. I don't suspect there is air anywhere. If there were - I would be experiencing some sort of pulling to the left or right - even if a rear wheel, it would still put enough drag on one side to make the car feel funny during stoppage. She stops straight and dead on. I'm leaning heavily toward the reaction disk. Guess I'll know this weekend...thanks for all the help gents! Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 4, 2014 Share Posted April 4, 2014 I don't think that air causes pulling. One of the principles of hydraulics is equal pressure everywhere. The bubble can be on one side, compressing, but the pressure on both sides will be the same. Quote Link to comment Share on other sites More sharing options...
luseboy Posted April 5, 2014 Share Posted April 5, 2014 I would also suspect that if the check valves were still in place they could also be causing problems. I have read conflicting things on whether or not they will work with disc brakes or not, but I know my wilwood master came with them installed on both the front and rear circuits. It's worth a shot to take them out if they're in there just to make sure. Don't remove the cones, they are what seal the brake line to the master, just the black plastic check valves. Quote Link to comment Share on other sites More sharing options...
Nelsonian Posted May 11, 2014 Share Posted May 11, 2014 Would like to know the outcome. Did this ever get sorted out? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted May 12, 2014 Author Share Posted May 12, 2014 Nelsonian - I took apart the old booster and glued the disk to the rod and put it back together. I have not had a chance to swap it back in yet. That is on the docket for this weekend. I'll let you know how it goes. Quote Link to comment Share on other sites More sharing options...
Nelsonian Posted May 12, 2014 Share Posted May 12, 2014 Sounds good. I have a new in box 15/16 mc, but it seems to make more sense in going with the Wilwood 1" mc. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted July 8, 2014 Author Share Posted July 8, 2014 Nelsonian - finally got around to swapping out the booster. It was INDEED the reaction disk. As stated - glued it back to the rod, and readjusted the pushrod since the disk is a few mm thick - and voila! Nice firm pedal now. Sorry for the delay. Quote Link to comment Share on other sites More sharing options...
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