WizardBlack Posted August 23, 2007 Share Posted August 23, 2007 OK, long story short; bought the car, brakes need pumped several times to get decent pressure. I tear the car apart and install master bushing kit, struts, springs, new pads and rotors in the front and stainless braided brake lines. I also replace one or two small hard lines that had rounded off heads by previous owner. We bleed the brakes (left rear, right rear, right front, left front). It feels a tad better, but still takes a small amount of pump to get the brakes HARD like stainless lines should be. This is while the car is up on stands still. I chalk it up to a 30 year old car. I test drive it and the brakes go to the FLOOR. I need to pump them 5 full strokes to get back to where they were before with a few. I was in the cockpit at the pedal and my buddy did the bleeding. He's done 'em before so I thought perhaps something else is at issue. Could it be the checkvalve? Need to bleed the master cylinder? MC just plain bad? Also, sanity check: The bleeder screw is oriented at the TOP of the caliper when it is installed, yes? NOT the bottom? TIA, Mark Quote Link to comment Share on other sites More sharing options...
240playtoy Posted August 23, 2007 Share Posted August 23, 2007 Common problems include reaction disks. Replaced master cylinders can sometimes have different depths in the plunger, making your booster move before actuating the master cylinder. Here's some literature for you, I believe both problems are mentioned in it. http://forums.hybridz.org/showthread.php?t=113240&highlight=reaction+disk Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted August 23, 2007 Author Share Posted August 23, 2007 Common problems include reaction disks. Replaced master cylinders can sometimes have different depths in the plunger, making your booster move before actuating the master cylinder. Here's some literature for you, I believe both problems are mentioned in it. http://forums.hybridz.org/showthread.php?t=113240&highlight=reaction+disk Hmm, I noticed that there are two stages of resistance on the brake pedal. I scanned through every post in that thread and the one they link to from there and I didn't really see that anyone actually derived a solution to the problem. They saw the RD fell out and put it back in and even super glued it. One fellow adjusted his rod back and forth and could still never fix it. What did you end up doing and did you get actually quick responding and 'stiff' brakes like you should with stainless brake lines? Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted August 30, 2007 Author Share Posted August 30, 2007 Update: Methinks the master cylinder was shot so I replaced it and carefully bled the new one. Things seemed to be looking better, but still not great. I bled the rears first (put speedbleeders on while I was at it) and it didn't get much firmer. I could pump once or twice on the right front bleeding and then the pedal got much softer and I heard a clunk/pop. Couldn't I.D. the sound so I kept on going. I continued to try to bleed but it was soft. I switched to the other side and it would be hard for one pump of the brake pedal and then soft again until I leave it alone for several minutes. We tinkered with the booster check valve and couldn't get it to work better. Finally, my friend actually plugged the nipple off on the booster with his finger and the brakes are now hard! So we figured the check valve was in wrong. We referenced the haynes manual. It shows that the metal check valve should have the center body showing the flat side toward the engine and the chamfered side towards the booster. We flipped it around and the pedal stayed hard. We finished bleeding and when for a test drive. I have absolutely NO booster effect at all, BUT the brakes are nice and hard now. I dunno. There are two sections of the booster with a check valve between them and one between the rear section and the outside. I think there are some leaks in one of the checkvalves or the diaphragm or both, so I ordered a replacement from Autozone for $115. I can drive it now, but I will develop a He-Man left leg in short order. I guess we'll see if the booster replacement fixes it... On a side note, I priced the upgrade to S12+8 four piston calipers up front and new pads to go with them and it's only about $100 after core refunds! Too bad the 240SX rear conversion is about $300 plus the cost of the Maxima brackets. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted September 1, 2007 Author Share Posted September 1, 2007 Another update: I have the new booster on. I used a set of vernier calipers to measure the pin pushing on the MC and adjusted it to the same length as the original. I also did the linkage on the inside to make sure I had no problems. The car still has a very stiff pedal with hardly any movement. Maybe 1" total. However, it still is a very very high effort pedal. Just like it had no booster at all. Help! Quote Link to comment Share on other sites More sharing options...
nbesheer Posted September 1, 2007 Share Posted September 1, 2007 Update: Methinks the master cylinder was shotWe tinkered with the booster check valve and couldn't get it to work better. Finally, my friend actually plugged the nipple off on the booster with his finger and the brakes are now hard! So we figured the check valve was in wrong. We referenced the haynes manual. It shows that the metal check valve should have the center body showing the flat side toward the engine and the chamfered side towards the booster. We flipped it around and the pedal stayed hard. We finished bleeding and when for a test drive. I have absolutely NO booster effect at all, BUT the brakes are nice and hard now. I dunno. There are two sections of the booster with a check valve between them and one between the rear section and the outside. I think there are some leaks in one of the checkvalves or the diaphragm or both, so I ordered a replacement from Autozone for $115. I can drive it now, but I will develop a He-Man left leg in short order. I guess we'll see if the booster replacement fixes it... On a side note, I priced the upgrade to S12+8 four piston calipers up front and new pads to go with them and it's only about $100 after core refunds! Too bad the 240SX rear conversion is about $300 plus the cost of the Maxima brackets. You brake with your left foot ? or was that a typo ? Quote Link to comment Share on other sites More sharing options...
auxilary Posted September 1, 2007 Share Posted September 1, 2007 left foot braking is common in racing, because you can maintain throttle and braking at the same time Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted September 1, 2007 Author Share Posted September 1, 2007 You brake with your left foot ? or was that a typo ? Oops, yeah. Sorry, I use the right foot unless it's auto, then I use the left foot. Hey! If everyone is reading things so close, what's your solution to the problem? Quote Link to comment Share on other sites More sharing options...
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