jgkurz Posted June 13, 2004 Share Posted June 13, 2004 Hi all, I finally got my car (77 280z coupe) back on the road today after being on jack stands for eight months. One of the upgrades I installed was a new 15/16th master cylinder to compliment my Toyota 4x4 front and 240sx rear caliper upgrade. For some reason I cannot get a firm pedal with a 15/16th master cylinder. I had the same problem on a 78 280z I owned about twelve years ago. The car was stolen before I could figure out the problem. I chalked it up to a bad master cylinder. Seems like I was wrong because my current Z is exhibiting the same phenomenom. I HAVE searched all forums without finding a clue on how to solve this. The general concensus seems to be that bleeding the system properly will solve the problem. I have bled the brakes in this order MC, LR, RR, RF, LF then over again. I honestly believe the system is absent of any air. Evidence of this is the fact that the pedal does NOT build pressure no matter how many times I pump it. The pedal creates some pressure to stop the car but goes to the floor everytime. It will slow the car but will NOT lock the brakes. Has anyone installed a 15/16th master cylinder successfully? I know the advantages of staying with a 7/8th MC, but I'd rather have the larger MC so I can modulate the pedal better. I'm pretty bummed right now. I have spent a fair amount of $$$ on my new brakes and can't use them yet.. Thank you. Quote Link to comment Share on other sites More sharing options...
Synlubes Posted June 13, 2004 Share Posted June 13, 2004 John, Are you getting the same "full flow" at the master and all 4 wheels? I did the 15/16 m/s install with no problems. You said the car sat for a period of time, what about the stock pro valve? Me personally, I would replace the stock unit with an asjustable one. It would give alittle adjustablity for the new brake setup. Much better than stock (IMO). Some here have said something about adjusting the rod for the master, but since I did not have to go that route I`ll let someone who did give some details. Quote Link to comment Share on other sites More sharing options...
jgkurz Posted June 13, 2004 Author Share Posted June 13, 2004 Hi Doug, I have installed a Wilwood proportioning valve, but I ruled it out as part of the problem because I had a similar bad 15/16th experience with my 78z that had the OEM prop valve. What year is your Z? Maybe my 280z uses a different length rod than the 240z or 260z. I do remember playing around with the rod length on my prior 280z. At the time it didn't make any difference. I'll give it a try again if someone thinks that is what the fix is. Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 13, 2004 Share Posted June 13, 2004 Has anyone installed a 15/16th master cylinder successfully? I know the advantages of staying with a 7/8th MC' date=' but I'd rather have the larger MC so I can modulate the pedal better. I'm pretty bummed right now. I have spent a fair amount of $$$ on my new brakes and can't use them yet.. Thank you.[/quote'] Hi John... I haven't used the larger MC, but I doubt that this is where your problem lies. All else equal, the larger MC should have less travel for a given brake pressure (i.e., firmer). You mentioned having done the Toyota front caliper upgrade. Since those are 4 pistons calipers, did you bleed both sides of each caliper (I'm assuming they have bleeders on both sides). Do the outside half first, then the inside half, in the same order that you were already using. I'm curious why the larger MC would be easier to modulate - seems like the extra travel of the smaller MC would make modulation easier. Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted June 13, 2004 Share Posted June 13, 2004 You mentioned having done the Toyota front caliper upgrade. Since those are 4 pistons calipers, did you bleed both sides of each caliper (I'm assuming they have bleeders on both sides). Do the outside half first, then the inside half, in the same order that you were already using. ???? ... even though there are mutiple pistons there is still only one bleeder per caliper. Have you checked the length of the pushrod? It is a strong possability that it needs to be adjusted outward to fully engage the master cylinder. I have not done the 15/16 upgrade but do you know if the pushrods are the same length? Quote Link to comment Share on other sites More sharing options...
jgkurz Posted June 13, 2004 Author Share Posted June 13, 2004 Tim, the Toyota 4x4 vented calipers only have one bleed point. I believe it covers both sides of the caliper. As I understand it, with a larger master cylinder it requires more effort to get the same amount of clamp to the pads. The 7/8 MC will have a more sensitive feel, but is more difficult modulate or between slight and hard braking. I think it boils down to personal preference. The only idea I can come up with is that maybe I need the vacuum booster and rod assembly from a 1980 280zx. That's the car my 15/16th MC is for. My pedal is bad with the car on or off so it might be a problem with the rod not the vacuum booster. I don't know how it could the rod, but that all I can guess. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 13, 2004 Share Posted June 13, 2004 i did the install no problem but then again i used the matching brake booster as well. did you check to make sure the master cylinder was working properly prior to installing fluid and lines? Honestly sounds like there is a hole in your brake booster or your arn't geting any vacumn... maybe check the vacumn lines, also do you have a vacumn bottle installed? -Ed Quote Link to comment Share on other sites More sharing options...
CruxGNZ Posted June 13, 2004 Share Posted June 13, 2004 I did the 15/16" master cylinder swap a few years back. I had similar symptoms with my brakes, turned out to just need the rod adjusted and I got a nice firm pedal. I bled my brakes so many times thinking there was air in the lines . Oh well. !M! Quote Link to comment Share on other sites More sharing options...
jgkurz Posted June 13, 2004 Author Share Posted June 13, 2004 Ed, I'm encouraged by the fact that you were successful with your upgrade. I'm starting to think I need the matching booster assembly. Did you use a booster and rod from a 280ZX? My brakes with the 7/8th MC worked fine prior to performing the upgrade. The pedal was firm and the booster did not leak. The vacuum bottle had all the vacuum lines intact and none were leaking. Quote Link to comment Share on other sites More sharing options...
jgkurz Posted June 13, 2004 Author Share Posted June 13, 2004 I did the 15/16" master cylinder swap a few years back. I had similar symptoms with my brakes' date=' turned out to just need the rod adjusted and I got a nice firm pedal. I bled my brakes so many times thinking there was air in the lines . Oh well. !M![/quote'] MatGNZ, What year car do you have? Were you able to simply adjust your original rod or did you have to put in a new one? Thanks! Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted June 13, 2004 Share Posted June 13, 2004 You need to bleed the master cylinder. Until you get all of the air out of the master cylinder you will not get any pedal pressure, and you will not be able to bleed the rest of the system. Get a bleeding kit from an autoparts store that comes with the plastic cup and some clear tubing. Fill the reservoirs. Attach the clear plastic tube to the rear bleeder on the side of the master cylinder, and put the open end into the rear reservoir. SLOWLY, stroke the piston of the master cylinder through its entire range (its usually better to do this on the bench where you can verify full stroke). Repeat until no air bubbles appear in the tube. Close the rear bleeder and repeat the procedure for the front. After the master cylinder is fully bled, bleed the res of the system starting at farthest wheel and working towards the closest. Have fun Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted June 13, 2004 Share Posted June 13, 2004 One other silly suggestion. Verify that the bleeder screws on your new calipers are mounted so that the bleeder is point up (not down). I have heard of people putting the calipers on the wrong side and getting the orientation of the bleeders incorrect. You can bleed them as many times as you like and not get the air out if the bleeder is not on top. Quote Link to comment Share on other sites More sharing options...
rags Posted June 13, 2004 Share Posted June 13, 2004 It's going to be a pain in the @ss but it is pretty simple to see if you have a rod lengh issue. What I did was to look at the piston end of both M/C's. Obviously you have to remove them. What I found is that the indent that the rod pushes on in the M/C is much deeper on the 13/15" M/C requiring a longer pushrod. I swapped mine for the ZX rod and still needed to adjust it longer to get a nice pedal. Worth a shot. Joe Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 13, 2004 Share Posted June 13, 2004 I've got similar problem going on with my brakes too. I had a line go in the rear, and I lost all the fluid in the rear system. I've since replaced the line, and bled the MC, and the entire system at least 4 times, and I still have a soft pedal. It goes to the floor. Even softer with the engine running. Before the brake hose let go the brakes were working awesome. I have 240SX rear, Wilwood front, with a 7/8 MC, and 240Z booster. I bought a new booster and MC, but after reading this thread, I must still have air in the system. Maybe it's worth pulling the MC and bleeding it out of the car so I know I'm getting a full stroke. Pete Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted June 13, 2004 Share Posted June 13, 2004 I did the upgrade probably 14 years ago now on my 1970. I had to adjust the rod to get the brakes to engage properly. It should be simple to tell. If the rod is too short the brake pedal will move without any backpressure. When I first did it I got 2 or 3 inches of pedal movement before the brakes came in with the last inch of travel. Adjusting the rod was simple on a 240. The rod is threaded and adjustable. I adjusted it out a couple of times until I got maybe 1/2 inch of free travel before backpressure. I did it with the stock 1970 booster ( the really small one). Two other things. I had to swap the brake lines front to back on my 240. Make sure the front brake line goes to the end of the MC with the larger reserviour. Might already be that way with a 77. Second I upgraded to stainless steel brake lines. Makes a huge difference in pedal feel. Now once the pedal engages the MC, the brakes come on right now with very little additional pedal travel. Quote Link to comment Share on other sites More sharing options...
srgunz Posted June 13, 2004 Share Posted June 13, 2004 Before you make any arbitrary rod adjustments. Measure both m/cyl. Measure from end of cyl. to the two bolt flange. Next with a dial calipers using the depth measurement end, measure from end of ctl. body to the piston in side the cyl. If both cyls. are the same it is not the rod length. As far as bleeding, once you do the m/cyl. itself you can bleed the front end first or back first if you want. The systems are seperate and it makes no difference. Quote Link to comment Share on other sites More sharing options...
CruxGNZ Posted June 13, 2004 Share Posted June 13, 2004 MatGNZ' date=' What year car do you have? Were you able to simply adjust your original rod or did you have to put in a new one? Thanks![/quote'] I have a '73 and kept the booster and rod from the '73. All I changed was the master cylinder. !M! Quote Link to comment Share on other sites More sharing options...
fastzcars Posted June 13, 2004 Share Posted June 13, 2004 I had air line my lines, and no matter how many times (6 times) that I tried to bleed my brakes, the peddle would go to the floor. I finally bought a great product called MOTIVE PRODUCT power bleeder. It's a 4 quart bottle with a hand pump in the top. You fill the bottle with brake fluid, mount the brake adapter to the master cylinder,pump the handle to 10 to 15 lbs. and bleed all four caliper's in 20 minutes. I highly recommend the product. I was fooling around with my brakes for 2 weeks straight before I finally bought the power bleeder. Made it so easy. THey advertisein the GRASSROOTS MOTORSPORTS magazine. I can relate JGkurz. Good luck. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted June 13, 2004 Share Posted June 13, 2004 I used the booster and master cylinder brand new from a ZX... the rod (i'm assuming your talking about the rod taht goes to the brake pedal i just adjusted. This is probably all you need to do. i adjusted mine prior to filling and everything and i had pressure with the car off. (ie.. pump the brakes till they get hard) Let me know how it goes and if you need a pic... -Ed Quote Link to comment Share on other sites More sharing options...
jgkurz Posted June 15, 2004 Author Share Posted June 15, 2004 Hello everyone, I have an update on my brake situation. I went ahead and adjusted the rod out several turns. There was no improvemnt. It simply bottomed out the piston in the master cylinder. Funny how a pedal gets real hard when you hit the end of the M/C. For whatever reason the M/C just won't build pressure. For the life of me I can't figure out why the 7/8 M/C works fine and 15/16 won't get a solid pedal. At this point I think I'm going to try the Power Bleeder. I'd like one I could use on any car. Motive Products offers several types including a universal model and an import model. Does anyone know if the universal will fit a Nissan/Datsun? http://www.motiveproducts.com/02bleeders.html Thanks Quote Link to comment Share on other sites More sharing options...
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