RebekahsZ Posted February 22, 2012 Share Posted February 22, 2012 After my LS2 swap (and other work), I am now having trouble with my hydraulic handbrake progressively locking my rear wheels up after a short drive. The rear footbrakes that use the stock 280zx master cylinder and the 85 Maxima calipers seems to be working fine. Fluid pressure just seems to build in the hydraulic hand brake system until the wheels will almost not turn any more. This system also uses 85 maxima calipers, but uses a willwood master operated by a hand lever. I can release the pressure by loosening either brake bleeder screw on the brake caliper, or by removing the little snap ring that holds the piston in place on the Wilwood master cylinder. However, once I reassemble and rebleed the system and everything seems great, I go for a test drive and in a few miles - the both rear brakes are on again! I'm not even using the hydraulic handbrake! Anybody got any recommendations? I wonder if the master has a bad valve and is somehow pulling fluid from the reservoir and super-pressurizing the system? Should I start with the master cylinder, or the calipers first? Since it is affecting both sides, would it likely be a caliper?? HELP-I want to drive this monster. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 22, 2012 Share Posted February 22, 2012 (edited) The hand brake is not totally releasing so that the pressure can escape to the fluid reservoir (or the rest of the system if that's how it works). If you look you'll see several other threads where people complain that as they drive the brakes come on more and more until they're sitting by the side of the road with smoke coming out of the wheel wells. They have the linkage to the master cylinder adjusted incorrectly. I did the same thing with a clutch years ago. The longer I drove the hotter it got the more it expanded the fluid and the more the clutch slipped until it was undriveable.In your case it sounds like a rear only problem which would indicate that it has to do with the handbrake, not the master cyl. Edited February 22, 2012 by JMortensen Quote Link to comment Share on other sites More sharing options...
beermanpete Posted February 22, 2012 Share Posted February 22, 2012 I agree with Jon. I will add (for clarity) that you need to ensure there is free-play between the brake handle and the master cylinder. Check the adjustment. If the handle is heavy and its own weight is pushing it in the applied direction it might be be self-applying. Add a return spring if necessary to ensure the brake does not self-apply. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted February 22, 2012 Author Share Posted February 22, 2012 (edited) Thanks guys. I'll do a little more searching. I'm on hold for Wilwood tech assistance right now. As you suggest, the handle has fee play and a return spring already. JMortensen, you have described the phenomenon perfectly-I'm gonna study every word that you said-if you have any more suggestions, let me know. It is funny,before I set out on the road this morning, I even shook the handle a little to ensure that I had a little slack in the handle and linkage. I shook it again mid-trip and it was still fine. Even after the system cools, it is like extra fluid is making it into the pressure line from the reservoir. Is it possible that whatever kind of valve regulates entry of fluid from the reservoir, is bad? Just got thru talking to Don at Wilwood tech support. This may be the problem. I changed the actuator rod between my handle and the piston in the master cylinder because the Wilwood and the clevis on my handle were of different thread pitches. It may be that the little ball on the end of the rod is too large and may not be allowing the o-rings to return past the passage that allow the fluid to get back into the reservoir, so with every movement of the handle (like you said, even a rattle) I am adding fluid to the line from the master that cannot get back to the reservoir when not needed. Heat would make it worse as the fluid expands. Gonna go home and look at those actuator rods-that would be a very simple fix (which is what I've been praying for). By the way, Porterfields are very dusty, but they do not fade! Hopefully my rotors aren't warped. Thanks to everybody so very much! I've gone from bumbed to fired up! Edited February 22, 2012 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
Justinp551 Posted February 23, 2012 Share Posted February 23, 2012 I don't know if a residual cable is lurking in there somewhere but I switched to rear disks with a new zx MC and the brakes kept getting tighter each stop. After above said frustrations I happen to find that both outputs of the mc had the residual valves for drum brakes installed. They shouldn't have been there but somehow managed to slip in on assembly/rebuild before I bought it. Just something to check with your set up Quote Link to comment Share on other sites More sharing options...
Justinp551 Posted February 23, 2012 Share Posted February 23, 2012 I don't know if a residual cable is lurking in there somewhere but I switched to rear disks with a new zx MC and the brakes kept getting tighter each stop. After above said frustrations I happen to find that both outputs of the mc had the residual valves for drum brakes installed. They shouldn't have been there but somehow managed to slip in on assembly/rebuild before I bought it. Just something to check with your set up Quote Link to comment Share on other sites More sharing options...
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