rand Posted April 13, 2020 Share Posted April 13, 2020 I'm trying my hand at bleeding brakes for the first time on my '71 240Z that I got from my father-in-law and am having some trouble. After pulling a bunch of components* off and cleaning them out, I can finally get a good stream of fluid out of the bleeders with no bubbles using the old glass jar method. The problem is that when I close off the bleeders and press on the brake pedal the wheel cylinders don't budge at all. I would expect to be able to see them actuate at least a little bit even with no vacuum on the booster (the engine isn't installed yet). Is that a reasonable expectation? Anything else I can do to debug this? I'm really hoping the wheel cylinders aren't shot, as they're the early models and are crazy expensive these days. Is there any easy way to tell if these are the problem? * These are the components I've pulled off so far. I've blown compressed air through everything to make sure there are no blockages. "Pressure Regulating Valve" (#1 in the Haynes manual) - the seal had some gunk in it, but otherwise was in good shape The Y splitter next to the pressure regulating valve - pretty clean The soft lines going to the drums - one of these had a huge wad of gummed up fluid stuck in it that shot out like a rocket The hard lines connecting the soft lines to the cylinders - totally clean The wheel cylinders - these were filled with gummy brake fluid, but once I cleaned that out they seemed to be in good shape as far as I could tell. One of them was missing a spring, so I'll need to find a replacement. Thanks! Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 13, 2020 Share Posted April 13, 2020 12 hours ago, rand said: The problem is that when I close off the bleeders and press on the brake pedal the wheel cylinders don't budge at all. The wheel cylinders - these were filled with gummy brake fluid, but once I cleaned that out they seemed to be in good shape as far as I could tell. One of them was missing a spring, so I'll need to find a replacement. Does the brake pedal move? Does it drop to the floor or does it stay high and firm? What does "cleaned out" mean? Did you disassemble them? They're easy to take apart. Pull the pistons out, if you can. Odds are that they're rusted in place. Quote Link to comment Share on other sites More sharing options...
rand Posted April 13, 2020 Author Share Posted April 13, 2020 2 hours ago, NewZed said: Does the brake pedal move? The pedal moves a significant amount when I press on it, even with the bleeders closed. I haven't observed any fluid leaking out since I reassembled everything. 2 hours ago, NewZed said: What does "cleaned out" mean? Did you disassemble them? I totally disassembled the cylinders, and other than being filled with gummy fluid they were in good shape. I cleaned out the cylinders and was able to easily push the pistons in and out freely. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 13, 2020 Share Posted April 13, 2020 39 minutes ago, rand said: The pedal moves a significant amount when I press on it, even with the bleeders closed. I haven't observed any fluid leaking out since I reassembled everything. I totally disassembled the cylinders, and other than being filled with gummy fluid they were in good shape. I cleaned out the cylinders and was able to easily push the pistons in and out freely. Bleed the front brakes. They can have a big bubble that will take up most of the MC movement. Have you tried pumping the brake pedal? That will compress any air bubbles and create more pressure. If you can get the wheel cylinder to work by pumping that means you have trapped air in the system. And, the MC might have a blown seal. It will push fluid with no back pressure but not when it has to work. There are three seals in the MC, one each to make pressure and another to stop leaks. So, sometimes you can't really tell when the MC is bad. Quote Link to comment Share on other sites More sharing options...
rand Posted April 13, 2020 Author Share Posted April 13, 2020 Got it - I just ordered myself two wheel cylinder and one master cylinder rebuild kits. Hopefully I can rebuild them all this weekend with new seals, and I'll report back. Does anyone have a preferred how-to video for rebuilding? Quote Link to comment Share on other sites More sharing options...
rand Posted April 21, 2020 Author Share Posted April 21, 2020 (edited) Great news! I rebuild the wheel cylinders and (partially) rebuilt the master this weekend, and things seem to be working. Unfortunately the master cylinder rebuild kit I got was only for the 70-72 Nabco and I have a Tokico. The only parts that seem to fit from the kit were the rubber rings that hold in the check valves. It seems like the issue was the wheel cylinders all along, but I ordered myself another master rebuild kit from classicgarage.com, so I'll see if that one works out at some point. My last question is do I need to do anything special to adjust the rear brakes once I have the drums on? I cranked the adjustment wheel out until I could barely get the drum on, but is there any further adjustment necessary? I read that they're "self-adjusting" but does that apply only to the handbrake? Here's some quick triumphant videos: Rear cylinder actuating Basic brake functionality confirmed Edited April 21, 2020 by rand Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.