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Hello,
This is my second post on this bike, other was about electrical work (Solved), and wanted to ask for assistance on my rear brake. When I press down on the brake, I receive no back pressure, the lines are filled with DOT 3 and I replaced the old liquid in the housing tank. I removed the line connecting to the housing to tank to further reduce where I can find the problem, and I think it is where the pedal meets the housing tank. To me it seems like it is not building up any pressure to push it and activate the brakes. I have attached a photo below of my brake type, but haven't gotten around to removing it completely and taking it apart. I am unsure as to why it wouldn't be functional, and the youtube videos I could find mention air in the lines. Only physical problems that I can see directly is that the rubber where the pedal goes into the master cylinder looks a little worn.
Do let me know your thoughts on this,
Isaiah
I apologize in advance for my wording, I might use the wrong terminology and therefore it might be confusing, ask me in the comments about what I meant in some places and I will draw parts of the photo for you.
Air locked still, MC needs to be flushed and bleed completely before trying to push the rest of the system. Pop the front line, suck out what you can from the mc and put new dot 3 in, thumb over the hole slowly work the pedal, till no air and clean fluid is all you get. Now redo the line and slowly work the pedal a few times cracking the next joint in line, repeat all the way back to the caliper keeping the mc full.
Last edited by TwiZted Biker; Aug 26, 2024 at 02:32 PM.
Sorry...But if I recall correctly...My 77 used Dot 5...I do Not own a Harley that uses other than Dot5
Also..I have Never seen an OE MC chromed...so have No Clue what has been done to Your MC
Last edited by Racepres; Aug 26, 2024 at 02:41 PM.
Either you have a bubble in your system, a stuck brake caliper or you have a master cylinder problem. Judging from the amount of rust you have on your bike, I wouldn't be a bit surprised if a new master cylinder and a caliper rebuild were in order. If there is any pitting inside the caliper bore, you need to replace it. At that point, I would even replace the line to make it all new again. Brake fluid degrades and attracts moisture from the air over time. Moisture over time will cause pitting, and malfunctioning in caliper and master cylinder pistons. On my older bikes, I have found it best to start fresh.
Last edited by SirHarley; Aug 26, 2024 at 02:42 PM.
Hello,
I went ahead and removed the master cylinder (MC) to check the internals and for any physical damage. I cleaned it up to make it more visually appealing and to find breaks/cracks in the body. I disconnected the line to the brake switch and the pedal before removing the MC. As I can tell, it looks to me as if there is a part missing on the pedal connect, as the internal of the MC has a sort of bulbed joint. The rubber boot looks worn away as well, but that is for removing debris, which I can replace at a later date. As for the pressure drop, from inspection (and the photos), it looks like there lacks a seal to pressurize the brakes, but I could be wrong. I have read the prior posts and will work towards narrowing down the steps, but does this MC look damaged?
Inside Master Cylinder Outside of Master Cylinder Pedal connection
If there isn't brake fluid running out of the seal in the MC then it MIGHT be OK, With the bike in the state it is I would rebuild the MC or replace it completely, along with any soft lines....then go watch youtube videos on how to bleed brakes.
Working on rebuilding the MC now, it seems to be stuck in the housing, so working on getting it out and seeing what is damaged and what I need to replace. Given the cost of a new one ($150 when I looked it up), I am going to try and do what I can to repair it and bite the bullet if I cannot.
Working on rebuilding the MC now, it seems to be stuck in the housing, so working on getting it out and seeing what is damaged and what I need to replace. Given the cost of a new one ($150 when I looked it up), I am going to try and do what I can to repair it and bite the bullet if I cannot.
you'll need rebuild kit 41762-58A. I just purchased one a month ago. It came with a new boot and 2 pieces not needed (for drum brakes) I'm pretty sure that DOT 5 is what '77 used.
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Brake with no back pressure, 1977 FLH Shovelhead
