Master Brake Cylinder

[onionfmr]

Okay, I didn't get any replies to my tire question. So, I'll try another question. Rear wheel on my '70 FLH Harley is locked. Bike has 7,700 original miles and obviously sat for years. I'm guessing that the DOT 3 brake fluid over time has done in the master cylinder and wheel cylinder. I have been able to locate what appears to be a correct Wagner master cylinder and a Accel wheel cylinder. I have also located another Wagner look a like master cylinder that is for DOT 5 fluid. Considering how DOT 3 brake fluid likes to absorb condensation and how it can give that "special" touch to your paint. I'm thinking of going the DOT 5 route. One local collector has recommended to replace instead of rebuild both cylinders and go with DOT 5. I plan to ride the bike around 1,000 miles a year and may take it for AMCA judging. Looking for some additional opinions on what's the best way to go on the brakes? Thanks in advance - Ted.

[charlie frey]

I wouldn't replace an original part with an aftermarket one unless it was totally necessary.
I've had great success cleaning old master and wheel cylinders with ball hones and/or emery paper and installing inexpensive and readily available rebuild kits.
My '64 FLH is original and has, in its life, sat for extended periods, and it still has the original brake components.
As for the paint removing properties of DOT 3...that rear master cylinder is pretty far from your sheetmetal.

[Kojack]

I've rebuilt my brake parts a few times, just like Charlie says. The last time I switched to DOT 5 fluid. So far so good. DOT 3 does tend to absorb water which causes corrosion problems. In my case I was rebuilding either the master cylinder or caliper every spring. The DOT 5 is supposed to prevent this, I'll let you know. If you rebuild your parts, just make sure to wash the DOT 3 out of everything including the lines, with denatured alcohol. Then you can just fill the system with DOT 5. You can't mix the DOT 3 and DOT 5. Makes everything gummy if you do.

[Jack K]

Right at two years ago I had to go thru the rear brakes on my 66 FL. The master cylinder was OK after a little emery paper but the wheel cylinder had one of the pistons seized to the cylinder. It was toast. I used a new Accel wheel cylinder. It fit perfectly. I put a kit in the master cylinder, replaced the flex line to the rear cylinder and squirted alcohol in the steel line and blew it out with compressed air. Even thou the instructions for both the master cylinder kit and the wheel cylinder assy said to use DOT 3, I used DOT 5. As I said when I started, about two years now and the brakes are working just fine. I hope this reply works like its supposed to.... this is the first time I've ever done this.

[onionfmr]

Thanks to all for your information and advice. I've been restoring old cars for years and this is my first attempt at a Harley. Looking forward to getting started on this one. I have a ton of questions, which I will be posting and appreciate any advice, information and help. Thanks again - Ted.

[Paquette]

If you look at the owners and factory manuals, DOT 5 is always specified----M

[portagepan]

Master cylinder.

You might want to double check on that W/L master cylinder. I think they make two different ones that look alike. One is a little different inside, for the return on the '73 on rear disc.

[swall]

The DOT 5 designation did not even exist before 1974. If earlier Harley's used silicone fluid, it would have been a manufacturer's brand and not covered by a DOT designation or SAE spec.

[VPH-D]

The master cylinder bodies were the same between drum and disc brakes. However, if you bought one or the other, you had to specify usage. The drum master had a -58 part number, and the disc used a -72 IIRC. The rebuild kit worked for either application, as it included the residual pressure valve needed for one kind of brakes[I can't remember which at the moment]. The rubber parts suitable for DOT 5 were identified by a yellow and white stripe.
VPH-D

[onionfmr]

I'm still a little concerned about getting my brake system clean of DOT 3 fluid before adding the DOT 5. Spoke with a local Harley guru yesterday. He recommended using a DOT 5 brake fluid product called Cartel silicone brake fluid. Says it is compatiable with DOT 3 brake fluid. I've checked out Cartel's web-site and that is what they state. He says he has been using it for years with no problems. Just flush the existing system with it, fill and bleed. This would be way too easy!!! Any comments on this one? Thanks in advance - Ted.

[Kozy]

I believe all DOT 5 fluid is silicone. I've been using the local auto supply store's brand. I have a '75 FLH that's run DOT 5 for several years. I just pumped out the Dot 3 and flushed Dot 5 through and filled just as Onionfmr describes. I also tried a Lockheed Wagner master cylinder with Dot 5 and it wouldn't pump it. The rear cylinder on the bike is after market and works fine. My front cyl. is stock but has been rebuilt several times. It pumps DOT 5 just fine but the aftermarket seals may be what makes it work.(differant material than stock) If you experience a front master cylinder leak ith DOT 3 your front fender will tell you why you want DOT 5. (don't ask me how I know) That residual pressure valve is for the drums. Installed on a disc system fluid pressure on the caliper is not released after applying the brake and the brake will eventually lock up after several applications. Once again don't ask!

[Kozy]

I believe all DOT 5 fluid is silicone. I've been using the local auto supply store's brand. I have a '75 FLH that's run DOT 5 for several years. I just pumped out the Dot 3 and flushed Dot 5 through and filled just as Onionfmr describes. I also tried a Lockheed Wagner master cylinder with Dot 5 and it wouldn't pump it. The rear cylinder on the bike is after market and works fine. My front cyl. is stock but has been rebuilt several times. It pumps DOT 5 just fine but the aftermarket seals may be what makes it work.(differant material than stock) If you experience a front master cylinder leak ith DOT 3 your front fender will tell you why you want DOT 5. (don't ask me how I know) That residual pressure valve is for the drums. Installed on a disc system fluid pressure on the caliper is not released after applying the brake and the brake will eventually lock up after several applications. Once again don't ask!

[Kojack]

Hmmm, your first post indicated that you plan on replacing or rebuilding everything so I'm not sure what you're concerned about. Just changing to silicon fluid won't repair your wheel cylinder and master cylinder. I did a little internet searching and found a good article on changing over. http://www.xs11.com/tips/maintenance/maint1.shtml
By the way, this article points out that you shouldn't use any solvents on the rubber parts, which is true. In my earlier post I mentioned using denatured alcohol to clean the parts. This is fine for metal parts. I did use it on my hose also but blew it out with air when I was done. I feel the alcohol dries too quickly this way to do any damage to the hose but mine had a cut in the outside so I ended up replacing it later that month anyway.

[onionfmr]

I wasn't clear in my earlier post. When I said existing system, I meant old brake lines with new master cylinder and wheel cylinder. I didn't think that adding and flushing with the Cartel brake fluid will fix my problem. Won't be doing much pumping of the master cylinder since the brake pedal won't move. I am going to replace the master cylinder and wheel cylinder. I would like to reuse the original brake lines, if possible. My concern is that the brake lines get cleaned out to avoid any compatibility issues between DOT 3 & DOT 5 brake fluids and not compromise the integrity of the brake lines as part of the cleaning process. Don't want left over old DOT 3 brake fluid contaminating my fresh brake system. Just seemed way too easy to install new master cylinder, add the Cartel DOT 5 brake fluid to the master cylinder and then flush the brake lines using the Cartel DOT 5 brake fluid. No worry of contamination. Then install new wheel cylinder, connect brake line and then bleed the system.

[Kojack]

According to the article, the old sludge is what causes the gum problem. The fluids themselves are compatible. Take the old lines off and give them a good close examination. If they look OK blow them out with air and reuse them. If you do that you should be able to use any silicon fluid. If your old hoses are iffy, get new ones. I was able to get new original hoses for my '76 from Harley this past summer and they weren't that expensive.