Mixing different brake fluids

[dschmitta]

hey everyone,

Was having problem with rear brake light staying on. Before adjusting lever, I TOOK OFF rear resevoir cover and it was empty. I don't know what kind(DOT 3/ synthetic DOT 5) was used in bike, and had heard that you should not mix different kinds? Is this true? I have both DOT3 and synthetic DOT 5, but unsure which to use. Is there any way to tell? Any help greatly appreciated. Dave


P.S. Having trouble finding sweet spot for rear brake pedal. The light either stays on constant or wont work at all when using pedal. Would low fluid level be doing this? Thanks

[DGXSER]

First of all, you do NOT want to mix DOT 3 with DOT 5. It will make this goo type gelatin that looks like crumbled up eraser. DOT 5 is purple in color typically so you should be bale to look at what has been dripping or what little comes out of the MC or caliper. DOT 3 and 4 interchange fine.

Fluid level will have no effect on brake light. The light is simply a push button type switch on a spring. Spring attaches to the brake pedal. When the pedal goes down it pulls on the psring and pulls the switch into contact. When the brake pedal goes back up (which is accomplished by the large spiral spring not the MC) the spring is released and the switch opens turning the light off.

[CaptonZap]

Take the switch off, and inspect it. It is down where a lot of dirt can get to it, and we all know that dirt is the enemy of mechanical devices. I have an 80G, and the following describes it, and I don't know if they are all the same, but the same principles apply.
There are two nuts on it, which are used to adjust it relative to the spring. The travel of the plunger is not much, 1/16 in, approximately, the spring takes up the added travel of the arm.
Take the switch off, and clean the external housing. Hook the hole in the plunger with a piece of wire, and pull on it. Does it move out? When you release the pressure, does it return all the way? If not, soak it in solvent and work the plunger. It should loosen up and work right. If it pulls out, but does not go back in, there may still be some gunk in it, keep soaking and working the plunger. Some compressed air blown in the plunger end may help, or worsen thing, depending on what is causing the binding. Use discretion. If the plunger moves freely, and it does not retract, the internal spring is probably shot, and a new switch is in order.
Now, take a continuity tester of your choice, and test the switch by checking continuity between the two terminals when the plunger is pulled out. If you get continuity when you pull the plunger, you're golden. Put it back on, and adjust the two plastic nuts until the spring pulls the plunger down when the pedal is depressed, and the internal spring pulls it back up when the pedal is released.
If you don't get continuity, again, a new switch is in your future.
Good luck, and let us know what you find. CZ

[dschmitta]

Take the switch off, and inspect it. It is down where a lot of dirt can get to it, and we all know that dirt is the enemy of mechanical devices. I have an 80G, and the following describes it, and I don't know if they are all the same, but the same principles apply.
There are two nuts on it, which are used to adjust it relative to the spring. The travel of the plunger is not much, 1/16 in, approximately, the spring takes up the added travel of the arm.
Take the switch off, and clean the external housing. Hook the hole in the plunger with a piece of wire, and pull on it. Does it move out? When you release the pressure, does it return all the way? If not, soak it in solvent and work the plunger. It should loosen up and work right. If it pulls out, but does not go back in, there may still be some gunk in it, keep soaking and working the plunger. Some compressed air blown in the plunger end may help, or worsen thing, depending on what is causing the binding. Use discretion. If the plunger moves freely, and it does not retract, the internal spring is probably shot, and a new switch is in order.
Now, take a continuity tester of your choice, and test the switch by checking continuity between the two terminals when the plunger is pulled out. If you get continuity when you pull the plunger, you're golden. Put it back on, and adjust the two plastic nuts until the spring pulls the plunger down when the pedal is depressed, and the internal spring pulls it back up when the pedal is released.
If you don't get continuity, again, a new switch is in your future.
Good luck, and let us know what you find. CZ

Thanks for help. I'll clean, check contin. and adjust tomorrow and let ya know the results. Thanks

[Shacknasty]

As to the color of the different brake fluids, DOT5 is purple when it is new. After a while of use, moisture and crud will contaminate it and the fluid looks a brownish amber...just like the other fluids.

To be safe, you should clean your entire system thoroughly with brake cleaner or alcohol, from caliper to hose to master cylinder and refill. I use DOT3 as recommended.

[dschmitta]

still having trouble

Hey everyone. Might sound real stupid, but I tried to take off the switch and I can't make it happen. I adjusted it all the way up and down, can't get the switch assembly out of the bike. I adjusted the pedal height as high as can go, but it will dip just a hair and trigger light and can't figure out how to keep it up. Wondering if bad spring? Any help greatly appreciated.

[DGXSER]

Just went through this yesterday. There are three things to adjust on the rear brake. The pedal height, the master cylinder push rod, and the brake light indicator.

First thing I did was raise the brake light switch all the way up as high as it could go, basically on all the time now. Then I loosened the rod that pushes on the master cylinder, plenty of space in there now. And loosen the pdeal height screw as well.

Now, I used the pedal height adjuster to just start to preload the return spring.

Next raise the push rod for the MC so it is very close to touching but a little more clearance than you want/need. Then fine tune the pedal height adjustment so you get that 1/8" or so of pedal travel before the rod hits the MC plunger.

Now with the bike turned on you will see your rear bake light is on. Turn the threaded coupling lowering the brake light switch to just a little past when the brake light goes off. Try the pdal a few times to see that the brake light comes on and goes off when you want it to. May take a few subtle changes to the brake light switch height to get it where you want it, but that should do it.