Brake Fluid change

[Deleted member 451]

I have a leaking master cylinder that I'm changing out this weekend and have decided to do a complete change out of the brake fluid. What is the best way to do this? Any cheap tools that make it easier?

 

[RobT]

If you are converting to silicone, then you probably want to rebuild the whole system and replace all the seals. Just went through this on my TR250. If the master cylinder is leaking, likely this is from a build up of moisture in the system, and could well have attacked the slave cylinders & calipers also.

To flush out the pipes, I used Metholated Spirits (Denatured alcohol) and compressed air. I installed stainless steel pistons in the front calipers. You may need a honining tool to smooth the bores on the rear cylinders (and front too if you have drums all-round), although replacement rear masters are pretty cheap. Also check the flex hoses, and replacing these with stainless braided is a good idea too. I used a "mini-vac" pump and a home-made jam jar fluid collector to bleed the system (as I did not have an assistant). Also installed "speed bleeders" on all wheel cylinders (these are replacement bleed nipples with one-way valves built into them to prevent the system sucking back air when bleeding).

https://speedbleeder.zoovy.com/category/automobile_application/


Generally its all fairly straight forward. Of course be careful - its generally advisable to be able to stop!

Rob.

 

[dklawson]

Rob-T, how do you like those "speed bleeders"? I've considered using them but have heard mixed coments. How do they seal the bleed nipple threads to the calliper/cylinder?

 

[RobT]

[ QUOTE ]
Rob-T, how do you like those "speed bleeders"? I've considered using them but have heard mixed coments. How do they seal the bleed nipple threads to the calliper/cylinder?

[/ QUOTE ]

I like them. Especially if you are doing a brake bleed on your own. They come with a coat of sealant of some kind on the threads to avoid air seeping in that way.

Rob.

 

[CraigFL]

[ QUOTE ]
Rob-T, how do you like those "speed bleeders"? I've considered using them but have heard mixed coments. How do they seal the bleed nipple threads to the calliper/cylinder?

[/ QUOTE ]

I use two different kinds... Both are Mityvac. One is a vacuum type bleeder that you hook to the bleed nipple and suck the fluid down from the M/C. This works best for the brake circuit and you don't have to worry about a perfect seal at the nipple because if air is sucked in, it's past the sealed circuit. The pressure bleeder I use mostly for the clutch circuit because reverse bleeding works best there. If I do a complete brake fluid change I do like to use the pressure bleeder from the M/C because it holds a greater volume of fluid and it's quicker. In all three cases, sealing at the nipple usually is not a major concern because of the direction the fluid is moving.

 

[tr8Fan]

I heard once that you could not use DOT 5 fluid on a M/C thats been rebuilt with a brass sleeve. Does anyone know if this is true?

 

[piman]

Hello all,

a point:-

"I used Metholated Spirits (Denatured alcohol)",

methalated spirit is mineral oil based and will damage brake seals so never use it unless you plan to replace the seals.

Alec

 

[dklawson]

CraigFL, the "speed bleeders" are different from the Mity-Vac or EZ-Bleed items.

The Speed-Bleeders are basically bleed nipples with check valves in their stems. You hook up your bleed tubing like normal and back the nipple out a little off its seat. After that you just bleed the brakes by gently pushing and releasing the pedal. The check valve in the nipple prevents the need for a helper or tools like EZ-Bleed. However, my concern was how they sealed the threads between the nipple and caliper/cylinder. If there were no sealant, every time you let the pedal up air would be sucked down the threads and back into the brake system.

I may give them a go next time. I saw that AutoZone or Advance had them with 3/8-24 threads which is what the Mini uses (at least in the front).