Question about replacing brake lines

[alexwolf1216]

Tonight I removed my calipers and rotors in order to tackle the brake lines. I read to NOT let all of the brake fluid drain, so I used latex gloves and zipties to stop the flow from the hard lines removed from the caliper. My question is, when I remove the soft lines to replace, it looks like I will lose fluid faster. Do I block up the hard line to the master cylinder the same way and hope I dont lose it all? I am afraid that it may take me a little while to get the lines replaced and re-installed. Rookie question, but why is it so important to not re-bleed the master cylinder? Is it just time consuming or is it difficult?

I have to wait for some parts, so I cant start reassembly just yet.

Alex

[DMCMW Dave]

Let it drain. You want the old fluid gone. The recommendation was probably a time saver. The other common recommendation to not rebelled the master is to avoid flooring a used one in the bleeding process. That one is new.

[alexwolf1216]

OK great. So I will let it drain out, replace lines etc, then refill at the master? Is there anything else I need to do or just start pumping brakes and bleeding as normal?

[David T]

OK great. So I will let it drain out, replace lines etc, then refill at the master? Is there anything else I need to do or just start pumping brakes and bleeding as normal?

The biggest problem with letting all of the fluid drain out is that once the reservoir empties you will have to rebleed the master cylinder and to do that may require removing it and bleeding it on the bench. If the fluid is dark and thick the chances are great that the inside of the master cylinder is corroded. Especially if you are replacing leaky calipers. When you bleed the system you will be pushing the pedal all the way down forcing the seals inside into the corroded areas where they will get torn up and start leaking. If you are replacing leaky calipers the best advice is to replace all of the calipers (or rebuild them) replace all four hoses, and replace the master cylinder all at the same time. Then it is on to the clutch!

[alexwolf1216]

The master was just replaced prior to shipping at DMCMW. Its brand new. Do I still need to take it out? The fluid that is leaking is clear, brand new, based upon what I was billed for by Dave :)

Alex

[David T]

The master was just replaced prior to shipping at DMCMW. Its brand new. Do I still need to take it out? The fluid that is leaking is clear, brand new, based upon what I was billed for by Dave :)

Alex

In that case you should not have to replace the master cylinder but if it empties it may need to be rebled. I would try capping the lines anyway, keeps things less messy too.

[alexwolf1216]

So, I should try to cap on the inside of the hard line before the tab while I fight with the flex lines through the frame? Then just keep the MC topped off teh best I can to not let it run dry?

[David T]

So, I should try to cap on the inside of the hard line before the tab while I fight with the flex lines through the frame? Then just keep the MC topped off teh best I can to not let it run dry?

Or you just disconnect the two hard lines at the master cylinder and plug the outputs of the master to keep the fluid in. That way once the stuff in the lines stops coming out you don't have to worry about emptying the master cylinder.

[alexwolf1216]

Good thought. Last question since I am at work and cant go look now......cap from the top via the panel or from underneath? Is there something easier than zip ties and silicone gloves?


Alex

[David T]

Good thought. Last question since I am at work and cant go look now......cap from the top via the panel or from underneath? Is there something easier than zip ties and silicone gloves?


Alex

When working on things with fluids it is always better to work from above. That way it doesn't drip all over you. Buy a cheap assortment of plastic caps to stick in the hole to plug it up. Any time you disconnect a brake line you should cap both ends. Keeps the dirt out.