When swapping my front master cylinder is it necessary to completely bleed the line if I am just going to unhook the brake line from the old master cylinder and put in on the new one?&nbsp\\; Also, I have the same bottle of DOT 4 brake fluid I used two years ago when I added the new brake line, is it still good or should I buy a new bottle?&nbsp\\;

 

As long as the bottle is sealed tight, I don't see a problem. If the cap wasn't sealed properly, brake fluid could be contaminated.
This is how I look at it, if it is going to cost $10, I will get a new bottle, know what I mean?

 

I would say yes to both questions.&nbsp\\;\\\\\\; Anytime you disconnect the brake lines you will get air in the system and bleeding is necessary to remove the air. I would get a new bottle of brake fluid if the seal is broken.

 

if you have trouble bleeding brakes you can take a pump type oil can that is clean inside fill it with brake fliud,attach a rubber hose to oil can.then open bleeder in caliper and push clean brake fliud up into the master cyl.this will push the air out of the line.i would also get a new bottle of fliud

 

I dont think i would do the pump method with dot 4. if any is left in your line and it sprays it can get on your paint. dot 4 will eat your paint. I would change to dot 5 works fine and wont hurt your paint. just flush system and fil with dot 5.

 

Mighty vac......$29.00 at auto zone. I switched to Dot 5 also....Good luck.

 

Or this (see picture)
Pain in the S to manual bleed the brake

 

thanks guys, I was leaning towards getting a new bottle anyway, it's cheap insurance and peace of mind.&nbsp\\; Changing to DOT 5 won't damage the seals or anything in my calipers?
&nbsp\\;
What about DOT 4 residue in the line mixing with the DOT 5?&nbsp\\;
&nbsp\\;
Thanks for the reccomendations on the tools, I will look into that.&nbsp\\; I'm sure this won't be the last time I bleed the brakes.&nbsp\\; I know&nbsp\\;I will be swapping out my rear brake line for a SS braided one and I will eventually go to 16" apes which will require changing front brake lines again, plus I can add another tool to the box.&nbsp\\;

 

I'm picking up the mighty vac today.&nbsp\\; thanks again.&nbsp\\;

 

What about DOT 4 residue in the line mixing with the DOT 5?&nbsp\\;\\\\\\;