Is it absolutely necessary or recommended to drain brake fluid before replacing the brake pads?

 

No / no. There is a recommended brake fluid change interval, can't remember what it is - have never done it in any of my cars, with a few going over 100k miles and zero problems (Accord, and '95 Maxima). Theoretically water can get into the fluid and cause rust, dirt can cause problems...haven't seen it

One thing you should do is watch the brake level in the master cylinder. If you've added fluid, it may overflow - and brake fluid eats paint.

 

Thanks G35Now. You are always one of the first to reply to threads. Awesome!

 

brake fluid should be changed every 2 years with normal driving .. obviously more if you track it

and no its not necessary to change to fluid before or after the pad/rotor change

edit : i only suggest not topping off brake fluid due to the fact that 99.9% of the time your fluid is low due to the fact that your pads are getting low .. which is causing the caliper piston to be pushed out more .. which leads to more fluid in the caliper/lines

fluid could be low due to a leak .. but then you would have soft/spongey, low performed brakes

brake fluid low = brake pads low

 

Awesome. Thanks. I asked because a guy at work told me I had to drain some fluid so that when I push in the piston, the master cylinder won't overflow. So, brake fluid level is proportionate to brake pad level as long as no leaks are present in the system.

Thank you.

 

It's possible for the fluid to overflow while compressing the caliper piston if you had the fluid flushed/bled in-between a brake job, and the person filled it to the max line.

 

I replaced my pads a month ago and the brake fluid overflowed when after I pushed the pistons back, probably because i topped it off about 6 months ago. Not a big deal though...you can dab some paper towels to soak up the extra fluid. Or (even better!) bleed your brake lines before you start...it'll get rid of the extra fluid and air in the lines.

 

/\+1

Brake fluid is designed to absorb water and thus needs to be changed relatively frequently to maintain top performance and avoid corrosion of seals, etc. in the braking system.

 

Not theoretically, brake fluid is hygroscopic and will absorb moisture. If you would like a little tutorial about brakes you can download and read my article from Sport Z Magazine here:

http://www.fourproducts.com/Development_of_the_FSBC.pdf

Ok, so maybe it is an obvious plug - but I put together a LOT of information for the article.

J