Ok so i have a 94 cx and everytime its warm outside my brake pedal slowly sinks when im coming to a stop..and when im at a light and im holding the brake it sinks..sooo my question is..do you guys think i need to bleed my brakes or new master cylinder?? or booster

*ONLY DOES THIS ON HOT/WARM DAYS!

 

i would put my money on a failing master cylinder. go and check under the metal part of the master cylinder that meets up with the booster and see if fluid is leaking from there. with the installation of a new master cylinder the brakes should be bled anyways.

 

The rubber 1-way in the master cylinder is going out. Dont think they see rebuild kits,not to mention, i wouldnt do that anyways. Go ahead and replace the master cylinder & problem solved!

 

there is fluid leakin actually...how much do you estimate it will run for a new one?? and any DIY for installations?

 

master cylinder ... 99.9%...
you can buy the oem rebuilt replacement from advanced auto for 50 bucks with core charge.
fyi, the biggest bolt on master cylinder that will fit on your car is from the 91 civic ex.
your car should be 13/16ths
the 91 ex is a 15/16ths.
you need to buy a "brake line wrench". and its a 10 mm
and its pretty straight forward.

loosen all the lines going into the master cylinder with the brake line wrench.
then losen the nuts holding the m.c.to the brake booster.
insert the new m.c. the opposite of taking it off.
i highly reccomend using napa dot 4 brake fluid.
and be sure to have a buddy when bleeding the brakes.