It is summertime again, and I have this bizarre problem with my '95 Accord DX. I have
noticed the last two summers that my brake pedal will go soft whenever I am running
the air conditioner. This is a hot weather problem. It never happens when it is cool
outside, and I have no reason to run the air conditioner. I am between jobs right now,
so I really do not want to spend money on a part that does not fix the problem. I put off
the problem last year because of tight finances. Now I am in worse shape, and I cannot
ignore the problem because the soft brake pedal situation also being worse now. I simply
cannot imagine why these seemingly unrelated systems on the car would have this
freaky relationship. If the air conditioner is OFF... my brakes are always fine.

Ya gotta love Murphy's Law.

I know it is probably a worn master cylinder, but I would like some extra input.

Does anyone out there have any expert opinions on an efficient course of corrective
action? I cannot just throw money and parts at the problem until hitting upon the
right thing. My Accord is paid for and runs great in every other aspect so I need to
keep it around.

 

Wow... it's going to take hours to sift through all the responses. Thanks.

 

Have you ever bled your brakes? You should bleed your brakes at least once every two years. Brake fluid absorbs water, when it is warm out it is easier to overheat contaminated fluid(brown/green). This causes the spongy pedal. If your fluid is not clear then it most likely needs to be changed. A large bottle of fluid costs about 5-bucks from the local ORLY/Otterzone.

 

I have not, and it is something very affordable to do just for preventive maintenance. However, if I turn my air conditioner off the weird soft brake pedal problem goes away
immediately. It's freaky, and I wish I knew why this relationship exists.

 

With the A/C on it ads a load to the engine. It may be affecting the amount of vacuum that the brake booster 'sees'. Can you beg/borrow/steal a vacuum gauge? Hook it up to the intake manifold and see if the vacuum changes significantly with the A/C on or off. Does the RPM drop a lot with the A/C on?

 

I will try this out. It makes sense. My RPM does drop a lot when the A/C compressor
kicks on. I appreciate your input a lot. Thanks.

 

Could be that the idle compensator is not working correctly.