03' Sable Brake / Air Conditioning Problem


I recently bought a 03’ Mercury Sable that I love. Now that the temps are getting into the upper 90’s I’m having to run the A/C.

When I have the A/C on for about 10 minutes and I go and press my foot on the brake pedal it makes a squishy noise.

When I turn the A/C off, it takes about 15-20 minutes for the noise to go away.

My mom has a 97’ Thunderbird and has this same exact problem.

Can anyone help? I need my A/C this summer.


Can think of no reason why having the AC on would change any noise that pressing the brake would generate. This concern is going to require “ears on” diagnosis. Tell this story to your trusted mechanic post back his reply. Would you be willing to pay any diagnostic time to get a answer? A “squishy” noise heard inside the car. I conclude both the brakes and AC operate normally,let us know if this is not the case.


I’m not sure what this ones about either. Clogged AC drain?

Turn the AC on & leave the car parked & idling for 5 minutes, is there a puddle under the car from the AC.

There should be.


There is one thing that are shared by the brakes and the A/C on many cars and that is the vacuum system. The brakes use it for power and the A/C uses it to control the blend doors. I am going to suggest that maybe when the car is warm and the A/C running then you hit the brakes, that reduces the vacuum and causes the blend door to move (cutting off the A/C if it moves enough) and in fact what you are hearing may be that blend door. If I am right and if you hold the brake for a while you may well be able to feel the air conditioning decrease.