Skip the auto shop - Our mechanics make house calls

Q: poor brake performance when car's ac is on

asked by on

When driving with ac system on. Usually in warm / hot weather. Braking performance is significantly poor. Pushing harder on the brake pedal doesn't seem to help. Wondering if this is common? How would I fix the issue?

My car has 230000 miles.
My car has an automatic transmission.

Hi there. Most of the time this is due to a loss of vacuum in the engine. A loss of vacuum drastically reduces the performance of the power brakes. I typically start by checking for any vacuum leaks in the engine. If there are none, then it may need a new vacuum booster. If you are going to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to inspect your braking issue and make any repairs that are necessary.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car vibrates when stopping.

Your problem is a common one. The vibration/pulsation you feel when braking is possibly due to warped rotors. Rotors are a smooth machined metal surface that your brake pads make contact with when you apply your brakes. When the rotor...

Q: Can I Get Cold Air Without Running the Air Conditioner?

All vehicles produced today are equipped with air conditioning systems. If you do not want the air conditioning on but you would like fresh air to come into the vehicle then all you would have to do is turn the...

Q: After replacing the power steering pump there was a low idle, idle screw is all out, running rich, and idle speed doesn't change.

Hi there. The engine has a vacuum leak and is causing the engine to stumble down on the idle. Check all of the vacuum hoses and the brake booster for any leaks. The engine is rich for it's not burning...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...