Q: Brake Booster potential leak.

asked by on

After noticing a slight to moderate smell, which sort of smells like melting crayons, I dug around inside the cabin of the V70 to find the source. I discovered that there is a very slight leak around the brake pedal and push rod assembly where the brake booster passes through the firewall. Seems that hydraulic brake fluid is seeping through the booster, maybe around it, such that the grey bellows around the booster and push rod are wetted. Slight drops have traveled from there to the steering column cover. While the fluid is not particularly smelly when fresh, my assumption is that the fluid is breaking down causing the odor. Brake reservoir is still filled to appropriate level. Clearly something needs to be replaced, questions are... Can the brake fluid travel past the booster into the cabin? If so, does it travel through the booster or around it? Can the booster be replaced without removing the MC, it seems not? Is there a way to check the seal of the MC without removing it?

My car has 108000 miles.
My car has an automatic transmission.

Hi and thanks for contacting YourMechanic. If the brake pedal is easy to use when the engine is running and is stiff when the engine is off, then the brake booster is working fine. The oil is coming from the master cylinder rear seal and the master cylinder needs to be replaced.

Make sure that when you replace the master cylinder to bench bleed the master cylinder to remove all of the air from the inside of the master cylinder. Then after you hook up the lines, you will need to bleed the brake system to ensure that there is no air in the system. If you need further assistance diagnosing your brake system, then seek out a professional, such as one from YourMechanic, to help you pinpoint the problem and follow through with repairs.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Brake Booster potential leak.

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: Is a leaky brake booster unsafe if fluid level is o.k.?

If your brake booster is leaking but your brake fluid level is full, your brake booster would be leaking vacuum. This would mean that your booster has a crack, the check valve is bad, or the hose that connects to...

Q: Repaired ABS module installed, but lights on and not shifting properly

Hello. This can be caused by a few different things, but most of the time it is caused by the transmission speed sensors. I usually test the sensors first and replace them if needed. This is going to be the...

Q: Light bar installation

You should not have to go to a dealer to have the light bar installed. Check around in your area to find a good automotive custom shop or a specified Mustang custom shop. They would be happy to install the...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
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...
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...