Step by step repair guide on how to fix automotive bubble noises. This article
pertains to all cars.
Difficulty Scale: 3 of 10
Tools and Supplies Needed
- Protective eyewear and gloves
- Appropriate fluids
Begin with the vehicle on level ground, in park with the emergency brake on.
- Air can get trapped inside of the brake
system due to a leaking brake master, wheel cylinder, brake flex line, caliper or
other components such as an ABS controller or proportioning valve. When this condition
occurs it can cause bubble sounds when the brake pedal is depressed. To check for
this condition check the brake fluid level inside the master cylinder by removing
the master cylinder brake fluid cap. If the fluid level is low it can allow air
to be forced inside the system producing the bubble like noise. To repair this problem
refill the brake fluid and inspect system for leaks or wear. If any leaks exist
repair as needed and bleed the brake system. Visit -
Brake system bleed
Brake Master Cylinder
- The radiator removes heat from the coolant
by forcing air through the radiator fins. Without coolant your engine will over
heat and if left unattended severe engine damage will occur. When an engine overheats
it can force coolant into the overflow container which can create a bubbling sound.
Never check the coolant level until the engine has cooled completely. If the engine
is not overheating, air can be trapped or CO2 (exhaust gas) can cause bubbles in
the cooling system. Complications from these bubbles can include: overheating, thermostat
operation malfunction and coolant displacement.
Due to the design of the cooling system air is sometimes naturally trapped inside
the system so look for a “bleeder” screw on the cooling system components such as
the thermostat housing. Sometimes it can take several cycles of the system of being
hot and cold before air is completely displaced. If once the cooling system has
been purged of air the air bubbles return it could be a sign that the head gasket
or other engine components have failed. When a CO2 leak first develops it may or
may not cause the engine to overheat. Visit -
Radiator Cap and Coolant Reservoir
- Air in the heater core can be caused by
excessive coolant volume being pushed through the core. The heater core is design
to have a "restricted" coolant flow to minimize bubbling. To repair this condition
a flow re-stricter must be installed on either the core input or outlet hose.
- Some standard transmission car manufacturers
use a hydraulic actuation system much like a brake system. A clutch system can exhibit
the same bubble noises for the same reason as a brake system. Check the fluid level
of the clutch master cylinder. If the master cylinder is low it will cause the system
to take in air causing a bubble sound while pressing the clutch pedal down. If the
fluid level is down its because the system is leaking or the clutch disc is worn.
- The power steering system utilizes hydraulic
pressure which is produced by the power steering pump. If the fluid level is low,
it can pull air into the system causing a whining noise due to the air bubbles in
the system. Check the power steering fluid level by locating the power steering
fluid reservoir and remove the cap (twist counter clockwise). If the fluid level
is down or there is no fluid in the reservoir the system has a leak. Inspect the
entire power steering system: pump, hoses and rack and pinion or box assembly, replace
worn or broken components as needed. Refill system with manufacturers recommended
fluids. Allow system to stand for a period of time to allow air (aeration) to dissipate.
Power Steering Cap
- An automatic transmission functions by
automatically changing the gear ratios while determining the speed and load of the
engine. If the transmission is low on fluid due to a leak or service it will cause
the transmission to scavenge fluid while taking in air. This air in the fluid can
cause a bubbling noise when the dipstick is removed. Add transmission fluid as needed
to obtain the correct level or service the transmission. Visit -
Automatic transmission service
Locate and Remove the Transmission Fluid Level Indicator
Many bubbling noises are created when air is trapped inside a liquid container
such as the heater core. If air is not allowed to exit a system, fluid will trap
air causing a bubbling noise. Also, depending on the system in question, air can
impair the operation of that system.
- Bubble noises are usually caused by service neglect, to avoid these problems
regular maintenance is required.
Article first published 2016-02-03