Car Repair Help by Professional Mechanics
Car Noises
/ Bubble Noise
Why Does My Car Make a Bubbling Noise?
Introduction - READ COMPLETELY BEFORE BEGINNING
Many bubbling noises are created when air is trapped inside a liquid container
such as the heater core. If this air is not allowed to exit the system, fluid will
trap air causing a bubbling noise while the system is in operation. Also, depending
on the system in question air can impair the operation of that system. Systems where
air can affect the operation or cause bubbling includes: brake, clutch, steering,
transmission, cooling and heater systems.
Bubbling Noise
In this section we will give you instructions on how to check for air in a particular
system. Problems can range from installing a fluid restriction devise to bleeding
the hydraulic brake system. Below we give answers to common problems to "air in
the system" malfunctions.
- Air in Brake System: Air can get trapped inside of the
brake system due to a leaking master, wheel cylinder, brake 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.
Brake Master Cylinder
- Air in Cooling System: The
engine's cooling
system used to transfer heat from the
engine to
the radiator
by the cooling
system.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
your engine over heats 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) is being generated will cause bubbles in the cooling system.
Complications from these bubbles can include: overheating, thermostat operation
malfunction and coolant displacement. Once a cooling system is empted sometimes
it can be tricky refilling the system. Due to the design of the cooling
system air is sometimes naturally trapped inside the system so look for “bleeder”
screws on the cooling system components, they are there to let the trapped air
out. Sometimes it can take several cycles of the system
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 component has failed. When a CO2 leak first develops
it may or may not cause the engine to overheat. For more information check,
engine
over heats.
Radiator Cap and Coolant Reservoir
- Air in Heater System: Air in the heater system (core) can
be caused by excessive coolant volume being pushed through the core. This heater
core is design to have "restricted" coolant flow to minimize cavitation. This
cavitation can cause the heater core to extract air from the coolant much like
a boat can cavitate a prop. To repair this condition a flow re-stricter must
be installed on either the core input or out hose. Refill cooling system normally,
recheck as needed.
- Air in Clutch System: Some standard transmission car manufacturers
use a hydraulic actuation system much like a brake system would use. Like a
brake system, a clutch system can exhibit the same bubble noises for the same
reasons. Check the fluid level of the clutch primary cylinder. If the primary
cylinder is low it will cause the system to take in air causing a bubble sound
while in operation (pressing the clutch pedal down). There is no reason for
a large amount of clutch fluid to disappear like a brake system (A brake system
is subject to brake calipers that fill with fluid as the brake pads wear) if
the fluid level is down it is because the system is leaking and needs inspection.
Repair and bleed the system as needed to recheck system.
- Air in Power Steering System: The power steering system
utilizes hydraulic fluid to transfer force from the
power steering
pump, the rack and pinion or steering box, without fluid the system cannot function.
If the fluid level is low it can pull air into the system causing a whining
noise due to the bubbles in the system. Check the power steering fluid level
by locating the power steering fluid reservoir and remove the cap (twist counter
clockwise). Most systems have a fluid level dip stick mounted inside the cap.
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 then start
engine (hands
away from engine) and turn
steering
from lock to lock several times. Shut the engine off and recheck fluid level,
allow system to stand for a period of time to allow air in the fluid (aeration)
to dissipate. Check fluid level and re-top as needed.
Power Steering Cap
-
Air in Automatic Transmission Fluid: An automatic transmission
functions by automatically changing the gear ratios while determining the speed
and load of the engine. A torque converter utilizes transmission fluid as a
coupling agent allowing the engine to run while the car is stopped without stalling
the engine, then re-engaging to make the car move again once the RPM of the
engine has increased. 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 while the dipstick has being removed.
Add transmission fluid as needed to obtain the correct level. Check the system
for leaks and repair as needed.
Locate and Remove the Transmission Fluid Level Indicator
For manufacturer specific procedures for any of the steps above please visit
our car repair
manual page.
Car Noises /
Bubble Noise
Check Manufacturer Specific Bubbling
Noise Questions and Answers
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