A change in the way your brakes feel or behave is something worth paying attention to.
On vehicles fitted with a Hydraulic Brake Booster (HBB) or related electro-hydraulic braking system, symptoms such as increased pedal effort, unusual pump operation, warning lights or changes in brake assistance can sometimes indicate a problem within the hydraulic brake-assist system.
These systems aren't limited to one manufacturer or one type of vehicle.
Hydraulic and electro-hydraulic brake-assist technology can be found across certain Toyota Land Cruiser and Prado, Lexus, Mitsubishi Pajero/Montero and Toyota hybrid applications, among others.
And importantly, they aren't all the same system.
The components, control strategy and way a fault presents can differ significantly between vehicles.
At The Cape Brake Co, that's why our first question isn't simply:
“Is the HBB faulty?”
It's:
“Which system is fitted to this vehicle, and what is it actually doing?”
1. THE BRAKE PEDAL FEELS HARDER THAN NORMAL
One of the most noticeable symptoms of a brake-assistance problem can be an increase in the amount of effort required to press the brake pedal.
A brake booster is there to assist the force you apply through the pedal.
If the expected assistance is reduced, the vehicle may require considerably more pedal effort to achieve the braking response you're accustomed to.
This can potentially occur when a hydraulic brake-assist system isn't able to generate, store or deliver pressure as intended.
But a hard brake pedal does not automatically mean the HBB assembly has failed.
There are other braking-system faults that can affect pedal feel, so the cause needs to be established.
2. THE HYDRAULIC PUMP IS RUNNING MORE OFTEN THAN USUAL
On systems that use an electrically driven hydraulic pump and accumulator, the pump generates hydraulic pressure and the accumulator stores that pressure for use by the braking system.
The pump operating occasionally can therefore be completely normal.
What matters is a change in its behaviour.
For example, you may notice the pump suddenly:
- Running much more frequently
- Cycling after only a small number of brake applications
- Starting repeatedly over short intervals
- Operating when you don't remember hearing it before
This can indicate that the system is having difficulty maintaining the hydraulic pressure it expects.
But it doesn't automatically mean:
“The pump is broken.”
The reason for frequent pump operation can potentially lie elsewhere in the system.
3. THE PUMP RUNS FOR AN UNUSUALLY LONG TIME
Frequency isn't the only useful clue.
A hydraulic pump that operates for significantly longer than expected may indicate that the system is struggling to build the required pressure.
Depending on the particular system, possible areas of investigation can include:
- Pump performance
- Electric pump motor operation
- Accumulator condition
- Hydraulic leakage
- Pressure monitoring
- Electrical supply
- Internal hydraulic components
This is another reason listening to how the system operates, rather than simply whether the pump runs at all, can be useful diagnostically.
4. YOU HEAR BUZZING OR PUMP NOISES
Some hydraulic brake systems make noises during completely normal operation.
That's particularly important to understand.
Hearing an electric hydraulic pump doesn't automatically mean something is wrong.
For example, Mitsubishi's Pajero HBB system is designed to switch its electric pump on and off according to accumulator pressure. Mitsubishi's service information describes pump activation when pressure falls to approximately 16 MPa and switching off again at approximately 17 MPa.
What becomes interesting diagnostically is when the behaviour changes.
You might notice:
- Pump operation becoming much more frequent
- Longer pump cycles
- A different buzzing or electric-motor sound
- Pump operation after very few brake applications
- Noise that wasn't previously noticeable
If possible, record the sound on your phone.
An intermittent noise that disappears by the time the vehicle reaches the workshop can otherwise be difficult to demonstrate.
5. BRAKE, ABS OR STABILITY-CONTROL WARNING LIGHTS APPEAR
HBB and electro-hydraulic braking faults don't necessarily produce a dashboard light labelled “HBB.”
Depending on the vehicle, you may instead see:
- Brake warning
- ABS warning
- Stability-control warning
- Traction-control warning
- Brake-system warning messages
- Several warnings simultaneously
Some systems may also produce an audible warning.
The exact behaviour depends on the vehicle.
For example, Mitsubishi's Pajero HBB incorporates pressure monitoring capable of activating the brake warning lamp and HBB buzzer when hydraulic pressure becomes sufficiently low.
Other manufacturers use different warning strategies.
That's why warning lights need to be interpreted in the context of the specific vehicle and braking system.
6. BRAKE ASSISTANCE FEELS INCONSISTENT
Your braking system should behave predictably.
If the pedal suddenly feels different from one application to another, or the amount of assistance appears inconsistent, have it investigated.
You might experience something that is difficult to describe precisely:
“The pedal just doesn't feel like it normally does.”
That information is still useful.
You drive your vehicle regularly. A noticeable change in something as fundamental as brake-pedal behaviour shouldn't simply be dismissed.
7. YOU HEAR AN HBB WARNING BUZZER
This one is particularly relevant to certain systems.
Some HBB-equipped vehicles can provide an audible warning in addition to dashboard warnings when the system detects a significant problem.
The Mitsubishi Pajero HBB is one documented example. Mitsubishi describes a low-pressure warning function that can activate the brake warning lamp and HBB buzzer when accumulator pressure drops sufficiently.
If your vehicle produces a brake-system warning buzzer, particularly alongside changes in pedal feel or braking assistance, don't ignore it.
8. THE VEHICLE STORES HBB OR BRAKING-SYSTEM FAULT CODES
Sometimes the first evidence of a problem appears during a diagnostic scan.
Depending on the vehicle, stored faults might relate to:
- Hydraulic pressure
- Pump operation
- Pump motor circuits
- Accumulator pressure
- Pressure switches or sensors
- ABS operation
- Brake actuators
- Electrical circuits
- Control-system communication
Those codes are extremely useful.
But they're not necessarily replacement instructions.
A fault code tells us what the control system detected.
Diagnosis determines why it detected it.
WHAT ROLE DOES THE ACCUMULATOR PLAY?
The accumulator is an important component in many hydraulic brake-assist systems.
Its purpose is essentially to store hydraulic pressure so that the system has pressurised fluid available when required.
On the Pajero HBB, for example, Mitsubishi describes a nitrogen-charged accumulator used to store pressure generated by the electric pump.
If a system isn't maintaining pressure as expected, the pump may need to operate more frequently to replenish it.
That's why frequent pump cycling can be an important symptom.
But there is a critical distinction:
Frequent pump operation does not automatically prove the accumulator is faulty.
Pressure needs to be generated, stored, measured and controlled.
A problem at another point in that process may create similar symptoms.
ARE ALL HBB SYSTEMS LIKE THE PAJERO OR LAND CRUISER?
No.
This is something we want CBC customers to understand because the term HBB can cover related technologies that aren't mechanically identical.
A Mitsubishi Pajero HBB, Toyota Land Cruiser hydraulic brake booster and Toyota hybrid electronically controlled brake system can all use hydraulic pressure and electronic control in their braking architecture, but their components and operating strategies differ.
Some other vehicles use hydraulic brake boosters supplied through entirely different hydraulic arrangements.
So we don't diagnose every hydraulic booster according to one generic checklist.
We identify the system first.
DOES FREQUENT PUMP OPERATION MEAN I NEED A COMPLETE HBB UNIT?
Not automatically.
And this is particularly important because these assemblies can be extremely expensive.
CBC regularly sees customers who have been quoted R50,000 or more for complete replacement through the dealer network.
A pump running frequently may indicate a pressure-related problem, but it doesn't tell us by itself which component is responsible.
Depending on the particular system and fault, the appropriate solution could potentially involve:
- Repair of the existing HBB assembly
- Reconditioning
- A specific serviceable component
- Electrical repair
- Hydraulic repair
- Replacement of a particular component
- Or, where necessary, complete replacement
The diagnosis determines which route makes sense.
CAN HBB PROBLEMS GET WORSE?
A developing problem involving hydraulic pressure or brake assistance isn't something we recommend leaving indefinitely to see what happens.
These are safety-critical systems.
If pump behaviour has changed, warnings are appearing or the brake pedal feels different, have the vehicle assessed.
WHEN SHOULD I STOP DRIVING?
If the vehicle develops:
- A significantly harder brake pedal
- Loss or substantial reduction of brake assistance
- Significantly reduced braking performance
- Serious brake-system warnings
- An HBB warning buzzer
- Any situation where you're uncertain whether the vehicle will stop safely
don't simply continue driving it normally.
Arrange for the vehicle to be assessed safely.
WHAT INFORMATION SHOULD I GIVE CBC?
The more information you can give us, the better.
When contacting CBC about a possible HBB problem, send us your:
- Vehicle make
- Model
- Year
- VIN
- Current mileage
- Warning lights or messages
- Description of the pedal behaviour
- Description of any pump or buzzing noise
- When the problem occurs
- Whether the fault is constant or intermittent
If another workshop or dealer has already inspected the vehicle, send us any fault codes, diagnostic reports or quotations you've received.
Videos can also be extremely useful.
If your pump is cycling repeatedly or making an unusual noise, a short recording can give us valuable information before the vehicle even reaches the workshop.
CAN CBC REPAIR HBB SYSTEMS?
Depending on the particular system, nature of the fault and condition of the assembly, specialist repair or reconditioning may be possible rather than replacing the entire unit.
And this is where CBC's HBB specialism becomes particularly valuable.
We're not limiting that service to Land Cruisers.
We assess HBB and related hydraulic brake-assist systems across applicable vehicles, identifying the system fitted and determining whether the fault falls within the specialist repair work we can perform.
Where a repair is suitable, CBC can typically assist for around 60% of the cost of complete dealer replacement, although the actual cost depends on the vehicle and fault.
Not every unit is repairable.
But with complete replacement sometimes costing R50,000 or more, establishing whether a specialist repair is possible can make a substantial difference.
THE CBC APPROACH TO HBB FAULTS
Different vehicle.
Different system.
Different fault.
The principle stays the same.
IDENTIFY THE SYSTEM.
UNDERSTAND THE SYMPTOM.
DIAGNOSE THE CAUSE.
REPAIR WHAT ACTUALLY NEEDS REPAIRING.
Whether we're dealing with a Pajero, Land Cruiser, Lexus or another applicable hydraulic/electro-hydraulic braking system, we don't want to condemn an expensive complete assembly based on one familiar symptom.
We want to understand what is actually happening inside the system first.
RECOGNISE ANY OF THESE SYMPTOMS?
If you've noticed frequent hydraulic pump operation, warning lights, unusual noises, a change in brake-pedal feel or another braking-system problem, speak to The Cape Brake Co.
You don't need to know whether your vehicle has an HBB before contacting us.
Send us the make, model, year and VIN, tell us what you've noticed, and we'll take it from there.
Ask the Workshop Assistant or WhatsApp The Cape Brake Co.
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