7 Must Know Symptoms of Bad Hydroboost Duramax with Solutions

A hydro boost assists a driver in braking properly and efficiently.

It was first introduced in 1973 and is still used in most vehicles.

The function of a hydro boost is that it reduces the effort of the pedal and makes the brake operating system more straightforward.

Like any other part of a vehicle, hydro boost also has some problems and symptoms.

This article discusses the causes of the problems and possible solutions.

What is a Hydroboost on a Duramax?

What is a Hydroboost on a Duramax?

Hydro boost is an alternative to a vacuum booster.

The hydro boost assists the driver in applying brakes by using hydraulic pressure from the power steering system.

The difference between vacuum brake and hydro boost is that hydro boost operates by using hydraulic pressure instead of engine vacuum for brakes.

Hydraulic brake boosters work well, especially for diesel-powered vehicles.

Because the diesel engine has less engine vacuum compared to the gasoline engine.

That’s why diesel, supercharged, and turbocharged engines use a hydro-boost system rather than a vacuum brake.

07 Symptoms of Bad Hydroboost Duramax

Hydroboost malfunctions make braking difficult and dangerous.

It causes some problems, including reduced braking power, unusual sounds, fluid leaks, brake pedal problems, etc.

Here are the 07 symptoms of a bad hydro boost.

01. Braking Power Reduced

Braking Power Reduced

The major and most common symptom of a faulty hydro-boost is reduced braking power.

If the hydro-boost fails, the vehicle may experience reduced braking power.

You don’t get an immediate response when you hit the brakes.

There are other reasons for reduced braking power, so the problem should be identified first.

02. Noisy Booster

Unusual noise is another sign of a malfunctioning hydro boost.

A hydro booster typically makes a sound when pressing or releasing the brake.

But when the noise is unusual, it may be booster problems.

Typically a hydro boost creates hissing and clunk or clatter noise when operating.

This is normal if a hydro boost emits a hissing noise at 40-45 lbs. Brake paddle effort.

If the noise is coming from 20-25 pounds, there is a need to diagnose the problem.

At 50-100 lbs., clunk, clicking, or clatter noises will be heard if the hydro-boost is faulty.

03. Hard Brake Pedal

Hard Brake Pedal

If the booster fails to provide power to the brake system, pressing the pedal will be hard.

A hard pedal needs more effort to press.

Slowly this problem turns into reduced braking power.

04. Increasing the Braking Distance

Due to the faulty hydro booster, the braking power is reduced.

These will impact your stopping distance on the road.

Sometimes, the hydro-boost will fail, and you will not be able to stop the vehicle at the target point.

So, you must check the hydro-boost if you have a problem with long braking distances.

05. Warning Light

A faulty hydro booster causes brake problems.

Then your vehicle’s brake warning light appears.

Make sure you act as soon as possible after noticing the warning light.

Since hydro booster problems affect the brake system, they can have dangerous and costly consequences.

06. Fluid Leaks

Fluid Leaks

If any of the hydro booster’s parts seal or hoses wear out or rupture, they leak fluid.

The amount of hydraulic fluid leakage depends on the severity of the leaks.

The fluid leakage problem should be addressed as soon as possible because once the fluid level is low, it affects the whole brake system operation.

07. Overheated Hydro Booster

Overheating occurs outside the vehicle if the hydro booster is incorrect.

These high temperatures damaged the seal and spool vane of the hydro booster.

Why Hydroboost instead of Vacuum Booster?

Here are 04 reasons for using hydro boost instead of vacuum-

  1. The driver can easily brake with a hydro booster.
  2. There is no vacuum booster in diesel engines, or if one is present, not enough to provide sufficient energy.
  3. If a vehicle wants more than the assistance provided by a vacuum booster, then it uses a hydro booster.
  4. Finally, a hydro booster increases the overall performance of a brake.

How Do I Know if My Duramax Turbo is Bad?

A bad or faulty turbocharger gives the following 08 symptoms

  1. Reduced fuel economy
  2. Increased exhaust emissions
  3. Overheating
  4. Increased exhaust temperature
  5. Check the engine light
  6. Power loss
  7. Unusual noise
  8. Wear and tear.

How Do I Know if My Duramax Hydro boost is Bad?

A faulty hydro boost causes the symptoms mentioned above.

When you observe those symptoms, you can ensure the hydro-boost is working.

Here are the following 10 steps for testing a hydro boost-

  1. Heard the noise, whether it was normal or not. I already discussed hydro boost normal and abnormal noises in the symptoms section. Take a look to get a better understanding.
  2. Test the basic functions, like starting the engine and checking the brake pedal.
  3. Check if the hoses are damaged. If one is damaged, the other will follow soon.
  4. Check leakages
  5. Check bleeding; if the hydro-boost is wrong, it may self-bleed.
  6. Test the cooler
  7. Check if the master cylinder and the pedal are adjusted correctly.
  8. Test the belt
  9. Flush the system
  10. If possible, use owner manuals service information for an accurate test.

How to Replace Duramax Hydro Boost?

Typically, a hydro booster lasts over 50,000 to 70,000 miles.

However, some users reported that their Duramax hydro booster lasts over ten years.

Maintenance is key, of course.

If you find your vehicle’s hydro booster is faulty, you can replace it.

Here I divided the replacement process into 02 steps, step 1 and step 2, for clear understanding. 

Let’s discuss the replacement process

Materials Required

  • Flare nut-wrenches
  • Jack
  • Power steering fluid
  • Jack stands
  • Funnel
  • Safety glasses
  • Protective gloves
  • Screwdriver
  • Repair manuals (if available)

Step 1: Remove the Faulty Hydro Boost

1. Find the hydro-boost. You can find it on the driver’s side, attached to the firewall.

2. Disconnect the connecting wires

3. Remove accumulator pressure

4. Pull out the master cylinder

5. Detach the hydraulic lines

6. Separate pushrod and brake pedal

7. Unscrew the two hydro boost nuts

8. Finally, remove the faulty hydro boost.

Step 2: Install a Fresh Hydro Boost

  1. Put the new fresh hydro boost in the position of the old booster
  2. Screw the two nuts in the hydro booster
  3. Connect the brake pedal and pushrod
  4. Attached the hydraulic lines again
  5. Install the master cylinder
  6. Now start the engine and pump the vehicle
  7. With the help of a jack, raise the vehicle and bleed the system.
  8. Now ground the vehicle and test the power steering fluids
  9. Reconnect the cables.

That’s all; this way, you can easily replace the hydro-boost.

It costs you around $600 to $900 to replace a hydro boost.


What are the symptoms of a bad EGR valve Duramax?

Common symptoms of bad EGR valves on a Duramax are:

Increased fuel consumption

extremely rough idle at low RPM

Excessive emission

Knocking noise from the engine

Reduced performance

Check engine light on etc.

Look out for the symptoms and take action immediately to avoid any damage to other parts resulting in higher repair costs.

Can a bad Hydroboost affect brakes?

Hydraulic fluid pressure is the key to hydroboost power brake system. Power steering pump feeds the hydraulic fluid to the system. It boosts the force on the master cylinder’s brake fluid. More force means more pressure on the brake calipers. Lesser force means a less effective brake system.

Does Hydroboost use power steering fluid?

Yes, hydro boost uses power steering fluid. Hydroboost of a GM vehicle uses GM steering fluid. ATF should not be used in the system. It can cause foaming and swell the sealing.

What is the pressure on a GM Hydroboost?

General pressure on a GM hydro boost rates around 1300 to 1600 psi. It can maximize up to 2400-2700 psi which is twice or thrice times powerful compared to the vacuum booster. It is enough for most of the work including braking while towing.

Is Hydro boost better than vacuum?

Vacuum boost depends on the throttling of the vehicle. It is cheaper but heavy-duty vehicles are built on diesel engines. Diesel engines have no throttle therefore very low or no vacuum is produced. Hydro systems don’t have that disadvantages and are powerful compared to vacuum systems. Though hydro-boost is costlier than vacuum boost, it is better.

What happens if you don’t bleed hydraulic brakes?

Compressibility of the fluid is necessary for the hydroboost system. Air bubbles in the fluid cause issues with the fluid. As a result, you will feel the pedal to be in a lower position. You may also feel spongy during brake pressing. Brakes may need more pressure to work. So you should bleed hydraulic brakes.

Final Words

A hydro-boost is an essential component of your brake system.

It is important to take all symptoms seriously as they are linked to your driving safety.

The replacement of hydro boost is also costly, so maintain it properly for a longer lifespan.

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