Hydroboost Troubleshooting for Hot Rods and Muscle Cars
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Adding hydroboost brakes to your hot rod, muscle car, or classic truck can be intimidating. There are countless horror stories of bad installs leading to moaning or chattering pumps, poor steering feel, and unpredictable brake pedal feedback. Why is it so difficult to get hydraulic brake assist to work right? Oftentimes, the power steering pump and reservoir (supply side) are underestimated.
Your steering is a closed-loop system that includes a steering gear, a pump, and a reservoir along with feed and return hoses. The pump is designed to supply sufficient pressure and flow to support only one component: the steering gear. The reservoir stores enough extra fluid to support the steering system.
So what happens when you add a second load to the existing steering system in the form of a hydraulic brake booster? Many people assume that the power steering pump will just step up to support both loads—steering and braking. Likewise, it is assumed that fluid reserve capacity will be adequate for both steering assist and brake assist.
When adding a hydraulic brake booster (aka hydroboost brakes) to an existing power steering system, the added load will likely tax the system. The hydraulic brake booster most definitely robs some of the pressure and volume from your power steering system. Both sides of the system can end up compromised.
Making matters worse, steering assist and brake assist are both variable-pressure mechanisms. Power steering pressure can spike during aggressive, high-speed cornering. Rotating the steering wheel quickly can cause a spike, as will hitting the steering stops. Autocross is a great example. Hydroboost is less likely to cause pressure spikes, but if you crank the steering wheel while applying the brakes, as in an emergency avoidance situation, both systems may spike simultaneously.
Whether you're still in the shopping stage or troubleshooting an existing system, consider a high-capacity dual-return-port power steering reservoir.
1) Your combined system (steering + brake booster) requires additional fluid reserve capacity. That means a bigger power steering fluid reservoir with more capacity.
2) Your combined system really should have separate return lines: One for each system.
Can I use a tee fitting for my Hydroboost brake return line?
If your hydraulic brake booster supplier sold you a tee fitting to splice into your existing power steering return line, fluid pressure may backfeed rather than return to the reservoir. That backfeeding may lead to undesirable steering or braking response.
The best recourse when plumbing a hydraulic brake assist system is to eliminate the tee fitting completely. Plumb separate return lines to a large capacity baffled reservoir with dual return ports. With a Concept One remote dual port reservoir, once fluid passes through the baffles, it cannot backfeed. Many enthusiasts have improved their installations simply by switching to our dual-return reservoir. It works great. The next variable is just as important.
Power steering pump pressure and flow
If you have not yet purchased your accessory drive, consider the power steering pump's valving. It is critical to ensure that your pump is valved to match your steering gear plus hydroboost, if so equipped. There's a good chance your existing power steering pump may need to be revalved to ensure proper pressure and flow. When you order a Concept One accessory drive, we ask you for: 1) Your vehicle's steering gear type, and 2) if you are running hydroboost. We then match your pump's pressure and flow characteristics accordingly.
If you are planning to buy another brand of accessory drive system, be sure to ask them about the power steering pump pressure and flow. If they cannot custom-valve your system, or don't understand the question, it's best to reconsider your purchase. You absolutely want great, positive steering-wheel and brake-pedal feel. Both are critical to your driving experience.
If you already purchased another brand's accessory drive system and are adding hydroboost, you might get lucky. Many of the mass-produced accessory drive systems sold today come with overboosted pumps to "play it safe". Without hydroboost, you may not like the steering feel and feedback of these overboosted pumps. Add on Hydroboost, and your steering response may actually improve. In this situation, you may just need a dual return reservoir.
Conversely, if your power steering pump is valved on the low side, it may not like the addition of hydroboost. Your best bet is to revalve the pump. If you are adding hydroboost to an existing Concept One system, we are happy to revalve your pump at no charge. We can also provide you with a re-valve kit if you like to tinker. Either way, we want you to have perfect steering and braking feel.
Ultimately, your hot rod hydroboost and steering systems can work together in harmony. Pressure, flow, reserve volume, and plumbing are important factors. Correct power steering pump valving and a dual-return-port reservoir will get you closer to that goal.
In this article:
Dual Return Port Remote Reservoir
Replace the T-fitting in your hyddroboost system to isolate your vehicle's power steering return line from its brake assist return line. CNC machined from solid 356-T6 aluminum and available machined, black anodized, or show polished.
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Concept ONE Pulley Systems
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