Towards the end of the 1990s, BMW introduced a technology called the DISA (Differenzierte Sauganlage) valve. It was the German manufacturer’s take on a variable-length intake manifold and featured on most of its cars over the next decade. While the BMW DISA valve brought added performance and efficiency, it also came with its share of problems.
This article covers everything there is to know about the BMW DISA valve — from what it does to the signs you should look for with a failing unit.
What Does a BMW DISA Valve Do?
As mentioned above, the BMW DISA valve is an iteration of a variable-length intake manifold. A DISA valve alters the length of the intake manifold according to engine speed, optimizing airflow to the engine and allowing for better power, torque, and fuel efficiency across the rev band.
The system on the BMW employs a flap that opens or closes, shortening or lengthening the path that the air takes, thus timing when the air hits the intake valves. When the DISA valve is closed, the air is forced to take the longer route, which is the default position in lower RPM. At higher RPM, the valve is open, allowing air to take a shorter path that results in it being pressurized and more easily combustible. As you can see, the system’s working is relatively straightforward and controlled by the ECU.
Which BMW Engines Use a DISA Valve?
If you drive a BMW E36 or E46 3-Series, E39 or E60 5-Series, or one of the ‘X’ models produced between 1996 and 2006, it likely features a DISA valve.
The BMW DISA valve was first introduced in the later iterations of the BMW M42 engine. It came into broader use aboard the BMW E39 5-Series in 1995 and eventually made its way onto the BMW M54 engine, after which it was discontinued in 2006.
While the particular technology was no longer in use, it allowed the manufacturer to develop more modern versions, like DIVA (Differentiated Variable Air Intake) that was used on the BMW N62 engine, where it was the world’s first continuously variable length intake manifold.
Signs of a Failing BMW DISA Valve
A BMW DISA valve that’s functioning well plays a notable role in improving performance and fuel economy. As you can imagine, one that’s failing will result in several symptoms that can hinder the normal usage of your car. Additionally, while BMW DISA valve failures are not very common, they can cause serious damage to the other components in your engine if they fail. Here are some of the most common symptoms you will experience with a faulty BMW DISA valve:
Rattling Noise
The DISA valve is a plastic flap inside your car’s intake manifold. If it breaks, it can result in a rattling noise from the intake system. Over time, the seal formed when the valve is open or closed can degrade, causing the flap to rattle when air is drawn into the engine.
Power Loss
When your BMW DISA valve starts to fail, you will also begin to experience a drop in performance. You’ll notice that your engine cannot produce similar power levels higher up in the rev range and low-end torque. Both these symptoms result from a faulty DISA valve causing an air leak in the intake manifold. Unfortunately, the only way to resolve this is to replace the DISA valve.
Drop in Fuel Efficiency
As the engine no longer receives optimized air levels and pressure, it cannot combust fuel effectively. This results in a drop in fuel efficiency. Most owners who face BMW DISA valve issues have reported that the gas mileage of their cars reduced by about 30%.
Check Engine Light Illuminates
In some cases, your car might warn you about a faulty DISA valve with an illuminated check engine light (CEL) before you experience any of the other symptoms. If you see that the CEL on your car is lit up, you can confirm the issue by plugging a diagnostic device into the car’s OBD-II port and scanning for trouble codes. Some of the more common ones you’ll see in the case of a DISA valve failure are P1083, P1084, P1347, and P1348.
Can You Drive without a DISA Valve?
While you can drive without a properly functioning BMW DISA valve, we strongly urge you against doing so for extended periods. Even if you can ignore the drop in performance and fuel efficiency, a broken flap from a failing DISA valve can disintegrate and send bits of plastic and metal into your engine, which can cause tremendous damage.
BMW DISA Valve Replacement
The BMW DISA valve on your car should last between 70,000 to 100,000 miles without causing trouble. The likelihood of DISA valve failure is higher once you’ve breached the 100,000-mile mark. Beyond this point, you should carry out regular checks on the DISA valve to ensure it’s in good health.
When your DISA valve fails, the solution will depend on which engine you own. For instance, the BMW DISA valve on older engines, like the M52, comprises multiple components for which you can get replacements. So, if the seal or flap fails, you might be able to resolve the issue by replacing just the affected component.
However, if multiple parts need to be changed, you might be better off replacing the entire unit. Check out our selection of DISA valves and avoid dealership markups!
To replace the BMW DISA valve:
- Access the DISA valve housing. Typically, you’ll find the BMW DISA valve inside a black box bolted onto the intake manifold.
- Gain access to the valve by undoing the wire harness, hoses, and clips that hold it in place.
- Ensure that you cover the air intake when you remove the intake hose to avoid dust or other small components that you may be working with from falling into the intake.
- The valve is held in place with two bolts; removing them will let you remove the DISA valve.
- Replace the DISA valve and reconnect the components you removed, and you should be good to go.
Get A New BMW DISA Valve Now!
If you’re facing issues with your DISA valve, replacing the faulty unit with a genuine BMW part is usually the best course of action, as these parts were specifically tested and designed to perform with your engine.
That said, if you want to save a little money, you can opt to replace the broken BMW DISA valve on your car with an aftermarket unit. However, you must get one from a notable company. Bimmers.com stocks replacement DISA valves from BMW and reputed aftermarket names like Febi-Bilstein and URO. These aftermarket parts are priced between $100 – $150 but undergo extensive tests before they are brought into the market.
While you could find cheaper alternatives, they could cause severe damage to your engine if they fail unexpectedly. That’s why it’s always a good idea to stick with names you trust. To see all the parts Bimmers.com currently has in stock for your vehicle, simply use the year and model of your car on the website.
