Last week at Auto Studio a Volkswagen Polo was brought in after a customer reported that their car was creating a hissing noise towards the front of the vehicle as well as being underpowered.

Symptoms:

• Vacuum or boost leak
• Check engine light
• Loss of power

What can cause a hissing noise?

A common cause of a hissing noise can be either vacuum lines or boost lines. Over time the rubber hoses in your car can become brittle and start to harden. This will either crack or loosen the lines causing a leak.

How to fix a hissing noise/underpowered car?

Firstly, the car was scanned for any fault codes, in this case no codes were produced. The next diagnosis strategy is to load the car at a standstill. By doing this it will ensure that the problem is either a vacuum leak or a boost leak causing the hissing noise.

As predicted the hissing noise was coming from a hose at front of the vehicle. Now that the problem was found, we needed to pinpoint the location of the leaking hose. This is where a smoke test is highly recommended. By using smoke, we can charge the system to check for smoke from a leaking hose.

Shown in Figure 1 and Figure 2 is the hose causing the problem. It was found to be a hose after the intercooler to have a large split leaking boost pressure causing the vehicle to have a hissing noise as well as being underpowered.

Figure 1

Figure 2