Good day Tsikoters! 1st Gen Kia Sportage here with R2 diesel engine. I notice that after the engine is turned off, there is a hissing sound for a few seconds. It seems to be comming from the air cleaner intake. But ut could also be coming from the hydrovac, I'm not really sure since they are located close to each other. Any idea what could this be?
Listen where the noise is coming from using a stethoscope or a short plastic hose. Trace the area that makes the loudest noise. If the engine is already off by then, the cause might be the pressures equalizing in the a/c lines or the compressor or it might have a leak in the brake booster check valve