Skoda Octavia 2003 AUM 1.8T – Strong vacuum at oil cap after hose & hockey puck work

Hi everyone,

I have a 2003 Skoda Octavia 1.8T (AUM, 150 hp).
I recently replaced all the lower crankcase breather hoses (including the Y-pieces with restrictors) and cleaned the “hockey puck” breather valve. After doing this, I noticed a strong vacuum when removing the oil filler cap at idle.

Thinking the hockey puck might be faulty, I replaced it with a new Vaico unit — but the strong suction is still there.

Some details:

• PCV valve (06A 129 101 A) is still the original, but I cleaned it.

• Both my original and new hockey puck allow air to pass both ways when tested off the car.

• Idle is smooth, no fault codes, no oil leaks.

Questions:

1. Is noticeable suction at the oil cap normal for the AUM once the crankcase ventilation system is fully sealed and clean?

2. Does anyone have the correct hose/PCV routing diagram for this engine so I can confirm everything is connected correctly?

Thanks in advance for any help.