FAQ
TL;DR: In Mk4 Golf/Leon cases, 99% of cabin water comes from a leaking door carrier plate after window-mechanism work; “tighten the silicone and it will be well.” [Elektroda, moto-kord, post #16775085]
Why it matters: This FAQ helps VW Golf IV owners quickly find and fix wet-floor leaks without trial-and-error.
- Typical culprit: door carrier plate seal after regulator repair; hose-test the window before tearing down more. [Elektroda, Mario-1990, post #16775168]
- Quick test time: run water on the glass for a few minutes with the trim off, watch the inner door. [Elektroda, Mario-1990, post #16775168]
- Floor plugs: missing/breached plugs behind the sill or A‑pillar area can flood carpets. [Elektroda, Bullseye, post #16790499]
- Replacement cost: OEM floor plugs are about 4–5 PLN each; sizes vary by opening. [Elektroda, moto-kord, post #16790615]
- Edge cases: rear lamp gasket or rear-wash tube leaks can carry water forward into the cabin. [Elektroda, marqqv, post #16774009]
Quick Facts
- Typical culprit: door carrier plate leak after window mechanism work; confirm with a hose test. [Elektroda, Mario-1990, post #16775168]
- Test duration: pour water on the window for a few minutes with the door trim removed. [Elektroda, Mario-1990, post #16775168]
- Floor plugs matter: missing plugs near the sill/A‑pillar can soak the passenger footwell. [Elektroda, Bullseye, post #16790499]
- Replacement plugs: expect about 4–5 PLN each at the dealer; pick size by hole. [Elektroda, moto-kord, post #16790615]
- Uncommon path: rear lamp gasket leaks can migrate water to the front floor. [Elektroda, marqqv, post #16774009]
Why is water collecting on the passenger mat in my Golf IV?
Most often the door carrier plate seal leaks, especially after a window regulator repair. Water runs behind the trim and onto the sill, then the carpet. One expert noted “at 99% you have water in the cabin” from this plate and advised resealing. [Elektroda, moto-kord, post #16775085]
How do I hose-test the door to confirm a leak?
Remove the door trim, open the door, and pour water on the exterior glass for a few minutes. Watch the inner door and sill for drips. If water emerges from the plate perimeter, the carrier plate seal needs resealing. "The leak will come out of hiding." [Elektroda, Mario-1990, post #16775168]
What is the door carrier plate?
It’s the metal panel that holds the window mechanism. If its perimeter seal is bent or disturbed during regulator replacement, water bypasses inside and spills to the threshold, then the cabin. Resealing resolves the ingress. [Elektroda, Mario-1990, post #16775168]
How do I reseal a leaking carrier plate? (3 steps)
- Loosen the plate, clean old sealant, and dry the mating surfaces.
- Apply a continuous bead of sealant around the plate perimeter.
- Refit and tighten evenly; water-test again before refitting trim.
“Loosen the sheet metal, tighten the silicone and it will be well.” [Elektroda, moto-kord, post #16775085]
Silicone didn’t last through winter—what sealant should I use?
Use automotive glass adhesive for a longer-lasting bond. One user resealed with silicone, saw the leak return after winter, then switched to glass glue with lasting success. [Elektroda, Mario-1990, post #16775168]
Could missing floor plugs cause a soaked footwell?
Yes. Owners found rubber floor plugs hidden near the sill and at the front threshold missing, which allowed road water to enter and flood the carpet. Replace the missing plugs to stop ingress. [Elektroda, Bullseye, post #16790499]
Where do I buy floor plugs and what do they cost?
Buy them at a dealer or parts counter. Expect roughly 4–5 PLN per plug, and note that openings take different plug sizes, so bring measurements. [Elektroda, moto-kord, post #16790615]
Could water be coming from inside the door even if outer seals look fine?
Yes. If the inner moisture barrier or carrier plate was distorted during previous door work, water can leak from the door interior into the cabin despite intact outer seals. [Elektroda, Anonymous, post #16774942]
What other leak paths should I check besides the doors?
Inspect rear lamp gaskets and the rear washer tube routed on the right side. Leaks there can carry water forward and soak the floor, even if the trunk looks fine. [Elektroda, Staszek49, post #16774821]
Should I suspect the heater core if only the passenger floor is wet?
Start by checking coolant level. If there’s no coolant loss, focus on water ingress tests like the door hose test and floor plug inspection before disassembling HVAC. [Elektroda, marqqv, post #16773916]
How can I dry the soaked carpet quickly without a garage?
First stop the leak. Lift the carpet and underlay, and allow airflow; partial disassembly may be needed. Tracing with dyed water helps verify the fix before final drying and reassembly. “Sometimes you have to disassemble half the car.” [Elektroda, Anonymous, post #16774325]
Can the trunk being dry rule out rear sources?
Not completely. A user with a dry trunk still faced front-floor wetness from other paths. Check door plates and floor plugs before fully ruling out rear-related leaks. [Elektroda, Bullseye, post #16774902]
