finding a water leak into the cabin

[FNG]

Hope the hive mind can help.

I've got a 325ti which, as far as I can recall, has always been watertight and doesn't steam up. But when I bought the car, it had a ruddy great crack in the windscreen.

In December, I got the screen replaced as the MoT was due.

Since then (it's my impression that it's only since then, but I have been wrong before) it's steaming up overnight. I've got a silicone bag in there now to keep the windows clear.

I've been back on to the national windscreen fitting company and they won't have a bar of it.

So, is there a good way of finding a water ingress path, whether it's the screen or elsewhere?

Would a smoke bomb find the sort of leak that could be letting enough water in to cause this, but not enough that I can find it with a jet wash?

[Belle427]

Smoke would work but if its wet under the carpets its a vicious circle of that causing more condensation.
Check the usual areas under the bonnet for leaves etc and under the boot carpet.

[GreenV8S]

Check the debris trap for the cabin air intake. This would normally have a drain at the bottom, but if that's clogged then it can fill with water. Depending on the vehicle the water might overflow into the fresh air intake, or just leave you drawing in very damp air.

[Smint]

Presumably you've lifted the carpets and checked the floor is completely dry, might need to prop the carpets up and stick a fan heater inside for a couple of days to get it fully dry, check boot plus spare wheel tray if applicable and under back seat too in case its coming in at the rear.
Removing trims from firewall/bulkhead area might reveal obvious water trails on the bodywork.
Sunroof? are the drains clear.

Feeling agile? climb inside the car upside down with decent torch and get someone to play a hose over the car concentrating the flow on where you happen to be, under the dash is obvious first place to look.
Fully dried out leaving the carpets propped up you'll quickly see if any water appears in the footwells during the drenching.

[Glassman]

Water test is the only way. Badly replaced windscreens will usually leak from just above the rear view mirror. If no show there, remove the A-pillar trims, and pull back the carpets in the footwells and kick panels. Have someone aim a stream of water around the windscreen edge while you look for water appearing inside the car to see if you can track the entry point. Dabbing dry tissue on the inside edges of the windscreen might show something if it's not obvious to the naked eye.

If you have compressed air, blowing inside the windscreen at the adhesive with the outside edges sprayed with a soapy liquid is also a good way.

[p4cks]

I successfully found a water leak on a window seal on a using the smoke technique - although I used an actual smoke machine (a cheapo Amazon one)

[FNG]

Thank you all for replying.

Had a chance to take a look - I should have thought about the HVAC intake plenum tray drains - both partially blocked.

Great idea about blowing at the screen adhesive from the inside with compressed air. If this doesn’t cure it I’ll do that next.

Being cheap and lazy I was kinda hoping someone had successfully used a smoke bomb for eg finding leaky flues, but nervous about using that in my cabin and ruining st

Here’s hoping I’ve found the issue but some good ideas if I haven’t.