C55 after rainstorm engine wont crank
ideas on what to do?
thanks
I have had my car not start after going through the car wash too often - nearest I can tell, the excess water caused a battery drain somewhere and everything would quickly go dead (parked either overnight or just a few minutes). The first time it happened, I traced it to a bad (shorted) alarm module. Fixed that and it happened again a couple more time. The last time it happened, I disconnected the battery, reconnected it and everything came back up and the car started. I suspect a relay sticks on, but hard to diagnose since it's unpredictable. Now I only wash the car every 3-5 days, carry a clamp meter and tools to disconnect the battery.
I have 2 out of 4 sunroof drains clogged. RF and LR drain fine. I need to pull the inner fenders and ream out the other 2 drains from the bottom. This is most likely the cause.
In case you don't realize it (and I've recently learned myself), the sunroof seal isn't really designed to truly seal - just keep the wind noise down and the MAJORITY of the water out. There are essentially gutters around the opening leading to drains in all 4 corners that dump the excess water out in the wheel wells behind the inner fenders.
I just had to do extensive repairs to my spare vehicle (2009 Audi A4) thanks to sunroof drains. All 4 drains were clogged and both rears leaked where the tube comes into the sunroof gutter, making the interior moldy and causing all kinds of corrosion and havoc in the trunk electronics bays. The trunk had 2" of water under the spare tire and another 1" in either side electronics bay. I had to drop and replace the headliner, pull the inner fenders and clean the rear drains from both directions and glue them back in place, then deal with drying everything out, removing the corrosion (Caig DetoxIT), and cleaning and replacing the affected seats. Even now, 2 weeks after doing all this work, electronics continue to fail from corrosion - I just lost the reverse camera the other day. A replacement is on the way.
Sunroof drains essentially made my car into the equivalent of a flood car... Don't underestimate the importance of clear sunroof drains!
Last edited by Spooky55; Jul 10, 2025 at 09:50 PM.









