ML63 AMG W164 water getting onto FRONT ECU

[drummerboy999]

If anyone can help me with this mystery I'll be extremely grateful! I'm the proud owner of a 2010 ML63 AMG since Nov 2017 - love the car except for the fuel consumption However I have an issue with water getting into the plug going into the front ECU. Now Ive read plenty about the water issues with the rear SAM but nothing about the front ECU. This is positioned behind the offside (drivers side on UK car) FRONT wheel arch, you need to remove the front offside wheel arch liner to get to it. So, the issue first manifested itself with the relay to the water pump staying on with the relay clicking after ignition turned off and key removed, and the water pump therefore continuing to run until the battery ran flat . Investigation led to a waterlogged plug into the front ECU, and once all dried out problem solved. However what we can't work out is how the water got behind the wheel arch, we are convinced its not come down the loom so we have a mystery. I could guess at jet washing under the wheel arch and maybe water somehow squeezing behind the wheel arch liner at high pressure and bouncing up onto the plug but that's a best guess. Then it happened a second time after I had no choice but to drive through a flood and same issue, we have a waterlogged plug into the ECU. Obviously I'd like to avoid it happening again. So am wondering if anyone else has experienced this (and solved it?) or can shine a light on the mystery? PS I don't have a sunroof so its not blocked sunroof drains ... cheers in advance Mark

 

[drummerboy999]

Hi all, a very delayed update on this if anyone is interested … I got the ecu out myself (the first time was main dealer doing the job), dried the plug out and all fine. Then discovered upon refitting the ECU back under the wing that possibly it hadn’t been properly slid back fully on to it’s retaining bolts so perhaps the top of the ECU had been touching against the inside of the wing. If so this would explain water running down the inside of the wing onto the ECU and straight down onto the plug. That’s my best guess. Anyway I refitted the ECU properly, checking it wasn’t touching the inside of the wing and have never had the problem again … and that was two very wet winters ago!

 

[Bobby Dazzler]

Hi all, a very delayed update on this if anyone is interested … I got the ecu out myself (the first time was main dealer doing the job), dried the plug out and all fine. Then discovered upon refitting the ECU back under the wing that possibly it hadn’t been properly slid back fully on to it’s retaining bolts so perhaps the top of the ECU had been touching against the inside of the wing. If so this would explain water running down the inside of the wing onto the ECU and straight down onto the plug. That’s my best guess. Anyway I refitted the ECU properly, checking it wasn’t touching the inside of the wing and have never had the problem again … and that was two very wet winters ago!

Thank you for sharing.