jr226

2014 ML350 Bluetec, Bluetec settlement completed 6 ish months ago.

Has anyone seen this before? I've got this buildup on the bottom of my gas tank, just noticed it after a 150+ mile towing trip. I touched it and it doesn't just rub off, but I could get it off with some elbow grease.

rapidoxidation

That's not your gas tank, that's your adblue (DEF) tank. The white stuff is crystallized DEF.
There's a leak somewhere and I bet it is covered by the extended warranty.
Edited to add: Unless those scuff marks are indicative of a hit that the cover and what's under the cover took.

chassis

Looks like damage caused by contact with terrain.

Diabolis

Second that - that is urea (DEF) crystallization. You have a leak.

jr226

Thanks everyone for the advice. I pulled the shield to look and cleaned off the DEF on the bottom of the tank. I don't offroad the vehicle, and I don't think any bump would cause the top to leak (the bottom of the tank looks just fine, no signs of impact at all).


I left it for a couple hours, then came back and followed the two tiny drips to the back of the tank. I pulled a big crystal chunk off the front passenger side of the tank. (its about 5-6" long)


It looks like its leaking from what I assume is the filler/ pump (2nd photo?). Can anyone confirm that the part is a pump or filler neck? I'm guessing this will be covered by the warranty, but I'll have to call the dealer to confirm. Thoughts?

chassis

It’s leaking DEF. It needs fixed. If the dealer thinks the damage is caused by contact with terrain there is a chance it won’t be covered. The greasy snake dealers attempt to wiggle out of anything.

rapidoxidation

The other option of course is to fix it yourself with better parts but that may void your warranty.

Diabolis

That looks like it is part of the DEF pump / heater assembly, which I believe is warrantied under the recall. If it isn't AND you want to work on it yourself, you can buy a Xemodex unit for about 1/2 the price (which is arguably better made). If it's the tank itself, I'd replace it with a brand new one. Depending on where you live, the tank may keep freezing and thawing in the winter... not the best environment for a plastic tank full of fluid that turns into ice and back.

The biggest issue BY FAR with working on it yourself is that while you have the pump / heater and/or DEF tank removed, whatever DEF solution remains in other parts of the system that are now going to be exposed to air will start to evaporate and crystallize there, and they can be much more expensive to fix (I'm thinking the heated DEF line and possibly even stuff upward). As you've noticed, DEF will crystalize as the water evaporates so you don't want to make create an additional $3K problem while trying to save $600 on what would be a $1200 repair by the dealer using original parts.

jr226

Thanks Chassis, rapidoxidation and Diabolis, I'm going to have the dealer look at it. Appreciate everyone's help!