Coolant lines at back of engine?
Thread Starter
Junior Member
Joined: Jul 2021
Posts: 65
Likes: 12
From: NW Florida
2012 E550
Coolant lines at back of engine?
I have a 2012 E550 bi-turbo and today after stomping the gas to get around slow traffic it sprung a massive leak. When I got home I let it cool down and started looking around, even getting under the car and removing the tray, but couldn't really see anything. I had a gallon of distilled water that I poured in the reservoir and it immediately started leaking out the back of the engine. It was still jacked up, so I quickly got under and tried to see anything but it is really difficult to see anything. Lowered the car and filled it up again just to make sure have the front lifted wasn't making the water rush to the back, and it started coming out the same area. It also seems to be coming from lower in the engine as I can't see any fluid on the trans or higher up on the back of the engine. There is some fluid in the valley towards the front under the cover, but it doesn't seem to be from this issue.
Is there something in the back of the motor that would cause a big leak like this, or should I be looking somewhere else? When I got the car at 75k miles, I had timing done, cam adjusters, one cam, and some other maintenance done and all the plastic coolant lines for the turbos were replaced.
Thanks
Is there something in the back of the motor that would cause a big leak like this, or should I be looking somewhere else? When I got the car at 75k miles, I had timing done, cam adjusters, one cam, and some other maintenance done and all the plastic coolant lines for the turbos were replaced.
Thanks
Out Of Control!!
Joined: Apr 2019
Posts: 12,170
Likes: 6,883
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
head rear leak
I have a 2012 E550 bi-turbo and today after stomping the gas to get around slow traffic it sprung a massive leak. When I got home I let it cool down and started looking around, even getting under the car and removing the tray, but couldn't really see anything. I had a gallon of distilled water that I poured in the reservoir and it immediately started leaking out the back of the engine. It was still jacked up, so I quickly got under and tried to see anything but it is really difficult to see anything. Lowered the car and filled it up again just to make sure have the front lifted wasn't making the water rush to the back, and it started coming out the same area. It also seems to be coming from lower in the engine as I can't see any fluid on the trans or higher up on the back of the engine. There is some fluid in the valley towards the front under the cover, but it doesn't seem to be from this issue.
Is there something in the back of the motor that would cause a big leak like this, or should I be looking somewhere else? When I got the car at 75k miles, I had timing done, cam adjusters, one cam, and some other maintenance done and all the plastic coolant lines for the turbos were replaced.
Thanks
Is there something in the back of the motor that would cause a big leak like this, or should I be looking somewhere else? When I got the car at 75k miles, I had timing done, cam adjusters, one cam, and some other maintenance done and all the plastic coolant lines for the turbos were replaced.
Thanks
- the Bank2 head plastic pipe adapter
- the firewall plastic elbow
- the rubber flex hose
- misc O-ring
- (exp-tank relief cap)
While back in there feel free to replace:
- (a genuine ECT)
- a vac-pmp check-valve
Last edited by CaliBenzDriver; Nov 13, 2025 at 10:51 PM.
Thread Starter
Junior Member
Joined: Jul 2021
Posts: 65
Likes: 12
From: NW Florida
2012 E550
After doing some looking around with the help of a borescope, the problem seems to be coming from the intercooler area. Going to work on it today to verify, but it kind of makes sense. I have a tune that is obviously pushing more boost and could have cause the plastic to separate from the aluminum. Also, I don't floor it much, but the last couple of times I did there would be smoke coming from the exhaust when I let off, so, I'm guessing, that would have been coolant getting in the intake. We'll find out today.
