I have a coolant smell coming from the right front corner of my 2016 SL550 after driving it. There is no loss of coolant that I can tell and no evident coolant leak. I did notice today that right after I shut it down there is a faint hissing sound coming from the cap. I’ve done some research on this and have seen opinions that this smell is normal and is caused by venting of the coolant when it is hot. I find that hard to believe, but I guess you never know. I have ordered a new cap but I am generally not that lucky. Has anyone else experienced this?

 

Locate the circulation pump. If it’s on the right side, that is a suspect component.

My circulation pump has wafted coolant vapors since new, it is located behind the left (driver’s) side headlamp. It’s a cheap parts bin component used across many MB powertrain a and platforms. Crusted coolant can be seen on the hose connections on the circulation pump.

”Normal” according to the MB dealer.

 

Did you check intercooler coolant level under engine cover?

 

I have not but will look at it tomorrow. Thanks for the suggestion.

 

It’s easy to overlook, many people don’t even realize it’s there.

 

I had a coolant leak that I didn’t notice for a while because the coolant had pooled up on an underpanel. I would make sure they are clean.

 

Thanks for the suggestion, I’ll take a look.