Coolant Reservoir Leak?

Coolant is leaking a bit from the sensor on the reservoir. I noticed it a couple days ago. The plastic nut was loose. I tightened it with my hands because I don’t have a socket that size. The size is over 40 mm. This is on a 2014 Freightliner Cascadia with a DD15.

I’m hoping I don’t have high pressure in the system. What’s an easy way to find out if I have high pressure?

 

I remembered I have some jumbo crowfoot wrenches. I was able to make a 1-7/8” fit, but it seems like a 48mm is a better fit. I think it won’t leak anymore. On a second thought, I could have used my large crescent wrench.

 

I couldn’t close it well by hand because it’s pushed into the reservoir, making it hard to turn. I was careful not to over-tighten it with a crowfoot wrench by hand.

 

So I have an extra sensor in my truck, but the one I have on right now is only one year old. The dealer replaced it while repairing my truck. It turned out that wasn’t the problem as it’s only a coolant level sensor. Talk about replacing parts that aren’t even necessary. Dam, dealers. They should know better.

 

I remember mine being much cheaper than that. I’d say around $75. It turns out it doesn’t have a gasket, only an o-ring.