Coolent System Questionable

So my coolent system has me under suspicion. The coolent is leaking not a lot but seeping from the radiator cap and the hose that goes into the reservoir. Last year had water pump replaced this month had a coolent flush. Truck is holding coolent levels fine not overheating or anything but before I face a legit breakdown trying to figure this #### out btw it’s a 2017 Freightliner Cascadia w/501,525 miles. I’m suggesting it’s either the radiator cap needs replacing of thermostat hopefully it’s sum like that on the inexpensive side before I drop a few thousand into a radiator please let me kno sum

 

Coolant looks black. Could be EGR cooler pressuring system. Also maybe injectors cup seals, was on mine.

 

Looks to me like possible over filling.

 

Injector cup seals?? What’s that?? N where is it at how much it cost and can I do it myself

 

Plus coolent is new just had system flushed n new fluid replenished literally like last week at dealership

 

Nahh the level is right jus had a coolent flush at dealership I double checked it to make sure it wasn’t over filled

 

Actually Brother, I think you meant injector o rings. Compression leaking past o rings will cause darkening of coolant. Cascadia surge tanks are very prone to cracking and leaking. Usually, if engine was pressurizing coolant system, the bottom half of that surge tank would fill with coolant. That seam in the tank is actually a coolant passage leading from top tank to bottom tank.

 

I Would think that the pipes/rubber hoses on your overflow tank are PLUGGED.

 

Yes probably o-rings. Never saw the paperwork as it was warranty. I had diesel fuel in mine

 

As dark as it looks it could be an oil cooler leaking