URGENT: Volvo vnl 2016 D13 loosing coolant; no visible leaks

Hi all!

i have my 2016 d13 volvo vnl with def deleted. 500k miles on dash.

its been a well maintained truck but for the past week ive been having to put a gallon or two of coolant a DAY, especially when loaded with 40k pounds. Coolant warning goes off as soon as coolant level on tank gets very low. No obvious leaks are visible anywhere. i bought a coolant pressure test kit and tested the system @ 15 psi for about half an hour and the pressure never came down also no leaks were visible either. I also tried putting a bottle on the coolant reservoir release valve to see if theres any coolant coming out from there and nothing was present. Every time i fill up the coolant again i do feel abit of pressure coming out of the reservoir when i remove the cap. I have also been noticing hard starts; Truck has cranks for a long time before starting up and idles rough for the first 3-5 seconds. I checked the air tanks for any coolant residue and none were present; Only minimal amounts of moisture. I checked my diesel tanks and no coolant is present there either. My oil level is normal and my oil cap has no presence of any sludge. There was no coolant present in the oil on my last oil change either. I dont know what else to check and i cannot afford to take it to a shop right now because loads are already killing me

please help!!

thank you

 

Forgot to mention.. no active codes besides the low coolant code when coolant level goes low on the reservoir

 

Can i get a 30 second lesson on how to check the EGR? Ive researched but everything is very vague on the topic

 

Also forgot to mention, on uphills loaded with 40k pounds and ac on i can smell the coolant and temperature climbs up to 210, fans kick in and temp lowers to 190 then it comes back to normal operating temperature (170-180). On steep downhills with no throttle usage it does the opposite ( goes down to 130-140) i checked the heater core and there are no leaks coming out of it. I also checked under the sleeper and everything is bone dry except for the ac lines when ac is on

 

Any ideas?

 

Early this morning after 15-20 minutes of the low coolant level warning, my truck stalled and died on me. thankfully, it did it right on my hometowns exit ramp and i was able to get someone to help me.