I'm hoping folks can give me some feedback on whether to be concerned, take any pre-emptive action, or just chill.
I have a 2014 OM651 with 82k miles, original owner. I've had intermittent "low coolant" indicator light issues since December 2017 @ ~ 45k miles. It began during an extremely cold period when I was driving through Iowa (like -30F overnight cold). The light would immediately clear after I stopped and restarted the engine. As I made my way to warmer climates, the light stayed off. Until summer . . . then it would come on every 10 starts or so, but immediately clear on subsequent stop/start. It continued that way for another year. Coolant level on overflow reservoir didn't seem to visually change during that time, it was always above min and just below the seam in middle of reservoir.
With this as the background, I had the van in for scheduled maintenance (transmission fluid, brake flush, etc) at Lynwood MB north of Seattle in April 2019 @ 60k miles. I specifically mentioned these coolant light issues and they investigated. Told me they found no issues or evidence of a problem. I assume this means that there were no coolant related codes in the history. I'm confident that the mechanic was competent and honest on this issue, since he also found a small wallet w/ $300 in it that I had lost a year earlier (trapped in cavity that got exposed when he did airbag recall work) and he returned it w/ all the cash
.
Then in December 2019 I took it to a dealer here in Tucson, 10 days before my 5 year warranty expired, to get a "check up", hoping that would establish a warranty period timing on any still-developing problems if any codes were found. To my disappointment, the service writer wouldn't do anything without me signing off on a $500 charge pre-approval. I was like "look, this has been a problem for 2 years, doesn't that justify looking at it?" He claimed it was irrelevant to warranty because "cooling system isn't the engine, that warranty passed." I was like "you're seriously telling me that the water pump isn't part of the engine?" I got frustrated. They wanted ~$200 minimum for an "inspection" (one hour service minimum maybe??). I ended up leaving without any service or diagnosis, fairly pissed off. Very different experience than the Lynwood dealer.
ANYWAY, to make a short story long, after that dealer fiasco, I got myself some compatible coolant. mixed it 50/50 with distilled water, and added one pint of 50/50 to the reservoir back in January 2020. I never saw the coolant light again. Until today. It lit up on first start, went away on second start. I checked coolant, and its definitely below the level I filled to in January 2020, maybe 8-16 ounces less.
The good news is that I haven't had any CEL lights this entire time. (I assume when people here are saying CEL and code P261F, they mean that there was the "general" CEL light and a scan showed P261F? NOT the the coolant icon light?).
I don't have a scanner. Can I assume that the engine has never thrown a P261F or P0128, if I've never had a CEL?
Any suggestions on the sequence of inspections I should do to try and determine if my coolant loss is related to the coolant in vacuum system? Or a more benign leak/problem? I'm willing to acquire a scanner if helpful (although dreading the 2 day rathole reviewing threads here to select my preferred scanner!!).