Troubleshooting Low Coolant Level Warning Message

[Longhorn81]

60 days ago my local Newmar dealer addressed a low coolant level warning issue by replacing my transmission oil cooler. The dealer said they saw evidence of a leak however there was never any kind of evidence of a leak on the ground at my storage unit coming from the rear of the chassis (Freightliner).
Yesterday, during an exercise session and fuel fill, I briefly got another low coolant message and the yellow MIL light came on and stayed on. I don't know how to access the code(s) that would tell me the MIL light is related to the low coolant message however it seems highly likely.
When I got back to my storage unit I noticed a spot on the ground more or less under the front driver side jack. The spot, which is about the size of a trash can lid, is a dark rust color and is not at all wet to the touch. I noticed the spot in the past but always thought it was there when I rented the space. Now it appears to be slightly larger as if there might be a small/slight leak that moves around as I park in slightly different locations.
I crawled under the RV and took pictures in hopes of identifying where a leak might be coming from. Please see pic below. I found no evidence of dripping although as shown in the pic there appears to be a rusty hose/pipe of some kind that could be the source. Can anybody identify this hose/pipe and help me determine if it is carrying coolant? At the point where this pic was taken the hose/pipe runs side to side (as opposed to front to back). All thoughts, comments, guesses welcomed. Sorry about the long post! TIA.

[MikeyG]

John:
I had the low coolant warning and MIL lights two years ago. Plenty of coolant in the tank as verified through the sight glass and nothing on the ground indicating any sort of leak. Turned out it was a sending unit in the coolant tank that went bad. Had to drain most of the coolant, replace the sending unit, and refill the tank. Done under warranty at FL.
Hope your issue is that easy.
Good luck,
Mike

[Toribk]

Yes....if you have a coolant reservoir, check to make certain the fluid level in the reservoir is at the normal "Cold" mark usually embossed on the tank.

When it falls below that, the amber MIL will illuminate on the dash. As mentioned previously, if the level is normal....you could have a bad sensor at the reservoir.

I included photos of my old sensor (leaking) and the new one I installed just for reference on my Freightliner XC Chassis.

Any dark liquid found around the bottom of a jack leg COULD be a slight hydraulic leak.

Let us know when you find out.

[Dutch Star Don]

A couple of things.....that transmission coolant tank in 2019 was known to leak. There are some welded bungs on the upper side of the tank that leaked, but typically blew off before they dripped. I had mine replaced and know of several others that were replaced. They are Chinese made.

Second, the first year we owned our 2019 DS, the tank level sensor glitched, threw a code, but cleared when we pulled into a Cummins shop for replacement. It was replaced anyway. With that said, sometimes when they install that new tank, they may not have gotten all the air out and your coolant tank could be low. Read your Manual and it will tell you how to access the codes via the dash, then call Freightliner and they'll tell you what they mean.

Lastly, if you have lead acid batteries, my guess would be that you're dripping battery acid where that spot behind the left front wheel. The coolant lines are run in the frame rail on the passenger side.

[Longhorn81]

Thanks for the responses guys. They give me a few things to look into. Oh, and Don, I think my new trans cooler was made near Ft. Knox (given the price). I'll post my findings once I know more.