Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 14, 2025 ...

Mark,

Here are some random thoughts in no real order of importance. In that area there is limited place that the oil could come from. There is an area where the hoses are not covered in that same area where you could have a chaffed hose.
 Have you been able to detect a loss of oil in the hyd. oil tank? 
 It could also be oil from the A/C hoses that run along the same chase. If it was one of those hoses you would know pretty quick as your dash A/C would have quit. 
Have you thought about a diesel fuel leak?  It could be diesel from the return line.
It isn't likely to be the differential oil but...  Did you have synthetic oil installed in the  differential?  If so it can seem pretty thin. Have you checked the  differential to see if they overfilled it?  The differential breather hose terminates in that same area on our coach so look for the end of it. 

Smell it. Motor oil (hydraulic fluid), gear lube and diesel smell VERY different.

Could be a chaffed hose.  I need to look further.  I was pretty focused on the AF1 install so I tabled this new development until I complete the AF1.  I'll check the hydraulic tank today.  I changed the hydraulic oil and filters also about 1 month ago so it should be full.  Unfortunately the dash AC hasn't worked since I bought the coach.  The differential oil is dino, not synthetic.  The differential breather tube is something with which I'm not familiar.  I'll look for that.

Diesel is a possibility I hadn't considered.  The consistency of the fluid residue seems to be closer to diesel than to 80/90 weight. There was a drop of the mystery fluid on the bottom of the wet tank and also a drop of 80/90 on the bottom of the differential drain plug.  I compared the two yesterday.  The differential fluid was more viscous and darker.  The mystery fluid was lighter in color and much less viscous.  I'm recall thinking it had a greenish tint although I didn't think of diesel at the time. I didn't notice an obvious odor like that of diesel.

Thanks for the suggestions!

"Greenish tint" might indicate AquaHot boiler fluid.?

Depending on build number, 2003 and newer (that was the changeover year, IIRC), the AquaHot should have pink/red GRAS boiler fluid in it, not the green that early 2003 and earlier coaches had.  Has to do with the specific AquaHot design.

6106 was built with the newer AH design.  I would expect Mark's 6199 would be, too.  I'd be surprised if your 6160 wasn't as well (but run your AquaHot serial numbers past Rudy to be sure).

ETA - here is some info regarding the s/n of the AH and what fluid What Fluid Should Be Used In Aqua-Hot Coolant?

(and from what I've read, even though Century brand boiler fluid is GRAS and yellow/green, I would stay away from it)

The AquaHot unit in our coach was replaced by the PO a few years ago. It has the green Century heat transfer fluid in it.
I was not sure of what fluids were approved so I went to the AquaHot web site to find what they recommend. Seems that the pink Camco or the green Century fluids are OK with them.

"Greenish tint" might indicate AquaHot boiler fluid.?

If it were me I would probably just clean everything off, verify all fluid levels, take the coach for a drive and see what shows up. Hopefully it will become apparent where the fluid is coming from, or better yet, there won't be any leak.