I'm happy to see that someone else has had a smell problem with their Sunline. I purchased mine, an '01 2753 in August '03 and have had some level of stench since I brought it home. Now, it's not too bad, but still some there.
The first odor wasn't hard to find. The original odor was toilet. Since the guy I bought it from was a bachelor, he was using it as his 2nd home and it had been parked since purchased in his brothers driveway and had no more the 500 miles on it. The toilet effluent was pumped directly into the home's septic system by some dinky little grinder pump. The system was supposed to have been drained and flushed before I picked it up and I didn't check it out - it was FULL and a 100 mile trip home sloshed a lot that "crap" up into the toilet itself. The tank itself was solid **** and I ended up making a spray wand to clean it out. I spent hours cleaning and carrying 5 gallon buckets to my home toilet but ended up the following spring replacing the toilet because the smell never went away - and with a hand operated unit instead. A note here - the hand operated toilet for a center bath works nicely as the foot pedals are no longer a tripping hazard.
Now we have another smell - we have cleaned, shampooed, disassembled what I thought was about everything - now I have some more 'ammunition' to further my search.
'01 Sunline Solaris 2753
(Now a Sunline Alumnus)
With an '06 Glendale Titanium 28E33TS fiver
'06 F350 V10 Lariat 4x4 CrewCab