Gents, I haven't started putting in all the "fix" attempts on my 5500 yet as I am wanting to do the roller mod on the wonky kitchen slideout first...before I have more damage. But the Onan is next, for sure. Haven't needed the Onan in hot weather
yet, but I know the overheating problem awaits.
I ordered my cooling air intake plenum from Jayco about 10 days ago and they said it would take about 4 to 6 weeks to get it here. I also ordered the Onan Cooling Air (Exhaust-side) Deflector from Cummins a few days ago and it came today. Two styles of the Cummins deflector are shown in their TSB:
https://static.nhtsa.gov/odi/tsbs/20...02376-9999.pdf I believe the combination of the intake plenum and this deflector is supposed to alleviate recirculation from the exhaust side of the Onan's cooling flow path back into its intake as they are side by side (whereas the intake plenum's function is to duct air in from the side of the coach, rather than underneath.) Has anyone out there installed the Cummins Exhaust Air Deflector when they installed the inlet plenum/scoop? I'm "thinkin'" that the inlet plenum is the major player and the exhaust deflector is mainly to prevent the Onan's cooling air "short circuit" under there when the coach is stationary. Since it was only $63 from Cummins (surprised it wasn't $363) I decided to put it on. Can't hurt as they say.
From the many posts I have read here and on the FaceBook
Precept and Alante forums the two main contributors are cooling air flow and vapor lock/fuel boiling in the carburetor bowl. I plan to attack the latter while I wait for my "scoop" kit from Jayco (with lots of fuel line insulation all the way to the carb and lots of closed-cell foam tape insulation around the carb bowl area.)
All the info from the forum is much appreciated. If I stumble onto something that works I'll sure share it. Best ......... Ed S.