2004 Fleetwood Flair 8.1 engine fan noise

[garymunson]

I thought I'd post my strategy for taming the fan noise on my 2004 Fleetwood Flair. My coach has a 'hatch' in the middle of the engine doghouse. Removing it and looking inside made it clear the doghouse was molded fiberglass with the only sound deadening the carpet glued to it. My doghouse was glued and screwed down to the coach floor. The carpet was 'reversed stapled' to a tack strip that encircled 3 sides of the doghouse. After peeling the carpet back, I was able to remove the screws and tack strip, then, driving assorted putty knives between the floor and doghouse, was able to cut through the sealant and free the doghouse. I discovered the top and side edges at the front of the doghouse had no screws securing it, relying on a bead of sealer to close the gap, helped by the doghouse screws pulling the entire assembly down. In my case, the sealant had separated from the doghouse in several spots along the top and sides making the noise worse. I cleaned the inside surface of the doghouse with Simple Green then I used one of the sound deadening materials sold by Summit Racing. Probably any of the Dynamat-like self-sticking foil-faced rubbery products would work. I covered the entire inside surface of the doghouse with this and then used a 'camper shell' weather stripping from Home Depot as a gasket around the entire doghouse perimeter. I used clear silicone sealer at the front lower corners as there were some gaps as I re-installed the doghouse with self-drilling screws. Before replacing it, I also changed to a 180 degree thermostat from O'Reillys Auto Parts in the hopes of lessening the times the fan engaged. Once done, I found the engine noise greatly reduced and switching thermostats made a considerable difference in the frequency of the fan clutch from engaging. Using my scan tool, I was able to determine that the engine runs about 10 degrees cooler most of the time (not a lot, but enough to lessen the fan engagement). The project consumed most of a day but it's sure easier to talk in the cab now!

[rgatijnet1]

You may not throw any engine codes but if your AF ratio is not at 14.7, after the engine has reached operating temperature and you are at a normal level cruise, you just may be running a little too rich. Besides impacting your fuel mileage some, it may also cause your plugs to foul sooner and may eventually affect your catalytic converter. This is an easy thing to check with any scan tool rather than to guess as to what is happening with your engine.

[Gjac]

I did not think that 15 degrees would make a difference either but it did. Like I said mine was a 454 maybe the 8.1 is different.

[garymunson]

From what I can understand looking in the programming tables for an 8.1, it looks like 175 degrees seems to be considered 'full operating temperature' so I can't see where going to a 180 thermostat will make any difference in mixture control. I've seen quite a few posts where people have done that without any issues with smog checks which is the only other problem I could see. We all get such horrendous mileage I really don't think anyone would notice a change with that. Since a 180 shouldn't open until it reaches 180, the engine should not run any cooler than that even in the winter. I'll see what happens when it cools down but I can't think of any reason a code would be set just because of a 15 degree lower tstat.

[Gjac]

When I first got my MH a 454 TBI it ran hot and I added an extra layer if insulation to the doghouse and an 180 thermostat. The insulation really kept the heat and noise down and the 180 degree thermostat reduce the engine temps also but created other problems that took me a year to figure out with the help of some on this forum. What I noticed is that I started throwing engine codes every so often. Then noticed a pattern toward the fall. When I went back to a 195 thermostat the codes went away. 180 seemed fine for summer heat but not when temps dropped. What I evolved to was adding 2 #40 holes in the flange of the 195 stat to allow more cooling water to flow by. They also sell a HD stat with a poppet in the flange to allow extra water to flow by. With this mod and headers I don't hear my fan clutch come on at all except on long hills.

[Altern]

rgatijnet1 wrote:
Take your scan gauge and see if your Air fuel ratio is still 14.7 at normal cruise.
If it is not, it is because your engine is running too cool and the computer is enriching the mixture as if the engine still had not warmed up.
If your AF ratio has gotten to 14.7 then all is good. If not, your engine will be running too rich and burning extra fuel. In the old days, to some extend cooler was better. Now with computer controlled engines, and change in one parameter is met with an automatic change in something else.
You may also want to check your firewall for any open spaces which will also let noise in to the cockpit.

Understanding stoichiometric values. HERE

[rgatijnet1]

Take your scan gauge and see if your Air fuel ratio is still 14.7 at normal cruise.
If it is not, it is because your engine is running too cool and the computer is enriching the mixture as if the engine still had not warmed up.
If your AF ratio has gotten to 14.7 then all is good. If not, your engine will be running too rich and burning extra fuel. In the old days, to some extend cooler was better. Now with computer controlled engines, and change in one parameter is met with an automatic change in something else.
You may also want to check your firewall for any open spaces which will also let noise in to the cockpit.