Noisy Onan 4K = hack job install?

thats a totally enclosed unit
in the bottom of that picture, it looks like rubber mounts for the motor
it is possible they are too tight

you could put in a new piece of flooring, say a piece of 5/8 plywood with a hole cut for the exhaust, maybe some metal flashing/heat insulation
an set the whole genset enclosure on new mounts

look up the mounting instructions for that model
should be easy to find the PDF file, should also be in your generator manual that came with the install

Cummins Onan QG manual

from the pictures, it looks like internal springs between the power section and the enclosure floor

that looks horrid, expect those screws to break on the first big pothole. was this a factory install?

IMO, a total hack job of installing the genny. The Onan MicroQuiet genny unit has isolation mounts that are internal to the housing so you are good there. (you can see them in your second photo) On my class A Fleetwood, the Onan 4000 genny sits in its own basement compartment mounted on a tray made of square steel tubing. The entire compartment is completely open on the bottom to let the hot air/noise/vibration out. I suspect that is part of your noise/vibration/harshness issue.

Adding some sound insulation to your compartment, opening up the bottom, then mounting the genny unit on some steel channels which mount to the sides of the compartment with additional rubber mounts between the genny housing and the tray may help. (if you have the vertical space) Don't know about the construction of the sides of your compartment but the genny weighs about 172 lbs. so they have to be strong enough to support the load. Go look at a class A MH to see how they do it. Think engine compartment in a car/truck. In most modern vehicles you can't even hear the engine when done properly. (unless at higher rpms/loads)

As a side note, if you like doing your own maintenance, I suggest you remove those silly torx screws (2) that secure the green cover (second picture) that provides access to the oil drain plug. Replace them with standard 5.5 mm internal hex or 10 mm external hex grade 8.8 metric machine screws. Then, in the future, you wont need special tools just to change the oil.


Chum lee

LittleBill wrote:
that looks horrid, expect those screws to break on the first big pothole. was this a factory install?

I would be concerned about the whole unit breaking through the floor when he hits a bump.

Yes factory installed by Eclipse RV:(. No it wont fall through the floor. There are frame rails that run along each sides that would prevent however I don't understand why they did such a large cutout on the bottom. All the hot air exists around the area of the exhaust. My brother just bought a trailer from another manufacturer with the same genny and I am going to see how it was installed and how loud it is next week.

One thing I have seen looking at some videos online is many with the same generator do not have a cutout on the trailer access door like mine (see top of first pic). Is it OK to block that off as that is where most of my noise is coming from the area of the fan.

N-Trouble: The hole in your compartment door is for combustion/cooling air and you can't block that off. If you do, you risk damaging the genny from overheating it. (warranty void!) If the compartment is otherwise sealed well you may not get enough combustion air either. That's why most genny installations inhale and exhale out the bottom or the side if mounted in the rear basement compartments!

Chum lee

That is what I thought as well just surprised to see many access doors with no cutout/venting on them.

Do you have room to add a steel for the genny to sit on? With clearance for frame and more, you could set the frame on rubber mounts AND out rubber mounts between frame and genny. Might have to extend exhaust.

You are not going to be able to quiet it a lot but lining the inside with some material like this will help.

The noise coming from the bottom intake and exhaust is difficult to deal with. If you are parked, hanging a moving blanket along the side will do an amazing job at blocking the noise in that direction.

sound deadening material

Normal install. Mine also had a large cut out below. Not sure about vibration or cause if it is excessive.