Roaring noise at 30-40mph

[wrightsw]

New to the forum and to motorhome ownership. Bought an older one and am fixing it up. I have noticed that it makes a noise between 28-38 mph. It's a low pitched, loud, reverberating roar that seems to come from the front of the coach. It goes away by 40 mph. Doesn't seem to be related to road surface quality and there isn't a vibration with it. Could it be from the engine intake? The grill? Anyone heard this?

[Gordon Dewald]

Could it be the engine fan?

[wrightsw]

Doesn't seem to be. It's definitely speed related, but it doesn't seem to be temperature related. The coach is pretty quiet and it definitely goes away right around 38-40 mph.

[Gordon Dewald]

Does it change with engine rpm at the shifts? I still am leaning towards the fan clutch.

[TeJay]

About the only thing that makes that kind of noise is the temperature controlled cooling fan as Gordon mentioned. It's very possible because of the speed, kind of slow, not enough air is going past the fan at that speed so the clutch engages the fan so more air is drawn through the radiator cooling things down a bit.

This will usually happen about 1/2 way up a hill or just as you crest. You are going the slowest and the engine temps are rising some. The fan does as it's supposed to do. I'm not saying that it's not something else but your description describes it to a T.

The reason it goes away at 40 is because the air has cooled things off and the clutch disengages.

We have a 2014 F-53 engine and I have never heard the fan engage. I guess they've improved them so much that you can't here them at all. I know when I drove a school bus you sure could hear it every time you climbed a hill.

TeJay

[wrightsw]

Great ideas, but it doesn't change pitch with engine shifting and I haven't been on a trip yet that includes a hill. This occurs just tootling around town. The weather has been nice too, not hot, maybe high 70's. It happens whenever I hit the speed range even just out of the driveway before it could even really heat to operating temp, let alone be hot.

[Gordon Dewald]

Sorry I am out of thoughts on this. Our 450 will make a roaring sound but it definitely is the fan cutting in. First time it startled the stuffings out of me.

Will need someone with more epertise than me to diagnose this issue.

[wrightsw]

Thanks a bunch, maybe it will turn out to be the fan, time will tell.

[Gordon Dewald]

If you can reach in and see if you can turn the fan by hand. It should turn freely with a little resistance. Some folks in the day replaced the fan and clutch with a plastic fan that was supposed to deflect at speed by twisting.

[wrightsw]

Will head down to the storage lot tomorrow and give it a try.

[glen42]

I had a bounder that the grill had hollow tubes horizontally across it. It made a noise just like you are talking about and at the same speeds. I plugged the ends with silicone and the noise went away.

[jondrew]

Have you looked behind the grill? Perhaps there is a lion in there. See if he answers to Cecil.

[wrightsw]

That's what it sounds like!! A huge base flute or someone blowing across a massive bottle. My old Brave has a flat front with square cross tubes and rectangular grill openings. I'll have to try partially blocking the grill off and see if it changes the sound.

[sdlowe11]

How about getting up to speed, put it in neutral, shut off the engine and coast for a few moments. That will eliminate anything involving the fan, engine and transmission. It's a bit unnerving to do it, but if you're in a place where other folks aren't around it should be safe. I used to do it in cars to isolate noises all the time (and sometimes heard new noises without the engine running ).
Good luck!

[Duner]

Originally Posted by sdlowe11

How about getting up to speed, put it in neutral, shut off the engine and coast for a few moments. That will eliminate anything involving the fan, engine and transmission. It's a bit unnerving to do it, but if you're in a place where other folks aren't around it should be safe. I used to do it in cars to isolate noises all the time (and sometimes heard new noises without the engine running ).
Good luck!

Agree with Steve, all you have to do is change engine rpm when you hit 38-40 mph. Just put in neutral, or 2nd or 3rd and not "D"rive. No need to turn off the engine, just let idle down while at the speed where you hear the sound. If it goes away, it's probably a resonating frequency of the fan.

Also try with a/c on to see if it's the compressor clutch/bearings. Probably not the issue but easy to test for.

Happy Trails,
Bill

[dieharder]

If noise doesn't go away with the procedure described above, your description reminds me of an old Mustang I used to have that would do the same thing. It was the universal joint in the drive shaft.

[wrightsw]

Good ideas, all. Now I have a list of tests.

[Piddlerman]

I am looking at a 2007 Winnebago Journey 34H Journey with a Cat Diesel. Only 16,000 miles, one owner. Have these been good coaches. Any advice on things to look for? Thank you!

[Eyephoto]

I have a door awning that was causing a howling. I filled it with a piece of 1/2" pipe insulation. Hope you find your noise.

[IdahoSRT10]

Originally Posted by dieharder

If noise doesn't go away with the procedure described above, your description reminds me of an old Mustang I used to have that would do the same thing. It was the universal joint in the drive shaft.

That's the direction I am thinking also. Maybe a broken, loose, worn motor mount. Under acceleration torque can make failed motor mount vibrate.