L4701 chirping screeching

[FossilFuelPhil]

131 hours on 2016 L4701 HST.
Oil fine, Hyd. fluid fine, coolant clean and filled. Air and fuel filters clean.

Mowed for 6 hours one day and put tractor away, Started it up next day and it was loud chirping/screech at 1600 rpm and through power band, but goes away at full PTO 2500 RPM. I think its coming from water pump or alternator bearing. I think if it was the main it would be significantly more concerning in other ways.

Doesn't chirp at idle, or is not noticeable

Anyone have history with early water pump bearing failure? Its not leaking, just annoying.
I checked belt tension, and its spot on. Only thing I haven't done yet is remove the belt, start it, run briefly and see if noise goes away to narrow down the source.

https://www.youtube.com/watch?v=fMmfADUpwns


Any ideas?

 

[Dave_eng]

Remove belt and turn alternator and water pump by hand to see if you detect any roughness.

Start without belt but briefly.

Dave

 

[Bark]

Hope you get it narrowed down. That is pretty low hours for things to be going bad.

 

[SidecarFlip]

Belt could be loose as well.

 

[FossilFuelPhil]

Removed belt, alternator free and clear and smooth. Water Pump free and clear and smooth and sounded like a kitten meow when I spun it. Started tractor for 10 seconds through RPM range. Noise still there although slightly less pronounced, although it was a cold start and not warmed up. Just wondering if its the main. The noise is definitely coming from the crank/oil pan area. Oil is full, clear. not even sooty and was changed along with filter at 49 hours after break-in period.

 

[Tornado]

Removed belt, alternator free and clear and smooth. Water Pump free and clear and smooth and sounded like a kitten meow when I spun it. Started tractor for 10 seconds through RPM range. Noise still there although slightly less pronounced, although it was a cold start and not warmed up. Just wondering if its the main. The noise is definitely coming from the crank/oil pan area. Oil is full, clear. not even sooty and was changed along with filter at 49 hours after break-in period.

From 49 to 131 hours on the oil and its still clear and has no soot? Never heard of that.

 

[Bark]

I know very little about these things but if my truck was making noises that I thought might be main bearings I would get the dealer involved if it is still under warranty since that is some major stuff. If not under warranty, after making sure I had oil pressure, I would drain the oil inspecting it for any metal shavings and cut the oil filter in half to inspect the filter media looking for any metal.

I know it sounds like the chirping is coming from the crank/oil pan area but does it still make the noise when your HST is in neutral?

 

[Dave_eng]

I think it is time to let it sit and involve a dealer. If the noise is something expensive you don't want to make it worse.

Dave

 

[FossilFuelPhil]

I added a short video to my original post. I'll go to the service dept at the dealer and discuss first before I tow it the 50 miles to get it there.

 

[Dave_eng]

One trick that can help narrow down where the noise is originating is to use a length of plastic or rubber hose. 1/4" to 3/8".

Hold one end in your ear and the other move towards the noise you are trying to locate.

I have learned it is best to attach the end of the hose or tube to a dowel or stick to keep your fingers back from where you are going to place the end of the tube while searching for the noise.

Dave

 

[Pau7220]

Try to narrow it down with a hose like Dave said. Check the exhaust for leaks also.

 

[FossilFuelPhil]

I think I am getting it narrowed down. The noise is definitely coming directly out of the exhaust pipe. I suspect that its possible an air powered whistle coming out of the DPF. Maybe there was an incomplete regen, maybe the mesh has particles on it still and the whistle is just compressed exhaust gas passing over the internal components. Kind of like when you turn your shop air compressor tank valve to release pressure and little chunks of internal rust or crud pass through with similar noises.

I've never really had many regens on this tractor. Most of the work is done at 1600-2400 rpm. I can occasionally tell it might be regenerating when mowing because there is noticeably more heat coming from the deck that at other times.
Hopefully its not a bad DPF unit, but I'll keep an eye on the guages, fluids and noises.

During my inspection I decided to check the front axle fluid. I loosened the check bolt and a lot of air came out. I started adding fluid and it took 2.25 quarts. There is no evidence of leaks anywhere, as also evidenced by the the fact that there was pressurized air in it.. Maybe it was an airlock situation when they "filled" it. 4WD works fine and no grinding, hopefully no damage done from only being 1/2 full.

 

[Yooper]

I think your theory is right on the money. When I worked for a trucking company as a mechanic there was a batch of tractors that had perforated screen in the exhaust pipe for sound attenuation. On Just a few they would whistle at certain rpms. Replace it with a straight pipe and problem solved. I wonder if lightly tapping on the exhaust parts when it is doing its thing might help you isolate what part is causing it. Maybe a scope camera if you know someone who has one. Good luck and let us know

 

[WHW]

Glad you seem have narrowed it down. My 4701 with with less than 10 hours started doing very similar. Shut it down and opened up the hood and started going through all of the things I thought could make the noise. Found that the fan belt was not in its groove....

 

[FossilFuelPhil]

Update: 19 engine hours later. Chirping/ screeching varied through all rpm levels over time. Fluids, temps, oils, all normal. Dissipated quite a bit after a regen. I'm thinking it may have just been a chunk of particulate or who knows.. maybe a mud dauber nest in exhaust that finally blew out. My usage is typically once a week, and while enclosed in a metal building, no telling what happens in the hours between.

Its just extraordinary though, I now have like 100 hours on my engine oil and its really not dirty or black, just a nice clear caramel like I just poured it.
My Ford 6.7 powerstroke is black as coal in 5 miles when I change it. Maybe the DPF is just really quite efficient, or my oil is getting diluted from the fuel injection during the regen, but level is always spot on.

 

[Dave_eng]

Update: 19 engine hours later. Chirping/ screeching varied through all rpm levels over time. Fluids, temps, oils, all normal. Dissipated quite a bit after a regen. I'm thinking it may have just been a chunk of particulate or who knows.. maybe a mud dauber nest in exhaust that finally blew out. My usage is typically once a week, and while enclosed in a metal building, no telling what happens in the hours between.

Its just extraordinary though, I now have like 100 hours on my engine oil and its really not dirty or black, just a nice clear caramel like I just poured it.
My Ford 6.7 powerstroke is black as coal in 5 miles when I change it. Maybe the DPF is just really quite efficient, or my oil is getting diluted from the fuel injection during the regen, but level is always spot on.

Thanks for the update. Glad the solution was so simple but it sure did not sound like it.

Dave

 

[FossilFuelPhil]

30 hours later, normal sounds just like when it was new through all rpm ranges.
After 4 years, I drained fuel bowl and cleaned everything , but never any water.
I'm just puzzled about the clearness of my engine oil... Its just so clean and barely grey on a white rag when I check it regularly, and after 100 hours of run time, right on the level, never fluctuates. Are these engines running that clean? I get that sour DPF smell on idle occasionally, like my Powerstroke 6.7, but these motors don't use DEF, so kind of funny
Regens are never dirty or sooty , just a little warm under the floorboard when no wind and I've only ever had to initiate one one time just by running high RPM for 15 minutes to make the early blink light go out.
I guess I should just be happy and keep on keepin on.