Danfoss Making Noise - Not Anymore!

My Danfoss valve is making a noise when it opens and closes (keeping return temp to the boiler at 140*) that sounds like the song of the killer whale. Since the thermostatic valve in the Danfoss is always self adjusting for the temp, it is nearly constant once the boiler reaches 150* or above.
It isn't really a problem because the boiler is in the garage, but I haven't read on here that others have the same problem. It seems to be working OK, but I wonder if it is recirculating too much water to the boiler as well based on the temp difference between the boiler output and the loop temp. I have a ball valve in series with the bypass - should I try throttling back the amount of hot supply water which can be circulated through the Danfoss back to the boiler? This would increase my loop temp but might drop my return temp below 140*

Any thoughts?

Thanks for the laugh. If my system was worth the millions that car is, maybe I would have the free time to figure out how to get it to play a tune. For now, it sounds like I am holding a pod of humpbacks hostage in my garage.

I should have clarified - I am referring specifically to the Danfoss TV valve used to control the temp of the boiler return.

I took the valve apart yesterday. There was a minimal amount of sediment in the housing, not enough to cause a problem. Boilerman, I was thinking the same thing once I got it apart. Although I installed the valve according to the instructions and the label, the valve appears to me to be installed backwards. The thermostat inside is similar to an automotive thermostat. It has a wide, flat disc with a spring on one side and a contoured "bulge" on the other side. The thermostatic element is surrounded by the spring and causes a pin to extend when heated. The pin pushes on the bulge, causing the disc ant the thermostatic element to move in the direction of the spring, compressing the spring.
As installed, the spring and thermostatic element is immersed in the cooler return water so the valve does not open until the entire valve housing heats up. Also, the disc has to move against the flow of water to operate so system flow is trying to force it closed. Also, unlike an auto thermostat, there are no holes in the disc to allow a small flow through the thermostat even when closed. These factors I think cause the "singing" and the pipe banging I am experiencing when the valve operates.

I don't know if I can turn the thermostat and its brass housing around in the valve, but I think I will try it. The difficult part is getting the system cooled down, and the two gallons of water lost when opening the housing. Even though I have an air separator at both high points of the system it takes me forever to get all of the air out again.

As an alternative, I can get a 113* element for the valve. I don't know if this would be too low, but when operating at full load I am only seeing a 35* drop from supply to return at the valve, so I don't think there is much danger of cold shock to the boiler. I also don't have make-up water feed in automatically, so no danger of that temp differential either.

An Update:

Last night I was able to confirm that the TV is indeed installed backwards. I was able to use my bypass valve and isolation valves to essentially reverse the flow of water through the valve and it operated normally.
The instruction sheet included with the valve (but not on the web) shows two installation options. "Typical Installation" follows the label on the valve itself. "Gravity/Large Volume" installation shows the valve in backwards to the label on the valve. Both installations require a balancing valve installed in the bypass pipe, which I have. This valve is adjusted to allow the least amount of flow through the Danfoss while still providing boiler return temps above 140*F.

I think what is happening in my case is that the valve is not opening until the housing heats enough to allow the valve to operate - typically about 155-160 on the gauge. When it does open, the disc is fighting the flow (8 gpm @ 17 ft head) causing the "singing". as soon as some of the cool return water hits the valve it closes, causing a pipe shudder that shakes the whole boiler, etc.

I am going to call Danfoss this morning to see whether I can just rotate the guts 180* inside the housing. When I had it apart before it looked possible. I do not want to tear apart the plumbing again.

I will post pics later today.

deleted double post

See below. In this configuration, the Danfoss is bypassed allowing full flow to the loop. Note diagram on label. My Danfoss came fully assembled.

Danfoss valve instruction sheet. I found it with other documentation after piping was complete. I only read it after I started having problems. Instructions? We don't need no stinking instructions!

My plan for tonight's teardown of the valve (if possible):

Current setup on the left, correct setup on the right.

Yes, you are right. The direction of port 2 does not change. It seems that in my valve, port 1 and 2 are reversed. I am going to try reversing it tonight and see how it performs.

Painless, but not dry...

I will report on my progress as it happens.

Well, I can report success turning the guts of the valve around. System was cool - 64*F when I got home. I took the cover off as before, removed the brass insert, thermostat and spring, got soaked, and installed the parts in the opposite direction. After refilling the system and getting out the air, I lit the EKO. If you notice in my pics the piping is all up near the ceiling. Within ten minutes of lighting, I had 110* water thermosiphoning through the piping - this has never happened before.
After half an hour, temp in the near boiler piping is 135* on the supply and return. Temp on the Danfoss return port is still about 70*F. At 140, the pump turns on and water starts circulating to the loop. Within two minutes, the loop is up to 115*F and the boiler has cooled to 135* - pump off again. Fifteen minutes later the whole system is up to 150*, so I start pulling heat from the coil in the house.
It has now been a few hours - the house is warm, the boiler is hot, and there is still wood left inside. I am amazed at the difference having that valve in the right way can make.

I hope my experience will help others who receive this valve already assembled. Check the orientation of the thermostat inside!
FYI, Danfoss did not return my phone call today. We'll see if they call back at all.

Update - because water is now flowing as it should, I still had live coals this morning after 7.5 hours burn, and the hous was still at set temp. I was able just to load again and was gasifying in under two minutes. Water temps above 150*F before loading. With this improvement in performance I am on target now for wood consumption.
Storage is the next challenge.