Monitor 41- Flame issues

[Grumpy]

I have a 41 that I just rebuilt the combustion chamber on. New burn pot and ring and new gaskets. Looks to be burning fine on low but when it ramps up to high I get a tall dancing flame from the front of the chamber. I have checked all the gaskets (new) at the ignitor and everything appears to be seated properly and no leakage. Don't remember seeing a flame like this before. It appears there is plenty of combustion air as the flame is laid over. Any thoughts??

[hawkins111]

Is there an air damper in your air hose? How old is the flue pipe?

[Grumpy]

I dont think there is a damper in the air hose. There is one in the combustion fan housing. I put new bearings on the combustion fan motor, replaced the o-ring that had come apart and was hung up in the spring. The damper plunger was working freely. The hose is in good shape and I can hear plunger when it first starts up. Earlier today I pulled the air intake hose off the fan housing and most all of the tall flame went away. I put the hose back on and it appears so Im thinking I may have some blockage in the intake pipe. Im not sure or the age of the flue pipe but it definitely has some age on it.

[hawkins111]

If you removed the air damper to replace the "O"Ring, I would start there. It is a little tricky to get adjusted.

[Grumpy]

Thanks Hawkins, I really appreciate your response. I know the damper can be adjusted by loosening the 2 screws at the rear and the damper can slide up or down. I seems to me that i need more air flow to calm this dancing flame down. Assuming that is correct which way would provide more air? Moving up or down?

[hawkins111]

You should see the glue spots for the two screws. I would start there. Because the flame gets better when you remove the air hose, I would look at the flue pipe very close. Old Monitor flue pipes can get corroded through on the exhaust side. If this happens you will get exhaust into the combustion air side and this will cause a bad flame. Be sure to use the proper air damper in the air hose.

[Grumpy]

I am going to pull the flue pipe out tomorrow and check it very close. It has a coating of soot in it now. I did see the damper in the air hose when I pulled it. Found a small pin hole in the air hose and is repairable. Will let you know what I find. Thanks again for your time and knowledge!

[Grumpy]

I decided to go back through everything to see if I could find something I missed or that didn't look right, It all looked good to me except the burn mat. After cleaning all the soot out I found the mat to still be glued down at all the corners but had raised up along the inside at the igniter shield. I decided to remove the mat and found a soot spot under it. Could this have been the source of the bad flame? What is the correct way to glue the mat down? I have always put a small amount of adhesive at each corner, placed the mat and pushed it into the adhesive and then added more adhesive over the corners. Should I do more?

[hawkins111]

Are you using a Monitor burner mat or another material? I don't have the numbers anymore but you can get material that is too thick and it will turn up around the edge. I have always used a torch on the material before gluing it down. This will burn off any chemicals on the mat. Put a thin layer under the whole mat and a blob at the corners on top and overhanging the edge of the mat. It takes a while to dry the thick spots ( 8 hours). I'll get you a material thickness in a short bit.

[Grumpy]

i have 1 factory burn mat left but have thought I would look for something from McMaster-Carr to be more economical. I was wondering about gluing under the entire mat. I have heard some say not to do it because if the glue comes through the weave the fuel will puddle and not burn clean. The last factory installed mat that I replaced appeared to have a thin layer of glue under the entire mat. Seems like if you keep it thin there wouldn't be an issue. I will give it a try.

[FordMan59]

Last two times I replaced the burn mat in my 422 I used McMaster-Carr material. First time I only glued (Rutland 77) where the Monitor diagram showed and when I took the burn chamber out trying to solve another problem I found the mat was lifted and curling after about 6 years. Second time I put a thin layer of glue (Rutland 77) underneath the whole mat. I think it's been in service now about 2 years without any problems. The McMaster-Carr material I've been using for my mats is 8799K3 and it works OK in the 422 but, you have to handle it quite easily after cutting or it tends to ravel around the cut edges. If I ever need more burn mat material I'm probably going to try a different product because of the raveling issue. The material I use for making gaskets I really like. It's McMaster product number 9323K21 and is much stronger than the original Monitor gasket material but like the Monitor gasket material it does get brittle and comes apart after it's been exposed to heat thus still needing to replace gaskets most of the time when disassembled. This material is 1/8" thick and seems to be thick enough in most applications. The only place I think I've ever had to double it up was on the igniter gasket.