5 year burn chamber rebuild update

[FordMan59]

The reason for this thread is for people who are looking for cheaper/easier to find alternatives to MPI products and want to know how well they last. I used cheaper products, thanks to HayZee518 for this information. Lots of people on this forum have used cheaper alternative products in their chamber rebuild, but no one I know of has reviewed them after several years service. I rebuilt the burn chamber in my Monitor 422 5 years ago this month. I used a new MPI flame ring, McMaster-Carr product 8799K3 for the burn mat, McMaster-Carr product 9323K21 for gaskets and Rutland 77 stove cement for gluing the mat. The McMaster-Carr 8323K21 material is much stronger and less brittle than the original MPI gasket material. After 5 years of service I still have a nice even blue flame and no signs of problems. There are other McMaster-Carr products that will probably work just as good, you'll just have to decide for yourself which one you want to use. At the time I did the rebuild a new flame ring, more of each McMaster-Carr product and Rutland stove cement than I'll use in my lifetime cost less than $100. Next time I need to do a rebuild the only cost associated with it if the pot is still good should be a new flame ring. I'm in a warmer area of the country than many using Monitor heaters, so my heater doesn't run as much. The original flame ring, burn mat, and gaskets lasted 16 years on my 422 and I probably average using about 125 gallons of kerosene per winter. My 422 is now over 21 years old and still running great. The only parts I've replaced on it are the parts for the burn chamber rebuild and a new time/temperature controller. Some of the buttons on the original controller got so they didn't work very good. Thanks to another member of the forum I was able to replace the controller with a new one for $100., which was less than the cost of getting the old one rebuilt. I still have the old one in case I ever need to have it rebuilt for future use. For the past 6.5 years since moving to our new home I've been using capsule tanks and recently started having problems with the fuel not wanting to feed to the oil reservoir. I took the filter beneath the capsule tank out and soaked it a few hours in vinegar (mild acid) and it's doing great again. Thought I'd add this information in case anyone else ever has a similar problem. Carburetor cleaner or a similar item would probably work fine too, but I didn't know what effect it might have on the plastic or the filter media.

[hawkins111]

Thanks FordMan for the McMasters numbers. They will help others out in the future.

Tom Hawkins

[FordMan59]

Thought I'd update this thread. The heater was giving problems so I took it apart today, the burn mat was brittle, lifting and curling up so it was replaced about 1 month short of 6 years. This was a burn mat made with McMaster-Carr product number 8799K3 and glued down with Rutland 77 stove cement. As I said earlier in this thread the gasket material McMaster-Carr product number 9323K21 is stronger than Monitor brand gaskets but it does get soft and brittle when exposed to heat. I replaced all 4 disturbed gaskets. The gaskets were fine until I took it apart but at that time they started falling apart kind of like the Monitor gaskets do. If I'd bought Monitor parts and glue the cost would have been about $100. instead I used supplies left over from the materials I bought in 2012 and still have enough of both materials to last the rest of my life. There's still enough Rutland 77 cement to do the mat probably 3-4 more times. Took about 30 minutes to mark/cut the mat and gaskets so unless your time is worth a lot more than mine it's well worth the savings.

[handyandy]

Thanks for the update FordMan

[FordMan59]

Glad to give the update. I have no doubt the mat would have lasted longer if I hadn't disturbed it removing carbon build at the fuel inlet. While I was there I went ahead and replaced the mat and gaskets hoping I won't have to tear into it for at least another 5 years.

[FordMan59]

I just put this heater back in service 1/17/19 with a new mat and having the flame ring welded all the way around. The heater had been out of service for the last year since I installed the new mat. If/when I have to remove the chamber again I'll give another update on how the mat/gaskets/flame ring are holding up. This ring had already been in service 6 years when I got it welded and reinstalled.

[rrob311]

I am interested on how you had the ring welded. Did you remove any material or add any?

[FordMan59]

I am interested on how you had the ring welded. Did you remove any material or add any?

I just had them leave the existing welds where the dome of the flame ring is welded to the bottom portion of the ring and had them continue the weld from one weld to the next until the dome was welded all around the circumference. I also had them hit the clips that hold the ring in the pot so that it won't be as likely to come loose. Once everything was welded I had them take a grinder and grind the new welds down to the same elevation as the original welds so I'd be sure they didn't make contact with the flame rod. The ring has been back in service now for about 4 days and no problems.

[hawkins111]

In the last years of my stove business I would use burner mat cement to make the seam on the M422 burner ring smooth. I did have some success with that idea. The rings would last for quit a while before mushrooming out and causing a bad flame. One thing I did have to do was drill a hole in the top on the ring to relieve any pressure build up due to a sealed top piece on the ring. If there is a problem you will notice the flame moving around. If there is a problem it is very noticeable.

[FordMan59]

I the last years of my stove business I would use burner mat cement to make the seam on the M422 burner ring smooth. The rings would last for quit a while before mushrooming out and causing a bad flame. One thing I did have to do was drill a hole in the top on the ring to relieve any pressure build up due to a sealed top piece on the ring.
If there is a problem you will notice the flame moving around. If there is a problem it is very noticeable.

I've checked the flame several times since I put mine back in service. Pretty blue flame, no signs of soot, or the flame dancing around. I'll keep your reply in mind. If I ever have a problem with the flame I'll remove the chamber and drill a small hole in the top of the dome. I figure the dome shouldn't mushroom out unless the welds break.

[hawkins111]

The other thing you can do to extend the time between overhaul is to cut off the last bend of the flame sensor. That's the last bend that makes the sensor go straight down. That little bit removed from the sensor will not affect it's operation. It will however get the sensor away from the edge of the burner ring. This is not a guess here, this has been done by just about everybody that has serviced a Monitor here in western Alaska for almost 20 years. If you look at Toyo flame sensors you can see that the rod does not have to be right between the wall of the burner and the ring, it can be above the ring a little and still be in the flame. Tom

[wjcroft]

Tom, thanks. So what the cutting of the flame sensor rod does, is to make it less confused by a warped burner ring? It still detects flame even if the ring top has mushroomed significantly? Perhaps Monitor designed the sensor to detect deformed burner rings, because they are operating at less efficiency than unwarped rings? Still if any maintenance operation can be done that prolongs refurbish intervals, that pays for itself in labor hours.

William Croft
Mount Shasta

[FordMan59]

As mentioned in this thread my flame ring in my 422 was welded around the circumference after 6 years of use. In January it will have been an additional 4 years since it was welded and still seems to be in good condition. Unless problems arise that cause the heater to lockout I won't be removing the flame ring for inspection. The current burn mat made with McMaster-Carr material 9323K21 will also be 4 years in service next month.

[FordMan59]

NEW POST 4/24/2025

Been several years since I had the 422 apart and have forgotten the steps to removing the burn chamber. Can someone please give a step by step? Ever since my wife passed away I'm having lots of depression/anxiety issues and memory is just about shot. Any help is greatly appreciated. I thought pictures might also help. I thought I knew how to disassemble it but once I started I quickly realized I have totally forgot what has to be removed and in what order to access and remove the burn chamber. I took the top off ended up putting it back on because nothing looked familiar and didn't want to get it disassembled and not remember how it went back together.

[hawkins111]

Fordman59, I sent you a Private Message.