M923A2 Muffler repair/replace?

[Alexsha]

The muffler on my M923A2 has a bunch of pinholes on the bottom I don't think any are bigger than 1/16". I'm guessing water sitting in the muffler rusted through. It seems solid, but who knows what the condition is like inside. Does the air escaping have much of an effect on the performance of the truck? It doesn't change the noise level as far as I can tell.

If repair, should I weld the holes closed or use a muffler epoxy?

If replace, I think $300ish is very overpriced for the military part. Is there an aftermarker match for the muffler?

 

[M35A2-AZ]

I would try to weld it up first. Then if needed try to find someone that is parting out a truck.

 

[Scar59]

I would weld them up and not worry about it until it really splits opens.

 

[juanprado]

If the bottom has holes it will most likely blow out the bottom as it is rotted. My muffler blew out on my recovery of 250 miles. Water is the culprit and sitting up for long time.

Also, another member had posted a few years ago of a hole in the bottom that directed the hot air to the nylon tubing for the drains causing one tube to melt and a brake pressure loss while driving.

CSMDavis is parting out some trucks. Might be best to get a good used one.

I have a rain flap on it now so it does not collect water.

 

[Suprman]

I would upgrade to a straight pipe

 

[Alexsha]

I would upgrade to a straight pipe

What's the benefit of a straight pipe?

 

[Suprman]

Cheap and less back pressure. Turbo should spool a bit faster. Not really much louder.
Will

 

[Alexsha]

Cheap and less back pressure. Turbo should spool a bit faster. Not really much louder.
Will

Hmm. That might be an option then. Is this a custom part or are there pre-fabbed ones out there?

 

[PWM]

I had a similar problem when I bought my M923A2. The bottom of the muffler was full of holes and the top seam was starting to rust through. When I poked a screwdriver into one of the bottom holes it opened up to be about three inches long and an inch wide. I looked for a replacement but I couldn't find one I could afford. I'm cheap and I have tools so I figured I would fix it myself. I cut both top and bottom seam so I could get at the insides. Once I had it apart I completely gutted the inside of the muffler body. I patched up all the holes with the welder and welded the three pieces back together . Now the truck looks stock, the turbo spools quicker and it sounds good. Even with this modification I can still hear the stereo while I,m driving.

 

[RedOctober]

I am probably straight piping mine soon. My muffler is perfect I could sell it to you if you still interested when I'm done.

 

[Karl kostman]

I found a NOS one for my M925A1 for 300.00 I think I got it through Memphis Equipment. My truck did exactly the same thing as yours and 300.00 bucks out was easier than wrestling with the problem till I ended up replacing it anyway!
KK

 

[Alexsha]

I am probably straight piping mine soon. My muffler is perfect I could sell it to you if you still interested when I'm done.

How much? I fear shipping to UT would be expensive.

I think I'm going to ask around at some local muffler shops if they'll bend me a piece of 4" pipe to replace the muffler and keep the stock stack.

 

[Carlo]

I tried welding the pin holes only to find a short time latter new pin holes appeared in other parts. I then cut out the complete bottom of the muffler. I short time later the top started rusting out! I spent more time fixing it than it was worth. After this I went the straight pipe route. On A2's it's not much louder than stock plus the bennifits of added low torque.

 

[98G]

The turbo does most of the noise reduction on turbo diesels anyway.

Straight pipes should add a bit of throttle response, faster spooling, and maybe a touch more mpg, though I doubt there's all that much restriction in it anyway.

 

[dilligaf13]

A M939 muffler leaking at the bottom is a serious safety issue. My muffler leaked at the bottom, like most that rust out from rain water collecting in the muffler do. This allowed hot exhaust gas to escape downward directly onto the bank of airlines for the air tank bleeders. This resulted in melted air lines and consequently no brakes. No fun and no joke when you're driving down the road, as I was. A roadside removal of the muffler and replacement of the lines corrected the issue but a very uneasy feeling when you're driving and you hear a loud hissing noise followed by the low air light kicking on.

 

[98G]

A M939 muffler leaking at the bottom is a serious safety issue. My muffler leaked at the bottom, like most that rust out from rain water collecting in the muffler do. This allowed hot exhaust gas to escape downward directly onto the bank of airlines for the air tank bleeders. This resulted in melted air lines and consequently no brakes. No fun and no joke when you're driving down the road, as I was. A roadside removal of the muffler and replacement of the lines corrected the issue but a very uneasy feeling when you're driving and you hear a loud hissing noise followed by the low air light kicking on.

Did your spring brakes engage?

 

[jcappeljr]

I have some good used ones for sale,$100 each.

 

[wheelspinner]

I have one here I took out to straight pipe. I believe it was ok but I can check later. Pay the shipping and it's yours.

 

[hgun]

does anybody know the part number for a muffler on the m923a2? mine is rotting. or is there a company making after market ones? I'm undecided on the straight pipe option as of now thanks for your time

 

[Alexsha]

p/n 11669108
nsn 2990010853786