8/28/19: Muffler Update
Ok, so I've learned a lot about mufflers since I last posted about my melting floormats.
I went to a muffler shop and told them about my leaking muffler and melting floormats. They listened to the muffler with a stethoscope and couldn't hear any leaks but I told them about the smoke test and they were like hrmm, ok. I also told them about the extreme heat entering the cabin and they were like hrmm, ok. The guy had the personality of a moth. So he recommends that I switch to a Dynomax muffler for $220. It's made by the same parent company as the one I have, Walker, but it's a better product allegedly. I was a bit leary of giving the same manufacturer more money after I've already had 2 mufflers from them leak and this one he is recommending is not fully welded either, just rolled seams like the others I've had. I asked him about building a heatshield for the muffler and he wasn't too enthused about that (or life in general) and said not to worry about it because the Dynomax muffler he wants to sell me has a layer of fiberglass around the outside that should solve the heat issue. I was uneasy about the whole experience and went home and did some research.
Here's what I learned:
1. All mufflers leak smoke. I called Walker's tech support and told them about the situation. They informed me that mufflers have drain holes built into them on the inside for condensation relief and that the location of my leaks matched up perfectly with the muffler schematics he was looking at. The holes are internal and not something you can see from the outside as they are hidden behind the rolled seam. Secondly, he told me that the Dynomax muffler the shop recommended wouldn't help with the heat issues. Even though it does have a layer of fiberglass mat it is thin and mostly to absorb noise and he said that muffler runs just as hot as the one I have now but will be a bit louder.
2. Muffler shops don't know anything about mufflers. This is a common theme that I experience pretty much every week of my life - Professionals are actually consummate amateurs who make a living off people who know even less than they do about the subjet based on the assumption that the professional is actually a professional.
So this guy who owns a muffler shop, works with mufflers every day, knows less about their construction than me, a guy who made one phone call. He didn't know about the drains holes or the fact that both mufflers would run just as hot. Either that or he just wanted to make a sale, customer needs be damned. But wait, there's more. This isn't an isolated incident.
I called Scottsdale Muffler, who originally installed the muffler a few months back, and told them about the issues and they were just like "ya, that happens a lot with mufflers that aren't fully welded, it's just bad manufacturing." and I was gonna get a refund from them. So again, a muffler guy who doesn't know they have drain holes...and also who didn't know that putting a metal box, that gets up to 500 degrees, 5" from the floor would cause heat issues in the cabin even though I specifically asked him that before approving the project.
Ok, so now I was able to come up with a new plan - There's nothing wrong with the muffler, the melting floormat is a result of having it too close to the body. I need a heat shield.
I went to the junkyard and looked under about 20 vehicles. First I pulled a heat shield off of an old Trooper because the muffler was already gone so it was easy to get to. But it was small and would only cover the center section of my muffler so I kept looking. I culled that shield when I pulled the shield off of a Discovery 2 that was bigger and a step in the right direction. Then I found the perfect shield - a 2005 GMC Envoy has the biggest exhaust shield system I've ever seen. It's like 5 feet long and instead of being a regular sheet of metal it is like this extruded sheet metal sandwich with a layer of fiberglass in between. It was a huge pain to remove because the muffler was still in the truck so getting to the bolts holding on the shield was a real challenge. If you go this route, be sure to bring a battery powered reciprocating saw with you to the junk yard and that will make quick work of getting the muffler out of the way.
Back home, I took this giant shield and held it up by the muffler and eye balled it. It looked like it would work so I cut off a piece because it was too long to fit. Then I tried it again, still to long. Cut out off another bit, tried again x repeat. You have to manipulate the shield, bend it, straighten it, etc to get it to roll around the muffler and then up into place but eventually I got it to the maximum size it could be and still fit without having to remove the muffler.
Here you can see the evolution of cuts to get it down to the final size:
Then I sealed off the exposed fiberglass on the cut end by taking a scrap piece of the shield and folding it over the edge and pinching it in place and also adding some jb weld. In retrospect, this was stupidly complicated on my part, I should have just folded the last 1" over itself and it would have been done.
Now the fun part - figuring out how to attach it to the underside of the body. Turns out there are a bunch of extra bolts, threaded into the undercarriage that don't hold anything. It's like those extra buttons that are attached to the bottom of dress shirts, they're there in case you need them. haha, I dunno, probably there are some other components that bolt on there in other markets and not in the USA.
I was able to use 2 of these pre-threaded bolt locations to attached the shield and best part is one of them even matched up with an existing hole in the shield. That left 3 other existing holes in the shield. One of them I found could be used to attached the back end of the shield to the car If I ran a metal strap down from a bolt being used to hold up some part of the rear axle. That left 2 unused pre-existing holes in the shield and I didn't want them to be an easy place for heat to escape like a concentrated jet stream so I jb welded some aluminum blanks to them to seal them up.
Final product:
Rear mount - I used an extra nut to trap a metal strap in between the existing nut on this giant rear suspension bolt. Allowing me to use the strap as a hanger for the shield:
Passenger side mount - used preexisting bolt hole location in body by drilling a new hole in the shield.
Front Mount - Overlapped the new shield and the existing catalytic converter shield and bolted them together. You can also see the pre-existing bolt location I used for the Driver side mount location in this pic.
Driver side mount - used existing unused bolt location in body and existing hole in shield. As you can see, I'm using lock washers and fender washers on all of these bolts because I don't want anything coming loose or rattling.
All done
Overall, I was pleasantly surprised by how this turned out given my rudimentary fab skills and I believe it's probably better than what the muffler shop would have done. They probably would have just driven some sheet metal screws randomly into the floor to hold up a piece of sheet metal. Yes, I know you can buy muffler heat wrap and shields that strap on the muffler but those are like $40-60 whereas this was $15 and I wanted a more OEM like set up with an air gap, then shield to reflect the heat away rather than a wrap that just insulates and traps all that heat in the muffler.
Tested it out yesterday and am super happy - instead of 130 degrees on the floormat, it is now reading at only 88 after a long drive
Also, went wheeling and the clunk in the front suspension is gone so I've confirmed it was the front sway bar.
4 problems a week ago and now 3 are solved. Only the biggest one remains.
Steering Wheel Vibrations - Open - All local diag options exhausted, gonna have Toasty and Ernest check it out to see if it can stump two Montero experts.
Humming Noise from pass front wheel - Solved - freewheel clutch solenoid replaced
Melting floormats / leaky exhaust - Solved - Added muffler heat shield and leaks turned out to be normal from drain holes.
Clunk in front suspension offroad - Solved - Deleted front sway bar (needs new bushings and endlinks)