Anyone else having problems with their heat shields?

[Geeshik]

My wife informed me she was getting a really loud rattle when idling, and a scraping sound on occasion when driving up concrete aprons off of the street. I looked under the car and the gas tank heat shield was folded down and bent over. Her Mazda5 is a 2007. The little nuts that hold the heat shield in place pulled clean through it because the heat shield rotted out around them. The studs that the nuts go onto were rusted badly. I soaked them in penetrating oil and I was able to get all but one off without breaking them, but I was very irritated to find that the studs that attatch to the gas tank straps do so on a little sheet metal ear that hangs down. When you try to loosen the nut, the whole ear bends. I ended up using a vise-grip to hold the ear and a 3/8 drive ratchet with a 10mm deepwell socket to get the nuts off. My preference of course, would be a 1/4 inch drive. I had to loosen it a little, soak it again with penetrating oil, tighten it, loosen it, etc. to get each one off without breaking them.



Eventually, the hardware store opened, and i was able to buy the new M6x1.0 pitch nuts and some stainless fender washers to hold what was left of the heat shield up. I put a bunch of antiseize on them and two nuts per stud (the one on the washer was a flange nut and the one on the end, i used a nylock to keep the water and salt from getting on the threads). I could have just cut them shorter, but I didn't want to break out my air tools and fire up my compressor that early in the morning.


Another thing I noted was that in front, right above what looks like the catalytic converter setup, there is a heat shield in the tunnel for the exhaust that is essentially aluminum foil wrapped over some fiberglass insulation. Half of the foil is gone and the insulation is exposed. Is this thing in danger of catching fire? Do I need to order a new shield for it and pull everything apart (exhaust, crossmembers, etc.) just so that I can know my wife and kids are going to be safe? Can I even get a new shield? I would think there should be a recall for an issue like this BEFORE something bad does happen.



This car has 96,000 miles on it. My Focus had 200,000 on it before i had to mess with the heat shields at all.

 

[foxhound1979]

thanks for the pics,

i really have to do the same thing on mine..it's been scraping since last winter and it's making a very annoying sound !

for the front part exposed, i'd check with a garage to see if any kind of danger is possible, don't want to catch a fire or something more dramatic

 

[thaxman]

Another thing I noted was that in front, right above what looks like the catalytic converter setup, there is a heat shield in the tunnel for the exhaust that is essentially aluminum foil wrapped over some fiberglass insulation. Half of the foil is gone and the insulation is exposed. Is this thing in danger of catching fire? Do I need to order a new shield for it and pull everything apart (exhaust, crossmembers, etc.) just so that I can know my wife and kids are going to be safe? Can I even get a new shield? I would think there should be a recall for an issue like this BEFORE something bad does happen.

Before:

After:

Header wrap. We don't get too much rain here, so its held up really well over the last 4-5 mos. If I drive like a madman, I can smell it a bit when I park. My wife has never smelled anything tho.

BTW, the OEM stuff is flammable. I used a BBQ lighter and was able to get it to smolder some, so imagine what 600+F could do. A few years ago there was a run on Mazda5-on-fire videos. Wouldn't be surprised at all if they started here.

 

[Blue Swede]

I have the same problem with my heat shield. It rattles a lot on idle.

 

[sac02]

... BTW, the OEM stuff is flammable. I used a BBQ lighter and was able to get it to smolder some, so imagine what 600+F could do. ...

Holding an open flame to it and having it smolder doesn't really prove it's flammability, or its (lack of) capability as a heat shield. Did it self extinguish when you removed the flame?

Fiberglass insulation is an industry standard (in more than just the auto industry). Fiberglass is non-flammable, though chemicals used on the fiberglass may not be. But in such a heat-shield application, it's a pretty sure bet that the fiberglass wasn't sprayed with something flammable.

Depending on the fuel and what part of the flame you're talking about, the flame of a lighter is anywhere from 1000 to 2000 deg C. (3600 F). WAY WAY WAAAAYYYY hotter than your exhaust.

I'm not saying anything about the durability of the heat shield (obviously it is falling apart, looks like a cheap POS, and needs replacing) but it's not a likely source of fire hazard.



When I took delivery of my 5, I had a rattling heat shield too. The culprit was one of the "crinkle" steel shields rattling against another steel shield. I put at binder clip on it as (what I thought was) a temporary countermeasure, but I may not have to do anything else - I haven't heard it again so far in 9800 miles!

 

[Geeshik]

I'll definitely look into this further then. I don't want to chance anything. Looking at it again last night while I was underneath doing an oil change, it is much worse. The foil has fallen down off of the fiberglass altogether, and is what is left of it is balled up on top of the exhaust now. I read somewhere about a recall for the Mazda5 for vehicles driven in the manual mode of the autostick. Supposedly they installed some sort of heat shield, i am unclear as to where, and there was also a re-tune to prevent ridiculous rpms in manual mode. I checked and the there are no outstanding recalls at this time. Incidentally, we never drive our 5 in manual mode. I suspect the heat shield deterioration has more to do with the heating and cooling cycles and, of course, the shoddy materials utilized. I wonder why they used fiberglass at all. Did you notice a difference in cabin noise levels since you removed yours, thaxman?

Header wrap isn't a terrible idea, but we do get some nasty weather here, and so far this summer, it has been raining almost constantly. I would be hesitant to put it directly under a car, as I have seen what it does to headers over time in engine compartments around here. Even if i have to buy the part and put it in myself, I just want to know my family is safe. I just wish there was a better alternative to the retarded foil on fiberglass.

 

[Geeshik]

I wonder if one could be fashioned from something like this: http://www.heatshieldproducts.com/automotive/heat-shield-and-thermal-barriers/inferno-shield. I am not sure of the dimensions of the factory one, but the stainless seems like a great idea. Cost would be the major prohibiting factor. It looks like the 14x20 piece goes for about $100 on Summit's site, and the larger 24x36 piece goes for a steep $240! If the smaller piece would cover it, I would be willing to pay that much, but wow to the other.

 

[thaxman]

The Autostick recall involved the tailpipe at the rear bumper. Notice your tip probably hangs at least 1" below the plastic. Orig design put it much closer, and morons were driving their cars 6,000+ rpms in 1st around town and the heat travelled all the way down to the tip and melted the bumper.

 

[thaxman]

Oh, and no noticeable noise or heat difference inside. Of course, I already pulled the resonator box out of the intake, so I can hear a tad more noise from that mod. If I drive it a bit harder tho, I can smell the header wrap a bit when I park, even after 6 mos.

 

[Geeshik]

Thanks, thaxman. I sent an email parts request to a Mazda dealer for a heat shield and any information about recalls or service bulletins. I have been unable to find any direct replacements for the heat shield online. Autoanything lists a few of them, but there is no way to tell exactly which one you are looking at on their diagram, as the parts are not numbered to match the diagram. I still think there has to be a better alternative to the fiberglass covered in foil.

As for the others with heat shield rattles, what i did really seemed to work. No more rattles anywhere!

 

[loosenut]

I would consider this https://www.amazon.com/dp/ (commissions earned) it would stick to and conform to the tunnel. You only have to worry about radiant temps as it doesn't come in direct contact with the exhaust. The hottest part of the exhaust will be the converters, as they produce and require high heat (600 -1400 deg) to work properly. My shields are separating as well. For now I have stapled it back together. If that doesn't hold up, I may replace it with the product I linked.

 

[Geeshik]

Went to the local dealer today. The part numbers they gave me were C23556442A and C235-56-442B. It says the two parts interchange. But the price is a whopping $138.72 and they do not stock them.

 

[Wishmaster]

Before:

After:

Header wrap. We don't get too much rain here, so its held up really well over the last 4-5 mos. If I drive like a madman, I can smell it a bit when I park. My wife has never smelled anything tho.

BTW, the OEM stuff is flammable. I used a BBQ lighter and was able to get it to smolder some, so imagine what 600+F could do. A few years ago there was a run on Mazda5-on-fire videos. Wouldn't be surprised at all if they started here.

Mine is doing something similar... can I ask why you only wrapped certain parts? Do the other sections get hot/need to be shielded?

 

[Geeshik]

I am going to make one. I think a 24 guage thickness would be easy enough to form. I ordered a piece of 24 guage 304 stainless that measures 2 feet by 3 feet today from MSC. With shipping it came to $57. Alot cheaper than the dealer cost, and this should last much longer than anything foil-faced. If it isn't enough, I can always add the thermotec adhesive product to it, but I think that would be overkill.

 

[Geeshik]

The stainless sheet came today. It was obvious after looking at it that it would be too short. I started by backing the rear of the car up onto some ramps, setting the parking brake, and then lifting the front high enough to get it just about level with the rear. Then I put 4 jackstands under the front for safety. Next, I removed the 4 bolts on the smaller crossmember (behind the one that goes over the brake lines). One of the ones on the driver's side broke off, so i had to drill and re-tap the hole with an M8x1.25 tap. Next, I removed the plastic push-rivets, and of course, one of them broke as well.

All of the foil was hanging crumpled up on the top of the exhaust so removed it and balled it up so I could get to the fiberglass. Next, I made a cut through the fiberglass with a shears just above the exhaust by the back of the *second cat* and pulled that section out. Then I worked the rest back down the tunnel toward the rear of the car and removed it. I tried to do my best to preserve the overall form of the fiberglass so i would have a pattern to work with. I carefully laid the pieces together on top of the stainless and found that not only was it not going to be long enough, it would not be wide enough either. One side I ended up having to rivet an ear of scrap on to get the passenger side heat shield secured.

[/URL][/IMG] I cut the stainless off where the fiberglass pattern started to go up the tunnel toward the firewall, as there was no way that I could make that compund bend easily. Then I rolled the fiberglass mess and traced it's profile carefully to the sheet. Once that was done, I started cutting it out with an aviation snips.

[/URL][/IMG] It was not quite as easy to work with as I thought it would be, but I got that section cut and formed and put in place. The most difficult part was where the brake lines sit near that forward crossmember.

[/URL][/IMG] I had to cut and bend some extra spots to get it so that the harder material isn't rubbing on the lines. The old insulation probably rubbed on it all day and it was fine. I toyed with the idea of putting what was left of the insulation back on top of the shield I had made, but in the end, I figured I would be better off leaving it out. I snapped a few pictures of the job so far.

It took alot longer than I thought to do though; mostly because I had to try and figure out how to secure the slightly heavier piece to the underbody. The plastic push rivets broke when removing it, so i drilled the hole to 19/64 and installed some 10-24 steel threaded inserts with an insert tool (sorta like a rivet gun).

[/URL][/IMG] My backup plan was to use rubber expanding wellnuts, but I wasn't sure how they would hold up to the heat. I coated the 10-24 x 3/4 stainless screws with antiseize and installed a stainless fender washer and lock washer in hopes that they stay put. For now, the main part by the *second cat* is in place. The *main* cat is just before the flex pipe section. After i looked up in the tunnel once the rat's nest of the old heat shield was out, I was a little perturbed to see that the flex pipe is part of the catalytic converter assmbly on the 5. That is not going to be an inexpensive nor an easy fix when the flex pipe fails. The braiding around it is already completely broke off and spins around the pipe. Maybe I could weld one in, or maybe someone has an aftermarket bolt on section with a flange you can weld on the end of the cat???

Anyway, now I am trying to figure out how to do the rest of the tunnel/firewall.

[/URL][/IMG] I think that is the more important section being that the higher temps occur there. I am pretty beat right now and I am planning a road trip with my wife later this morning, so I think i will clean up and head to bed. I hope the car gets us there and back alright. I will resume my work on this project as soon as i can though.

 

[loosenut]

Geeshik, the leading part of the mid-pipe you are talking about is a cat converter, its just not monitored on federal emission vehicles. (#2 in the below picture) As for the flexpipe, there are replacement flexpipe sections available in the aftermarket that could be welded in, but I wouldn't replace it just because the protective mesh has come free. It may be a long time before the actual flexpipe fails. Good luck with the rest of the install.

1
WU-TWC

(See WARM-UP THREE-WAY CATALYTIC CONVERTER (WU-TWC) INSPECTION [L3].)

2
TWC

 

[Geeshik]

Really? I never would have guessed. I always thought it a resonator as most of the time the intermediate and rear exhaust are usually listed as 'cat-back' exhaust. I guess I learned something today. At least now I don't feel so bad about that 'spensive piece of stainless I put in. Now that I am awake and somewhat alert, I thought about re-wrapping that little piece of tunnel insulation that i removed and installing it temporarily for the trip. I think I might do that just for a little peace of mind.

Haha. I guess not. My wife says we're leaving...

 

[Geeshik]

Tonight, I am happy to report that it got us there and back with our 2 hour drive each way. The interior temps were fine and there were no rattles coming from underneath whatsoever. I also had some time to find my camera cable and get some photos up and correct the bit about the resonator/cat confusion i had. (Thanks, loosenut!)

 

[Geeshik]

Haven't had the wife's car home long enough in conjunction with me being able to work on it so far to finish it. I did "test" a piece of the old heat shield with my map gas torch and it did burn pretty well. It seemed like the fiberglass was ok, but the black cloth/plastic material that lined the top of it really seemed to burn and melt. Maybe the glue that holds it to the fiberglass??? Not a good idea to use that crap though... Anyway, I am on to another project now for a bit; cutting out and welding in some new rocker panels on my Focus. I haven't been able to find a replacement for my 240,000 mile machine for a reasonable price, so i decided to invest a little time and money to make sure it lasts at least a few years more without folding in on itself.

 

[xxechman]

Yeah, I looked under the 2006 Mazda 5 of mine while changing the oil. The fiberglass is a mess. I will attempt to fix the problem the same way you did. Thanks for the post.