First off, you'll have to forgive my ignorance when it comes to exhaust-type things... In the twenty-plus years I've been wrenching on my cars, I've never really touched anything in the "blow" department. Also, be it in my Haynes or in the various manuals on foxed.ca, I've been unable to locate a good diagram of the stock exhaust. I'm going to do my best to describe the parts and take a shot at naming them correctly.

So, one of the things I've been meaning to do for a couple seasons now is swap out my transmission mount; I had been getting the occasional violent jostling when shifting into first. While I'm under the car working those four bolts, no doubt I had occasion to smack the exhaust a couple times. Finally got that done last weekend and the wife and I take a little trip out for lunch. On the drive home, the car starts idling fairly high (~2200-2400 RPM) and quite lumpy. By the time I get home and pop the hood, there's a nice wisp of smoke coming from down below and the thermal reactor (I think) is RED hot. Shut her down, spend the week researching.

This afternoon, I get back out there with conviction and some troubleshooting steps gleaned from this forum (Secondaries stuck? Vacuum leak? Clogged cat?). I remove the air filter housing, start her up, and start poking around. After about five minutes of high, uneven idle, the smoke comes back and everything starts sounding a lot more "exhaust-leaky". I shut the car off and look under the passenger side of the car to see that, joy of all joys, my freaking car is on fire. The heat exchanger (again, I think. Photo below.) along with its silicone hose are in flames. I run inside, grab the extinguisher, and give it a nice dousing. Fortunately, it seems like I've avoided disaster.

So what's the diagnosis? Considering both the red-hot exhaust and the high, lumpy idle issues started simultaneously, I'd imagine they're related. As far as I know, it's the same exhaust that's been on the car for 37 years... Could a clog cause enough heat to create flames and a vacuum leak? This could be the excuse I need to go full RB exhaust.

Thanks in advance. I'm gonna have a beer.

-Jay

 

Sounds like running lean,vacuum leak(s)severe enough,engine can get hot enough to ignite combustibles.

How about some info on your car,year,miles,what recent maintenance?

 

1983 GSL 5MT w/ just under 75k. Recent possibly relevant stuff:
Replace tranny mount (2020)
Replace pos and neg battery cables (2020)
Reseal oil pan (2019)
Replace beehive o-rings (2019)
Oil and coolant change (2019)
Cap, rotor, plugs, wires (2014-ish)

 

You've got Exhaust Cancer Jay.

You need to remove all the stock exhaust stuff and go RB.

RB isn't making good exhausts these day, but it will be better than the fire you got going on down there now.

 

The 83 will not have a thermal reactor or heat exchanger. Only the 79 and 80 model years had this in the U.S. The exhaust part that you have pictured is the catalytic converter. If its glowing then it's likely breaking apart internally and clogged. If the exhaust manifold is glowing then you likely have issues with the engine running lean.

If just the converter is glowing you can check exhaust pressure at the muffler's tips with the engine idling. Should be quite a bit of pressure. If not then the converter is likely bad. Remove and inspect the main converter and the two monolith converters ahead of it. Often times the two monolith converters break apart and throw the material into the main converter causing it to plug and fail. All must be replaced at the same time. Replace with a full Racing Beat exhaust system for best results. Or you can take thebcar to an exhaust shop and have them make you a new pipe from the manifold to the converter and replace the converter. Personally I feel as though the best option is the RB exhaust.

 

Thanks for the help, fellas. I should have mentioned that everything was running perfectly fine --nice and steady 750 RPM idle, no visible flames...-- before I went under the car and started bangin' around. New RB exhaust it is. Now, how do I get the wife to green-light it?

 

To be fair, new exhaust components are not available from Mazda any longer so you really have no choice. And even if they were, the price of a new main converter is twice what RB charges for a complete exhaust. That's the way I would spin it.

 

Tell the wife that your car is going to burn down to the ground unless you get an RB exhaust in there. Reason with her by saying the old stuff is so old it's fire prone. It caught fire once already... right? It's likely to catch fire even more easily the next time. Better get some new fire proof stuff in there like RB. Oh, also tell her that new OEM components are way more expensive than RB, if you can even find NOS OEM of anything these days. Better go RB and save money.

 

This is the only one I've encountered and I'm not entirely sure what the top part is. At least the bottom part says "83" :P

 

most women are really dumb when it comes to cars. I told my girlfriend that it cost $2000 to fix the rear brake light. She bought it! She did price out what a brake caliper would cost, so this chick was pretty smart when she could look up something.

I once replaced the cat converter with a cherry bomb glass pack. It was to spite the N J emissions inspection regs. The car was loud and stinky! Took a whole weekend to do it.

Tell your wife, it's either RB exhaust or a new car. Or a used car that you don't already know how to fix everything on.