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I'm more than a little surprised that searching for "fuel tank" and "heat shield" brings up no questions on mechanics.SE. Indeed the very keyword "heat shield" has not yet been added. (I cannot add it from my side.) In any case...

A car will typically have several heat shields. The ones along the center of a car are there to keep the feet of the occupants cool in the summer, and perhaps to increase the sound insulation.

The heat shield right under the spare tire (or "doughnut") keeps the rubber in that tire from melting, or disintegrating too soon.

The one I'm concerned about is the one under the fuel tank. When I look at how it is sculpted, I feel that keeping the fuel tank cool is only one of its design parameters. It also has channels that seem to lead any leaking fuel away from the exhaust pipe, with the drainage holes quite far from the exhaust pipe.

fuel tank heat shield

The idea then, presumably, is that even a drop of fuel (from a crack, from a tiny hole, from rust, or from stress fracture during a minor collision) will instantly ignite if it touches the exhaust pipe, possibly leading to a catastrophe (such as starting to bake the occupants inside or, worse, the tank exploding). A fire there seems risky because the driver will not even know, unless good samaritans happen to be nearby and honk like crazy.

It is not unusual to hear folks who discarded their rusted fuel tank heat shield say that they have been "driving for years without an incident".

As you see, I am already convinced that it's more than a little unwise to drive without the fuel tank heat shield. Yet it's quite common to hear people advising to drive without one. If you are in that camp, could you argue for that point of view? (You are hereby held harmless from any liability!) Even if you wouldn't do it yourself, feel free to act as a devil's advocate and illustrate how that argument might go.

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  • There was a question similar to this posted earlier, oddly I can’t find it.
    – Solar Mike
    Commented Mar 1, 2021 at 17:03
  • This is more of a rant than a question. There are many components of a motor vehicle with a higher risk factor than a missing heat shield - for example brakes and tires.
    – alephzero
    Commented Mar 2, 2021 at 17:14
  • @alephzero If you're able to elaborate on the point of view you so succinctly express, and which is specifically sought by the question, we're all glad to hear your wisdom (no sarcasm intended). In the meantime, however, do spare us judgmental comments, which anyway go against the spirit of SE.
    – Sam7919
    Commented Mar 2, 2021 at 17:29

2 Answers 2

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Immagine:

  • A protective measure that separates a very hot surface from a liquid tank, often in precarious state.
  • The liquid tank contains, at average, 60 liters of a highly inflammable liquid.
  • The hot surface is a few centimeters under the container.
  • The liquid has an ignition point around the temperature of the hot surface.
  • Attached is at least one human being, in an enclosure, one or two meters apart from the container. The enclosure is lined with flammable plastic.
  • The whole system is travelling at around 130 km/h, around other similar systems.

Nobody sane will tell you that said "protective measure" is unnecessary, at least in written.

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The rationality of this is, if the manufactures spent the money to install it, it most likely serves a very important function. The function may not be obvious to us at first, but many times it surfaces it's head when after 20,000 miles or so we discover scorched wiring or overheated fuel or hot floorboards. If the shield is available, it is always a good idea to have it replaced. Sometimes you have to get a little inginuitive with securing them, but then you know they are protecting whatever.

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