My car was making a rattling noise when driving with very low RPM and slow, or very high RPM and fast. When cruising it was OK. Drove car to the mechanic and he said that cat is broken. He replaced the cat and now everything is OK. Anyway I looked under the car at what he did and checked in my cars manual, and noticed that there should be a heat shield over the cat. I googled and somewhere it said that without heat shield over the cat the body of car can get so hot you can feel the heat in the cabin on the floors and its not OK.

So did he remove the heat shield? Do my car need a cat heat shield? My car is Renault Clio mk.2

I also suspect that the rattling noise came from heat shield and he just took it off and overcharge me for new cat.

  • Hi and welcome.
    – mike65535
    Commented Nov 8, 2018 at 17:00

3 Answers 3


Rule of thumb: If the manufacturer put it in, it's needed. Not only can the catalytic converter's heat warm up the interior of the car, it can cause a fire if you park on dry grass or leaves.

As to whether the mechanic removed it - it's not really for us to say - you'd have to know if it was there before you brought it in. But I'd be suspicious.


Rang the mechanic and asked if he removed the heat shield, and he said he did and that the heat shield is not needed, and that this new cat has an integrated heat shield. Yes the new cat does have welded heat shield on, BUT it is pointed down instead of up at the car body. And the welded-on heat shield is pointless IMO. Looks like I will have to be without the heat shield. Just drove 30min and the cat is really really hot. And right next to the cat is a oil canister for engine oil, that is also quite hot, but I don't know if it is hot from the engine oil itself(does engine oil get hot?). Well I hope I don't get blown up lol

  • Pointed down prevents dry leaves/grass catching on fire.
    – mike65535
    Commented Nov 8, 2018 at 18:14
  • And, yes, engine oil gets hot.
    – mike65535
    Commented Nov 8, 2018 at 21:18
  • 1
    Also, the shield just has to have an air gap to work. The air gap doesn't have to be that big to be effective. Commented Nov 8, 2018 at 22:41
  • You may want to send a note to the Community Moderator Team and have them combine your two accounts. Commented Nov 8, 2018 at 22:43

They are necessary. CATS get hotter than Hades especially if they sit directly behind a Turbo. I went from a standard CAT to a 3" Dump pipe & High flow CAT & drove it for a while without a Heat shield because the OEM heat shield would no longer fit the new pipes. I soon made one up though because the heat that the new CAT generated melted my Brake Master cylinder.

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