Zarathustra[H]

hey all.

I had been hearing really wierd loud vibrating/whirring noises form under my 97 Mercury Sable for a while. From under the hood it sounded as if they were coming from either the catalytic coinverter or the tranny.

I took a look under the car today just to realize that the heat shield for the catalytic converter has a huge dent on it. My current guess is that at certain rpm's the heat shield vibrates causing this noise, casue it was hit and loosened.

The noise is really loud and annoying o I'm trying to find out a way to somehow tighten the heat shield or somethiong, casue I dont want to have to replace the catalytic converter (they are kinda expensive if memory serves me right)

Any tips or hints?

Thanks,
Matt

LunaticSVT

With it being the lower heatshield I would just remove it. Easy enough. If you feel that you really need it on there then just get it spot welded. 2 on each side will do it. if the shield has a large enough dent in it I would look to see if the cat is also damaged. I would put my 2 cents on it being damaged.

If it is then that whirring noise can be the sounds of the gasses passing through the cat and not the shield vibrating.

Zarathustra[H]

Thank you very much for your reply.

Does the fact that thhe whirring seems to stop after the car has warmed up tell you anything? My guess is that the lower heat shield is just touching the cat, and that when it gets warm enough, the connectors expand so it no longer touches. Thats a wild stab in the dark though.

I have meant to reply for some time though, but not had time.

I havnt had time to poke around under the car. Should I expect bolts holding the heat shield on, or is it welded. (Would I have to cut it?)

Is it safe to just remove it? I have heard of people setting patches of grass on fire with old catalytic converter without heat shields. What is your risk asessment?

Thanks for all the help,
Matt

LunaticSVT

I would be blindly answering the warming up issue. Not hearing the noise or seeing the cat and the condition of the shield it is near impossible to give an accurate diagnostics of it.

It is possible that the cat/heatshield is heating up enough so that the expansion of the heated metal is allowing to to be firmly in place. But again that is just a stab in the dark as you put it.

The heat shield should be held in place by 4 or possibly 8 tack welds. I have not seen a heatshield held up by bolts, but nothing escapes that realm of engineering. I would gather up the family farm and bet it is welded just as most are.

I have removed the lower shields from almost every car that I have owned or do own. Only reason being is that I have a tendancy to get them coming off partially causing the vibration noise or tapping.

Is it safe. Yes in most respects it is safe to do so. Now to do it is your choice. I dont park my cars in Grass so I dont worry about heating up the grass enough to catch it on fire. If you park in tall dry grass then your risk is far greater than if you are parking on the concrete.

big1

If you don't have access to a welder and don't want to remove the shield you can use large worm gear clamp's. Like the one's used on hourehold drier vent's.

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