Metallic rattling near exhaust - safety question

I hear a metallic rattling near the exhaust when I accelerate and it goes away when I am cruising. Can be inconsistent though. Much louder when just starting from a stopped position. A guy at a gas station said it’s just heat shields rattling and not to worry. Talked to someone else and they said you need to be sure the gas tank doesn’t get too hot, or it could explode. Is that a valid concern?

 

No.

 

I'd like to meet the person that said your gas tank can explode.

Anyway, if the rattling is inconsistent and changes with acceleration, etc., just check underneath when the truck is cold and tighten up your bolts.

 

Ha. Thanks so much. I figured it was a bogus concern but I wanted to be really really positive. I do wonder if the sound is due to a hot day because I’ve never heard it before

 

My brain is going to explode over how stupid gas station guy is.

 

Get under your truck (with engine off) and tap on different components with your hand or the handle end of a screwdriver to try to simulate the noise. You may be able to isolate the component(s) that are making noise.

 

I'll repost info:
As many have heard rattles underneath their trucks look at the exhaust heat shields as they corrode and the holes gets too big so you have to take the nut off and add larger washers to hold them up. I added 2 washers with upper most 1 with a larger hole to fit over the stud post first so next washer will lock the heat shield tight (when you have the nut off you will see what I mean). The catalytic converter under the drivers side on 4x4 have a 2 piece heat shield and those usually have the 2 bolts rush out and then a thin muffler clamp (2 1/2 inch) holding it on. It protects the front driveshaft and boot. I used a 2 3/4 stainless hose clamp instead of a muffler clamp which looked like overkill as a lightweight shield and the 2 bolts hold it clamped around the cat.

 

Do you know at what rpm it starts to rattle? I have a rattle that comes on around 2900-3000 and goes away at 4000. I checked the heat shields and they're not rattling.

 

I like to hit different parts of the exhaust system with a rubber mallet. You don't need to use much force; just kind of tap around in different areas. You will locate the source of the noise pretty quickly.

My vote is for the heat shields around the muffler and/or catalytic converter.

 

Yes, that’s exactly the RPMs for me as well! Actually now the rattling has gone away and it’s kust a typical loud muffler noise.

 

Of course your gas tank can get hot enough to vent through the charcoal canister.

Although it is not going to happen in everyday driving to the point it looks impressive.

Some day I might sit down and do the math if I get really bored.

 

The gas tank is on the opposite side of the truck from the exhaust and it's nowhere close enough to be able to heat it up

 

Hahahah

 

Did I say from the exhaust ??

Reach a critical temperature it will expend and push out the charcoal canister .

Hence my comment about having to do the math

 

do you drive your truck at 2100 rpm
that is where my rattles are in all gears (most of the time not all the time)

i rarely go over 3k rpm unless in 5th grear, but left in 4th gear once to get high rpms and there was vibration up there to

dam 4k rpm you must be flying! by the time i get engine up that high I am probably hitting 100mph

 

But that's still only if the heat shields fall OFF. If they're there and just rattling, they are still doing their job. Gas tank explodey guy needs to stop giving out car maintenance advice, lol