I've been chasing a whistling sound for years. Is there any chance that the air tube coming from (where the heck does it come from?) Leading to the catalytic converter could be associated with the whistling, as if it was leaking air? Is that thing under any pressure at all? just volume?

How necessary is that tube if I get a new cat that doesn't need it?

 

Smog pump...Probably need it considering you live in Cali

 

I know it's original use is smog related...But would I even need it if a new cat didn't use that air tube? Mehh, scratch that Cali would want me to replace it with exact OEM cats. The Y-pipe setup on this truck is soo crappy though. I want a better one even if it includes all the cats.


But is it possible that my exhaust leak is from this tube?

 

if air moves past anything the right way it can make a whistle, so yes that could be it. also that air tube has no performance gains or whatever, people just cut them and leave them there when they replace/remove there cat.

 

There's a whole section in the Haynes manual that addresses thermactor system noise.

The book could explain it much better than i could.

It's probably a common thing if they took the time to do a writeup on it.

 

All cats require that tube.

 

I didn't bother to fix the air tube when it rusted off the 90 E-150. Just tapped inlet on the cat either 1/2 or 3/8 NPT and installed a BI plug.

The loose tube would rattle around a little but there was never anything more than a soft puff..puff..puff sound.

The thermactor whistle is probably coming from when the system is venting directly to the atmosphere through the bypass valve. It's sometimes located just after the outlet of the smog pump.

 

The pipe provides oxygen to promote combustion of unburnt fuel. If it's not there the cat can clog.

 

I probably got off lucky.

My sentiment these days is that it's better to try and keep all of the systems the truck came with intact & in good working order if possible.

You just never know. A couple of years from now state or federal laws could change and your vehicle would be required to pass a yearly emissions test.

 

I don't worry about what might happen. It's my truck I do what I want to it. Although I did save some parts, just so I still have the complete truck.