Hissing Sound

Hi,
New member here.
I have a 2005 Tacoma, 4 cyl with 325,000+ miles. Been running great. Stopped by my mechanic today and he has 40+ vehicles in his lot, so kind of backed up.

In the last couple of weeks, it started behaving a little odd. If I kick it up to 3k-4k RPM, like to get up a steep hill, it makes a noise like it's either sucking or blowing air. No combustion sounds just a really loud hiss. Also, either my imagination or it seems to have less power when this happens.

I've had some issues lately that have kept me from getting too deep into checking it out. I did check the air intake systems and don't see any loose or broken connections there.

I tried to check it out in the driveway but the noise does not happen when the truck is in park and at least 4k RPM.

Any ideas from that description?

Thanks

 

Could be a pin hole leak in the exhaust caused by a small amount of rust, or when loaded exhaust can be escaping past a gasket, they are material and leak over time.

Because its only under load its likely not a huge deal, but doesnt hurt to get it looked at.

 

Sounds like maybe you have a plugged catyletic converter, an exhaust backpressure test would be needed to verify.

 

Good advice above, sounds like an exhaust leak.

Oftentimes the exhaust will find a path around a partially clogged converter, and leak out through a gasket or connection. Also, with that many miles the exhaust could be rusty which makes it easier for a leak to develop

Even without a clogged converter, a small exhaust leak can affect backpressure which can make it feel a little sluggish

Get under the truck and look for black soot. Also a mechanics stethoscope with the metal tip removed (just the hose) can help locate the source of the sound

 

Welcome to TW.

 

An easy way to conduct this test requires the use of a shop vac. You plug the hose into the exhaust port on the shop vac and put the other end into the tailpipe. Turn on the vacuum then go around your exhaust with a squirt bottle with a dish soap and water mixture. Make sure you squirt all the connection points but if you have a pinhole, you might hear it when you turn on the vacuum. Follow the bubbles.

-J

 

Y pipe to manifolds do leak and make it run richer (less MPG too) with less power when mine went