i have a slight exhaust leak where my y-pipe connects to my headers. i didn't know it for quite a while but when i took it to my mechanic it was obviously noticible enough for him to hear it when it put his head near the bottom of the car. so i've been riding around with a nice little leak for a while. is this something that will damage anything or decrease performance? i can smell a "sulfury" smell when i'm at WOT in the cabin of the car so i know it's gotta be sort of a decent leak. i just wanna know how urgent this is to get fixed. decrease in performance?

 

yup exhaust leak decreases performance and gas mileage because it can create backpressure and turbulence in the exhaust and it sucks. i think most 4th gen are know to have exhaust leak around the flexpipe area. i had a bad one a while ago but i just replaced the whole y-pipe with the budget y-pipe special and it feels great!

 

Of course it will decrease power...you're losing air. It's not a massive amount but it's still a lose. Get it fixed.

 

what u might be experiencing is the beez in the can sound.. they y pipe might have a loud flex section.. the smell could be something else...

 

It's not true that a leak will reduce power or increase backpressure or whatever. It will emit extremely high temperature gas at the point of the leak and smell bad because the exhaust in the y-pipe hasn't yet been reduced by either catalytic converter.

Definitely get the leak fixed. It might be as simple as a loose bolt or needing a new gasket.

Dave

 

Should still lose some power...I lost power when I had my leak. Plus the ridiculously loud noise...that sucked

 

awesome. i will definetly get it checked out. thanks for the advice!

 

Actually, if his leak is at the exhaust flange, he will lose power and gas mileage, though indirectly. If more air is passing by the oxygen sensors, they read as lean and the PCM adds fuel to attempt to go stoich, running overly rich.

 

I have a small crack in the Flex pipe(Y pipe) where it connects with the pipe that goes to catalytic converter. I don't hear any noise but my gas mileage is horrible (13mpg / 200miles per tank -city). I replaced everything that affects gas mileage.

The crack is small , so will it significantly improve my gas mileage if I replace it ? Should I replace it ?
How much the cheapest Y pipe costs ?

 

I believe the oxygen sensors are not read when the car is under heavy throttle.

Plus it would take a pretty big leak.

 

Yes, at WOT in open loop the O2 sensors are ignored, as well I believe the IAT and some other information, but it would hurt his 'normal driving' performance (which for me and many others is open loop, but I digress...). Not necessarily physically big, but it would take a somewhat large volume of air flow to make a large performance difference.

 

When i had an exhaust leak in my old max partial throttle power was down and my MPG was atrocious. Leak was at the exhaust manifold/y-pipe junction.

 

I just got done replacing my exhaust flange gaskets not 15 minutes ago (fun in the cold weather here), and I still have a damn leak. Those two were new, as is a cat gasket I put in a few weeks ago, the other one is in good shape (from several months ago)...I'm guessing only thing left is the flex section, as I doubt I blew out the gasket on the manifold.

Oh well, excuse for a y-pipe.

 

Depending on how many times they were loosened/retightened the nuts and/or studs may need replacing. I had a leak at the same spot and it didn't go away until i replaced both of them.

 

Hmm...do you mean they just may have stretched/deformed such that they won't hold the y-pipe flange onto the exhaust manifold tightly/uniformly?

That would suck. I've removed the y-pipe maybe 5 times, I doubt before me it had ever been off before.

 

Yea. The FSM actually recommends replacing the nuts every time they're removed but you can get away without reusing them a few times. But 5 times is getting up there. It's worth a try since they're relative inexpensive.

 

Just the nuts, or studs as well? I've got a whole box of 12x1.25 'exhaust' nuts in my box at school (bought them specifically because I've worked on several Nissans with screwed up exhaust nuts, easy to replace them if I've got a bunch sitting there). Replacing all 6 nuts (actually 5, I've replaced one already because I...somehow lost it while laying underneath the car the entire time) is no real problem, guess it's worth a shot, anyway.

 

I would try replacing just the nuts for now. Of course, if you replaced the studs as well you could absolutely eliminate the fasteners as the cause of the leak.