Replaced the studs on the manifold to the y pipe, on the front manifold. Tightened up the bots on the rear. Gasketed the flex pipe to y pipe connection. At idle, I can smell exhaust in the van if the HVAC is running. Of course as soon as I start driving, the smell goes away since there's airflow. What am I missing?

 

Sometimes you might be able to isolate the leak if you use a piece of rubber hose and search around with one end held close to your ear and the other listening for the puffing sound. Just be very careful poking around in a running engine especially where the belt and pulleys are.

 

Another way to look for leaks is...If it's cold outside and with a cold engine, start it up. As soon as you see steam coming out of the tail pipe, start looking the system over looking for steam escaping.

 

Definitely been cold enough, no results though. I have a sinking feeling there's a small hole or the leak is in the rear manifold.

 

Aaaahhhhh...That sucks. I went thru that with our 92 Aerostar. Finally started a mis-fire on the right bank. The burnt plug boot showed me the blown manifold gasket location (that was fun...)

 

I have a new to me 06 with 190,000km that has been parked for the last 3 years. It has been on the road for the past 3 weeks and even though it passed the safety, I noticed and pointed it out to the mechanic performing the safety that there was a low throaty sound coming from downstream side of the engine. Louder when cold but still exists once warmed up. One can hear it inside the cab when accelerating. The mechanic did not find any leaks therefore it is either a heat shield or a baffle inside an exhaust component. I think it is coming from bank 1 to the catalytic converter. I went underneath with a wooden broom handle pressing against all exhaust components to see if the pitch changed and I did not notice anything. Ideas?