Ever since I had my Y-Pipe replaced, I've been having issues with exhaust fumes entering the cabin. It only happens when the HVAC is on and set to the 'fresh air' mode. And I can only smell them at idle or very low speeds, like when crawling in traffic.

The replacement Y-Pipe did not seat properly at the firewall connection, so I thought fixing that flange would eliminate the smell. I had a shop cut and reweld the flange, to make a tight seal, but the smell is still there. I had a different shop inspect the exhaust system for leaks and they couldn't find anything wrong. I even went for a ride with the technician, and I couldn't reproduce the problem at that time, so they thought I was crazy...

I've been thinking, since the air intake is in the cowl, what if the leak is actually happening in the EGR system? I tried listening for hissing in that area, but I can't see/hear anything.

Is there a way to visualize the exhaust leak? Is there a method that will make it super easy to find? Something like UV dye for oil leaks, or a smoke machine for EVAP leaks?

 

With the engine in idle, you can have an assistant, using a glove, block the exhaust with his hand while you run around the car, crawl underneth, look under the hood, etc, listening for leaks.

If the engine is about to stall, than have him remove the blockage momentarily and repeat. You'll have to try it both when the engine is cold as well as hot, as some leaks may only show up under certain condition.

Using this method, any leak will become evident.


Phil

 

I'll try that, thank you.

 

If you can't find any exhaust leaks with the method that I outlined in my response, than chances are that what you're smelling is engine oil dripping on the exhaust, and not an exhaust leak. So check for oil leaks, especially from the rear valve cover gaket.

Also check around the PCV valve, for blockages, or leaks. Check the PCV valve hoses, and look for general oil fumes in the engine bay area.

 

Also try seafoam (in the intake manifold). You will see where the exhaust leaks by tracing the white smoke.

 

Come to think of it, I have an oil leak coming from the bottom oil pan. So you may be onto something.

 

Make sure that the oil is indeed leaking from the oil pan and not from somewhere further above, such as the valve cover gaskets, crank seals, etc.

If necessary, a UV oil dye will help you determine the exact source of the leak. It's easier if you clean the engine first.

Phil