Chasing down an exhaust leak
 

So my car sounds horrible, it has a very raspy exhaust leak that i can not track down.

I have pulled the down pipe off my s366 marmon flange. the mating area was perfectly golden, no sign of black soot.

when i had the motor rebuild my t4 flange and gasket was perfectly golden as well.

NOW i have 2 areas under suspect.

Wastegate flange ( synapse 50mm) and the manifold flange.

The wastegate does have the "fire ring" in there. and when i was up under the car running on a cold start up i could not feel anything from around the wastegate area, nor hear it there, nor did the sound change when i put my hand all over the flange.

I was thinking MAYBE the valve isn't sealing that well. because zeropistons had this wastegate on his car making 600 plus hp. and under HIGH vacuum conditions like an 80 rpm cruise and +20hg of vaccum the leak is silent....

so this leaves my manifold flange... i have no good way of feeling around the flange, what would you recommend? the irons and housings are powder coated dark colors.

when i put it together i put the gaskets on in the right direction. I did reuse the gaskets that came off a JDM pullout. HOWEVER, all the hardware on the twins and the turbos themselves looked extremely new, just a few tiny tiny tiny cracks.


my manifold is from Trackforged, so i guess it could be warped. But i want to know FOR SURE that its the manifold before i pull everything down.

any quick and painless ideas?

2 Ways I like to check for exhaust leaks.

1. get a cheap Halloween style fog machine and let it fill up the exhaust. You will see the fog escape any exhaust leak you will have.

2. get a rubber PVC cap from Home Depot and put An air compressor fitting into it. Then fill it with pressurized air from your compressor. Spray all flanged areas and weld seams with soapy water and look for bubbles.

check you turbo flange bolts/nuts are also tight and torqued. Heat cycling will tend to make them come loose

Everything has been retorqued after about 200 miles since assembly.

Soapy water is the easy button. I'll give it a shot. Hopefully I can clean it off before it gets hot and messes up my coating

Suck some atf into the motor and see where the smoke comes out of.

That won't always work. Exhaust leaks can act as vacuum leaks at low load because they are perpendicular to flow. High rpm and pressure, that can change.

Don't use the soapy water with the car running if you are worried about the coating.

Do it like I said with the exhaust outlet capped with a pressure fitting for a compressor sealed in it. fill it with air and spray everywhere. The cap and fitting will cost under $5 and get you the answer you need.

I lower my compressor to 5psi when I do this and leave it plugged into the cap.

Get a piece of 3/8" fuel line a few few feet long.

Start the car and put the hose to your ear as a makeshift stethoscope.

Move the other end around your manifold, wastegate flange, or other suspect areas.

You will be able to hear the exhaust leak when you get near to it with the hose end and won't burn the shit out of yourself.