I had your exact same problem and been chasing exhaust leaks for a while..

i took it to a machine shop also, but it still ended up still leaking. I then took it over to a buddy who had just bought a belt sander, and put it on for like 10-15 minutes and finally got it flat. bolted it on, and it was much quieter. i would take it back to the shop and tell them it still isnt flat, they may have not fully trued the surface in the interest of time

the other cause is your wastegates are indeed leaking. i recently switched from dual 38mm external wgs to an internal wg setup, and its so quiet now. it could be caused by the spring and valve not seating properly. The flanges are very difficult to resurface, since they have that inner ring area that you cant get to. you may want to just do the inner ring surface on the wg side, and the outer surface on the manifold side and see if it helps

another thing that seems to help is using FD gaskets, which are two-piece. Or just cut out the center section of the FC gasket, which does nothing and can cause leaks

 

I do have suspicion on how true the resurfacing turned out. At first I had forgot the second gasket and I had the bolts snug up to the lock washer using the used OEM gasket only. When I realize I had forgot the second gasket and removed the manifold I noticed where the manifold made and didn't make contact on the copper spray on the used OEM gasket. I told myself it was because I never finished tightening it. It just might need resurfacing.

Switching from external to internal wastage is not an option as I don't have the funds to re do my entire turbo kit. I was also told that all vband waste gates are going to leak a little and turblown comment seems to confirmed it. I remember the car not leaking at all the very first hundred miles or so. I'm hopeful that i can get her back to that with "minimal" work and funds.

 

i wouldn't bother with a copper gasket, the material simply won't hold up under the heat.

REMFLEX makes a thick laminated carbon gasket but i have my doubts that it would hold up either.
http://catalog.remflex.com/MAZDA_Hea...t_p/58-001.htm

 

OK I guess I have a game plan. Get stethoscope and find leak. If its the same header flange I will take back to shop for resurfacing and I'm going to man up and buy factory 100$+ factory Mazda gasket.

 

honestly i doubt it is from the manifold flange if the gaskets were doubled up. the manifold may have a cracked weld or leaking elsewhere. but i could be wrong, it may be severely warped due to cheap flange material.

wear some gloves with the stethescope so you can try to check every angle possible.

 

For sure! That crap gets hot way to fast. Its ridiculous, I can never feel around long enough to find it.

When I had the manifold out I inspected it really good. It did not have a crack. Although the flange was pretty warped. It was visible to the eye while looking at the "flat surface"

 

I know most people are going to be against it, but I would give this stuff a try.
http://www.summitracing.com/parts/de...FYKUfgodRiMACA

Our time attack e46 m3 has a gtx35r making 640 whp had a massive exhaust leak. We resanded the manifold and used this stuff with our stock gaskets and have no leak problems. its not endurance racing, but the car gets pushed really hard for 20 minute sessions

 

if it does work then it would be a good cure for those cracked cast iron manifolds/turbos with one foot in the grave.

 

I ordered an Mazda gasket this morning. I haven't even gotten the stethoscope nor found the leak yet, but Im determined to fix cause I'm desperate for some damn wheel time. Damn the exhaust leak!

About that DEI product, I trust DEI and I'm curious if I could try to use that for the vbands. The manifold flange if leaking will just get resurface ,again, and use he Mazda gasket.

 

I'd be afraid of that stuff squeezing off into the exhaust ports.

Cheap doesn't always equal good.

 

Yeh, youre right, there are to many unknowns to try it.

 

92$ shipped. Just in case.

 

I got a Stethoscope for 2$. Win! But I must be any good at using it because I tried for a bit without success. I would just slide the end if stethoscope around the edge of mating surfaces without picking up any areas that stood out. :/

 

you took off the actual probe and just used the open ended tube right?

 

It just comes with an open ended metal tube and a extension tube.

 

is the tube hollow at the end? meaning can you blow through it to reach the earpieces?

 

Yes it is. I had a hard time finding an area that sounded off, different , or stood out. I am pretty sure that there is a leak pre turbo by the distinct "tsk tsk" sound. I do want to try the stethoscope a couple more time because I had a hard time getting the end of tube to some of the areas.

 

No luck pin pointing the area. My stethoscope is not hollow like I had thought it was. I will try to modify the stethoscope or purchase a new, hollow, one. Hopefully I can get this figured out asap.

 

you should be able to feel the leak pretty easily with your hands. jack up the car, get under there and feel for air around the manifold. do it right after a cold start to minimize burns. check manifold flange and turbo flange.

also, not sure if it has already been checked, but some wastegates come with an insert that the valve sits on, did you forget to install those?

 

Use a torch to locate the leak

 

Wastegate valve seats are definately in.
I tried using my hands to feel for it with no success.


How do you use a torch to find an exhaust leak.

 

never heard of using a torch method, but that reminds me of the smoke tester to test for leaks

 

I think one of my friends has one of those l exhaust fume sniffer thingies. I will try that this weekend.

 

I can't use the exhaust sniffer. It was a friend of a friends.

So I have read of other possible ways of finding an exhaust leak. I'm just want to run them by you guys.

1. Attach a vacuum cleaner to the tail pipe using duct tape.
2. Pressurise through the tail pipe kinda like checking for boost leaks.

I could listen for hissing for both of them and for #2 ,I could also use soap water just like a boost leak test.

Now my only concern is pressurizing the exhaust. It should be OK, right?

 

I found them!! Those sneaky little fckrs.

From trial and error I have found the most effective exhaust leak finding method, period.

Basically, its a boost leak test. HEre is what i did. I used a shop vac. and put the hose on the pusher side not the vacuum side. I then Duct taped the hose to the tail pipe. ALl you need after this is soap&water mix in a spray bottle. Spray all suspect areas down really good with soap.water. Crank the shop vac. on and watch the bubble show. THere wont be any questions whether its leaking or not.

MY found leaks include.

*Downpipe flex pipe is leaking ALOT! THis is the main leak i have.... SUrprised how bad it leaks here.
*Both wastegates vband flanges leak a little.
*Downpipe/turbo V-band leaks a little
*Downpipe/offroad pipe v-band leaks a little.


MAnifold to engine flange = 0 leaks. (will try again shortly to be 100% sure)
MAnifold to turbo = 0 leaks

what have a learned....Damn vbands are a pain in the butt. I couldnt imagine using them for and would never use v-bands for intercooler piping... I used to think it was cool but.... real world shows differently.