ok this is the deal...hopefully someone can help. i have a pretty bad exhaust leak from somewhere up where the turbo and the downpipe is. At first I thought it was a blown gasket because I had used the old one from when I put in the downpipe. But the other day i bought a gasket this one seemed to be thicker and i put it in but started up and its leaking still. So i dunno any thoughts about how to find the leak or what it might be? i could only think it being the downpipe flange or a cracked turbo manifold. which hopefully its not. please help...

 

if you did not have a exhaust leak before you changed your downpipe it has to be that the bolts where not tight to spec look at the new gasket and check for a black spot if it has one thats your leak

 

Check the flange for warpage. Buy a big mill file and carefully file the downpipe flange flat. This fixed mine. Or take it to a machine shop and have them grind that face flat. I suspect stainless downpipes warp to relieve the thermal stresses put there by welding, or that it wasn't flat to begin with (again, due to the welding process).

When you re-use the gasket, take a thin knife and wedge it in between the layers. Carefully pry apart the layers of the gasket just a little bit, so it's a little thicker like when it was new. Every time you install the gasket this will get compressed flat. Clean off any corrosion, too.

Dave

 

thanks guys. i think my next step is to try and grind the face flat. This could probibly be the problem because i had bought my dp used. is this a common problem with these downpipes? and just to clear up KINETIK i didnt have the leak when i first put the downpipe on. but it could just be that because when i pulled on one of the bolts the sound changed a little bit but i could not try and tighten the top 2 because the car was on and was already to hot. Also can i spray some oil into the intake so the smoke will come out from the leak?

 

You could very likely have a crack around the flange to DP weld. If there isn't a crack, and your flange is imperfect, you can use this stuff with better results than the the gasket your using:

https://www.rx7club.com/single-turbo-rx-7s-23/v-band-flange-gasket-467421/

I'd grind the flange face flat on a wide belt sander, and still use a compressible gasket.

 

Watch the wide belt sander - it tends to create a round surface instead of a perfectly flat one. I had someone do this for me, and it didn't make for a flat surface. And as luck would have it, it took off the extra material at the top/bottom edges of the pipe flange, where it's most difficult to get a good seal anyway.

Dave

 

My downpipe flange had to be resurfaced to make it flat and it was brand new.

I agree with Dave. The best way to true up the flange is to use a long flat metal file. File it across the surface 12 o'clock to 6 o'clock and then 9 to 3 and then in an x pattern relative to what youve already done. You can black out the face with magic marker to see where low spots are as you file. When you think youre done, check in all directions with a straight edge.

I also carefully separated the layers of the gasket and placed a couple of strands of 0.020" copper wire concentrically between the gasket leaves. After running the car up to temp, I retorqued the bolts.

chuck

 

If it is the gasket, as someone mentioned, you can tell by looking at it after running the car a bit. Your smoke idea is good. Get it to burn oil which will stain the leak and give you somewhere to concentrate. After this, pull the downpipe gasket back off and look to see if any black exhaust smoot made its way from the inner circle and off the gasket. If not, the gasket is doing its job. Sounds to me like a small crack in your manifold for some reason.

Raj

 

What brand DP? I got the Ebay Megan Racing one and the sealing isn't one of its fitment issues.

 

its a pettit racing dp. thanks for all the input. we'll see wat happens

 

Don't mean to argue for the sake of it, but a flat surface can be achieved with a stand alone industrial belt sander (not talking 'bout some cordless hand held ****) . A sander that has a well tensioned belt with a "flat" steel backplate, combined with the right touch is faster and better than using a hand file. Sorry whoever did your job drank a 40 at lunch and then used poorly maintained equipment to do the job! C'mon, seriously.

 

There is a reason that they dont use a belt sander in a machine shop for creating a planar surface. Regardless of tension, the belt will have a tendency to change shape as it passes over the surface being planed. If one could feed the flange surface perpendicular to the belt in fixed increments and the belt sander was fixed in position, then you would probably get a usable surface. Doing it by hand would yield questionable results especially on such a small surface area.

chuck

 

I've often used a belt sander to achieve a flat surface on exhaust flanges. However, it takes a VERY deft touch to get the surface really flat. The biggest problem is to not let the other end of the pipe move around or change positions while sanding. That will certainly result in a convex sanded surface.

As I said, it can be done, but it's a bit difficult to do a good job.

 

What does a leak from that area sound like? Or did you use the cigarette smoke method to find it?

 

wat is the cigarette smoke methond?

 

In the garage, with the engine idling and fans off, pass a lit cig around the flange and watch the rising smoke to see if it is disrupted by gasses squirting out of the exhaust.

You can also use a burning stick of incense or punk, depending on your political persuasion.

 

I just pretension the bolts of the flange about halfway, and use a .002" feeler gauge to probe for gaps.

Dave

 

My new car spontaiously got an exhaust leak in the same area sunday night... im thinking its not the DP unfortunatly... But was wondering if anyone could direct me to a blow up diagram of the turbo/manifold area (ive had the car less than a week, so no time to get a shop manual yet)

 

www.iluvmyrx7.com or use the first sticky thread.

Now you have a shop manual