Flattening V-band Flanges

[SEStone]

My turbo outlet flange will not seal up, and I'm starting to run out of reasons why that might be aside from the flange is warped.

I've tried the MLS gaskets. I've tried reclocking the flange and clamp as best I can. I've tried greasing the clamp on installation to try and get more bite on the flanges. I've tightened the clamp so far I've broken one of them. It just does not want to seal, hot or cold.

My only theory now is that one of the flanges is warped (I hope the downpipe one, as the turbo one is welded to the exhaust housing). What does it take to flatten one of them out? I'm sort of wary at just throwing it at a belt sander, as I don't want to grind away so much material that the face is no longer perpendicular with the axis it's clamped on. If a file or some other hair-brained idea is better, I'd prefer to try that first.

Sam

[loxxrider]

That is very hard to do without turning it on a lathe OR (something that would be much easier if it is still attached to a housing/downpipe) "decking" it with a mill. I really don't think a belt sander will cut it.

Also consider using some RTV copper. Works great for me.

Are you using Chinese v-band flanges? They cost half as much as a good one made in the USA, but they are half the quality too.

[audifreakjim]

I have had success with graphite gasket material

Like this
http://m.grainger.com/mobile/product/Fl ... sket-4CYL8

Or trim to fit

http://www.graftechaet.com/grafoil/graf ... erial.aspx

[SEStone]

I just got done copper RTVing the wastegate flanges and the turbo->downpipe flange along with reinstalling the gasket on that connection. I let it sit for 25 minutes then fired it up for a couple of seconds, and it sounded like there were still leaks somewhere. Before I tightened up the clamps, I visually inspected the joint and it looked great--flange was visually flush and tight all the way around. I only started and idled the car for a couple of seconds, so blowing out the RTV or heating up the joint didn't happen...header was still basically ambient after I shut it off.

I'm thinking I'm going to have to pull the turbo and see if the turbo->header flange is leaking (there's a stainless steel gasket there, IIRC), and if I find nothing there break down and pull the header off to inspect for cracks. Just sucks as I'll need to go buy a coolant containment system for that if I want to do it in my garage.

I would be totally willing to go through all of that work if I was able to find evidence of a crack somewhere, but so far I've got nothing. I've looked over the whole thing as far as I can see, used a bright light and a mirror beyond that, and snuck photos of nearly everywhere else with my iPhone that the mirror couldn't pick out (which actually worked pretty well, the camera+flash took some pretty clear pictures from very odd angles). I can't see any soot being sprayed in the engine bay, and can't find any signs of soot/water/oil/ash around the header or other flanges.

Humph.

Sam

[PRY4SNO]

I'd avoid a belt sander. Too much material would be removed and it's hard to be consistent.

If you have access to an angle grinder, get yourself a stainless disc and press it down flat on the flange for a second or two. Use a 2ft square to check it at 12 o'clock and 3 o'clock to check for square. That usually does it just fine with pipe, and won't take away much material.

Should that sound too aggressive, a file is what I use when I am doing the finishing touches or don't have any parent metal to spare. Push down firm at one corner, 12 o'clock say, and swipe it down to 3 or 6 depending on how good a bite you can get. Then rotate and finish off the remainder.

Otherwise it looks like a trip to your local machinist is in your future.

Hope this helps!

[Toph]

Is it per chance a Holset?

[EDIGREG]

these are great for removing turbos without losing much coolant

http://www.summitracing.com/search/prod ... -and-plugs

[SEStone]

It's a 30R, T3 flange, modified 5-bolt exhaust housing with a v-band welded on to it and the wastegate port plugged. It goes with a modified eBay tube header and custom downpipe, all built by Hank for his personal car years back.

I've made some kind of improvement. It's much quieter in the engine bay, especially when hot. There is still a ticking at idle (I'm running 6-7deg ATDC at idle, which really accentuates exhaust leaks/noises), but it is not nearly as obvious that it's coming from the turbo/wastegate/manifold area. I'm going to try the same RTV treatment on the downpipe->exhaust flange and see where that gets me.

Sam

[my2000apb]

are the vband flanges just flat or do they have the centering/alignment ring/lip on the inside?

[Justin517]

You said it was welded to the exhaust housing... may have been your issue, could have warped from the heat of welding it?

Also... you are positive it is at the V-band itself? I know welding castings can cause cracking issues if not cooled VERY slowly, one of your welds on the turbo maybe? Not sure if that is the same for welding TO castings...

Just throwing ideas out there... I hope I am completely wrong.

[lorge1989]

What type of flange is it? Brand name? Did you by chance swap clamps from a different manufacturer? Most of the time the thickness of the flange will dictate the shape of the clamp, if the wrong one is used you could have issues.

[SEStone]

After copper RTVing a multi-layer gasket for the turbo outlet, I believe that has sealed up for good...no noises or hot gases can be felt coming from around the clamp anymore. Most of my issues now seem to be coming from my wastegate, which uses two 2-bolt flanges and a very small (1.5" or so) v-band flange I believe Hank may have originally stolen from a blow off valve . I believe the 2-bolt flanges may be warped. I copper RTV'd those, but the RTV may be blowing out...the little bit that squeezed out around the edges of the flange is coming off in some sections. I'm going to try an embossed stainless gasket there, but I may have to live with that.

It quiets down when hot with just a slight hiss/tick (sounds like a stock E46 M3, really), but I'm most worried about exhaust dilution affecting any emissions testing or O2 sensor readings.

Sam