Tricks to get exhaust flanges to not leak?

[JZK25]

2 bolt is fine for 3" flanges. Flatten the surfaces, pull them together evenly and use good gaskets.
I find that flanges distort a lot less when hit with decent amps with the MIG rather than fluffing around. Hit the plate with 90% of the heat and do the whole weld at once and they dont buckle as bad.

If they are pre turbo flanges then they need steel sheet gaskets and machined flat flanges.

[mx_paul]

Have seen 3 bolt triangle shaped flanges.. not 4 bolt before?

Your right . If I was to make one I would`t think twice about making it 4 bolt , in saying that I`d get a 3 bolt flange gasket and make the plates to suit . Because I`m a tight cunt and would rather make my own plates then buy them.

[oldcorollas]

does the uptream pipe sit in the downstream flange?
a bit of overlap goes a long way to help stop leakage...

that and Maniseal muffler putty :D


edit: simple liek this.. coat with manisel, slip gasket on, coat with manisel on other side, slip together and bolt and the gas has a longer path to travel to leak

[jmac]

If it's leaking from furtherest points away from the bolts, maybe the clamping of the bolts and numerous thermal cycling have pulled them slightly warped. Rather than filing them flat, get a sand flap wheel, or a grinder if you are steady enough, and DON'T file flat, instead make them curved, just taking metal away from the areas CLOSEST to the bolts. I would put money on that working. It might take a couple of goes, work gradually, not too much taken off, then re-try, and if it still leaked, go a bit further. Done right it'll pinch the formerly leaking sections harder and even if it warps a little further, it'll actually be warping back to 'flat' rather than a warped final shape (if that makes any sense)

Probably upwards of a decade ago, there was a guy (I think he posted here, or maybe on the fullboost forums way back when) who did a diy ghetto 120Y datsun blowthrough. He had head gasket sealing issues, and seriously took to the head (I forget what with - possibly large sanding wheel on 9 inch grinder???) and shaped the deck to a subtle (done freehand) convex shape and it stopped blowng the gasket between the bores in question! Whilst I'd likely stop short of doing it to a head surface, if it worked for that, it'd work fine on an exhaust (comparing combustion pressures to much lower exhaust backpressure.)

I've also had good success over teh years _not_ using maniseal or other gasket goo (though to be fair it has worked for me when I've tried it too) - the trick I use instead is to smear a coat of grease (htb will do) over the gasket on both sides, then bolt up. It seems the grease lets it bite down on the gasket easier, then after the first long drive, it sort of 'burns in' (there will be some smoke coming off the outside of the exhaust at those points whilst it burns for the first say 5 minutes or so) and seals good.

What else - I've also used metallic spray paint sprayed on each side of the gasket (silver in colour, though I'd suspect that any metallic would work). Assemble when the paint has just gone touch dry.

[GTS_215KW]

Similarly as jmac, i dont use the exhaust putty stuff. I just coat the gasket with anti seize (same as i use on the studs/bolts) and just bolt them together. have had no issues.

[RB30-POWER]

seems most things have been covered.

with regards to engine vibrations and twisting, make sure the setup doesn't require a flex joint in there somewhere.

many people over look the obvious which is as the engine torques it can move a fair bit and something has to give, not obvious with engine off and stationary, dump the clutch a few times and see what happens, unless you have solid mounts the engine will move a fair wack and twist the exhaust an equivalent amount.

not sure if this is really going to cause a flange leak, but hey, anything is almost possible in the auto industry in my books.

[Shifty]

I've actually got this issue at the moment on my Bluebird, it's the first time I've built my own exhaust. I thought the flanges were mint but on inspection one of them could actually use a cleanup... although it didn't leak before so I'm not sure what's going on there! I haven't welded anywhere near the flange though so it can't have pulled out of shape at all.

I used one of those normal sorta compression-type gaskets (silver ones that look like they have pinholes in them) and a liberal application of sealant as per the instructions. No dice... sounded like a fucking harley, or subaru, or somethign else shit.

Spent nearly an hour winding out the first two studs, had the shits by then... will do the last stud next week and then clean it right up. Hopefully that, with a new gasket, will solve it.

I guess it only takes a really small leak which then as soon as it starts will open right up...?

[Greg Rust]

OP, most likely the gasket material that you were burning out was an Aramid fibre and NBR binder mix only really suitable for oils and fuels to 205 degC.

What you want for this exact issue is a exfoliated graphite gasket with stainless steel foil insert, has excellent thermal recovery and suitable for constant temps over 500degC.

Look up Garlock 3125TC or 3125SS 1.6mm thick and see if they can mail you a small piece for you to cut your own with from the Sydney branch.
http://www.garlock.com.au/ViewProduc...t=169&region=2

[Russell]

Have seen 3 bolt triangle shaped flanges.. not 4 bolt before?

DiFillipo use them on their headers that have a 3" collector. Had them on mine and had no leak issues.

4 Bolt flanges is what I'd go for.