Flange leak - midpipe to silencer

[alex87f]

Hello guys,

I recently swapped my silencer for an aftermarket unit (that has been an absolute can of worms, but it's another matter), and am now getting a leak at the midpipe to silencer flange.

I first tightened the flange as hard as I was willing to go, but there was still a noticeable gap between the outer edge of both flanges (which you can sorta see in the pic below, though it was a lot worse on the other side), and sure enough there was an exhaust leak at that point.
It's worth noting the stock midpipe flange is in pretty rough shape, I had to take the car to a shop which spent half an hour convincing it to separate itself from the stock silencer flange. Rust was involved.



Then, I swapped the gasket for a new one, and while that was no luxury, things didn't improve at all. Still leaking.

Resorted to using JB weld hi-temp paste, which looked terrible but plugged the leak pretty well, for about a day...



... and then it cracked.



What's my next move? I was thinking of using a high temp sealant, or just getting a new midpipe (because I like throwing money at problems , but also because the shop I bought the silencer from is giving me a nice discount for my other troubles).

What do you reckon?

Best regards,
Alex

[Yoshoobaroo]

One of the flanges is bent.
Take both parts off, measure which one is bent and have it straigthened/ground flat by an exhaust shop.

[NoHaveMSG]

These will seal even on a bent or warped flange.

https://catalog.remflex.com/

[Yoshoobaroo]

Originally Posted by NoHaveMSG

These will seal even on a bent or warped flange.

https://catalog.remflex.com/

Have you personally used these?

I've heard that they seal perfectly, but they blow out after a short time. (weeks-months)

[NoHaveMSG]

Originally Posted by Yoshoobaroo

Have you personally used these?

I've heard that they seal perfectly, but they blow out after a short time. (weeks-months)

Yeah. Used them on my old Toyota 4Runner. Was the only way I could ever get the aftermarket header to seal to the block. You need to recheck torque on them a couple times after a few heat cycles on them. Always worked great for me.

[86TOYO2k17]

Could try doubling up on the gaskets. Torque it to spec not just “super tight”

If it’s not making a weird noise you’re trying to resolve, then a small leak at the midpipe to muffler isn’t that big a deal far enough back in the system shouldn’t matter too much, unless it’s making weird noises.

Worst comes to worse Ebay has used ones shipped for 200$ or less

Exhaust shop should be able to fix it though either grinding it down flat, maybe welding on a new flange.

Could try To cut off both flanges and weld on a vband or a slip joint

Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker Could fix it,
But DO NOT apply it to the outside of the flanges it goes directly on where the gasket and flange mate acting as a new second gasket, but fills in uneven surfaces. Typically with gasket
Maker you apply it, hand tighten the bolts wait about 45mins and then torque to spec. Most people torque right away and squeeze out the gasket maker.

[alex87f]

Originally Posted by Yoshoobaroo

One of the flanges is bent.
Take both parts off, measure which one is bent and have it straigthened/ground flat by an exhaust shop.

Will check that out. Thanks.

Originally Posted by NoHaveMSG

These will seal even on a bent or warped flange.

https://catalog.remflex.com/

Seems like a good idea on paper.. but $20 + $110 shipping to France is a bit absurd and I couldn't find other resellers. I can get a stainless resonated midpipe for not much more

Originally Posted by 86TOYO2k17

Could try doubling up on the gaskets. Torque it to spec not just “super tight”

If it’s not making a weird noise you’re trying to resolve, then a small leak at the midpipe to muffler isn’t that big a deal far enough back in the system shouldn’t matter too much, unless it’s making weird noises.

Worst comes to worse Ebay has used ones shipped for 200$ or less

Exhaust shop should be able to fix it though either grinding it down flat, maybe welding on a new flange.

Could try To cut off both flanges and weld on a vband or a slip joint

Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker Could fix it,
But DO NOT apply it to the outside of the flanges it goes directly on where the gasket and flange mate acting as a new second gasket, but fills in uneven surfaces. Typically with gasket
Maker you apply it, hand tighten the bolts wait about 45mins and then torque to spec. Most people torque right away and squeeze out the gasket maker.

Thanks - I'll try separating the flanges, checking for flatness, sandpapering them as flat as I can in case there's debris left, and using leftover JBWeld paste on the gasket, and not outside like I first did.

If the flange on the midpipe is dead, I'll probably replace the whole thing.

[Boccaccio]

I second the suggestion using Remflex gaskets.

The remflex gaskets sealed a stubborn leak between the header-overpipe and overpipe-frontpipe connection.

Pay attention not to bend them, because they are fragile when subjected to bending stress. They compress slightly when you tighten them (torque the bolts/nuts according to Remflexes torque specs) and fill any flange imperfections.

I ordered the gaskets directly from Remflex (Mrs. Diana was my contact) and they provided me with reasonable shipping costs to Slovenia (approx. 40€).

Since I'll be needing another set of their gaskets, we could make a group buy

Cheers

[86TOYO2k17]

Originally Posted by alex87f

Will check that out. Thanks.



Seems like a good idea on paper.. but $20 + $110 shipping to France is a bit absurd and I couldn't find other resellers. I can get a stainless resonated midpipe for not much more



Thanks - I'll try separating the flanges, checking for flatness, sandpapering them as flat as I can in case there's debris left, and using leftover JBWeld paste on the gasket, and not outside like I first did.

If the flange on the midpipe is dead, I'll probably replace the whole thing.

You need gasket maker not Jb weld. Do not use the JB weld to create a gasket.
Gasket maker is more “squishy” it allows a little play for vibrations. JB weld drys and becomes too hard making it almost brittle, it wont hold up as a gasket it’ll end up cracking and leaking again. JB weld is good for fixing small cracks, not mating two surfaces.

[alex87f]

Originally Posted by 86TOYO2k17

You need gasket maker not Jb weld. Do not use the JB weld to create a gasket.
Gasket maker is more “squishy” it allows a little play for vibrations. JB weld drys and becomes too hard making it almost brittle, it wont hold up as a gasket it’ll end up cracking and leaking again. JB weld is good for fixing small cracks, not mating two surfaces.

You're right, probably wasn't the best idea.
I'm of half a mind to confirm that doesn't work, and just bring it to a shop to correct the flanges. Will probably cost me a 100 bucks, but at least that'll be dealt with.