Major leakage at Catback-->Frontpipe. - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

ItsReiko · 10-14-2020, 12:20 AM

Hey guys. I am looking for some help on a big leak where my Perrin catback and Oem front pipe meets. I was changing my trans fluid and discovered this, so who knows how long it has been leaking.

I've never installed any exhaust parts myself, so hoping I can learn some things here for this particular section of the exhaust.
You can take a look at a video of what I mean here:

So a couple things:
1. From some research, aren't these two parts supposed to be held together by some kind of donut gasket with a spring bolt? Mine seem to be a simple flat gasket with fixed bolts.

2. Will I simply be able to remove the bolts and slide the broken gasket out (assuming it's not a donut gasket) and slide a new one in and re-torque, or will I have to undo the whole catback exhaust to perform the fix?

3. Would I have been loosing any kind of performance from this? I've been feeling the car doesn't pull as hard as before in the last couple thousand miles, and I have no idea if that's just in my head. However, I can literally feel air gushing out of this leak with my hand while the engine is just idling. (you can hear @ around 13 seconds)

4. Is it normal for these gaskets to crud up like this so soon? Car has 32k miles in sunny California

Apoc · 10-14-2020, 12:46 AM

number 2. you can buy a new flat 2.5 inch flange gasket from subaru and just unbolt, change and re-torque. There is plenty of room and with the rubber exhaust hangers you shouldn't have to take the catback off.

norcalpb · 10-14-2020, 02:55 PM

The Perrin catback doesn’t use a donut gasket because it features a flex pipe right after the aforementioned flange.

Buy another 2.5” gasket (I like using Vibrant gaskets) and make sure to install it with high temp silicone sealant that you can buy at any auto store.

I apply the silicone all over but remember to tighten down the bolts evenly so that you get a nice snug fit over the new gasket. Whoever installed the exhaust may not have done this, but it looks like you have a leak in the middle of the flange.

I’ve learned recently that it’s good to let the silicone sealant dry over night (no starting the car) for the best possible seal.

Good luck but this shouldn’t be difficult at all.

10-14-2020, 12:20 AM	#1
ItsReiko Member Join Date: Jan 2020 Drives: 2017 subaru brz Location: Cali Posts: 85 Thanks: 13 Thanked 13 Times in 10 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	Major leakage at Catback-->Frontpipe. Hey guys. I am looking for some help on a big leak where my Perrin catback and Oem front pipe meets. I was changing my trans fluid and discovered this, so who knows how long it has been leaking. I've never installed any exhaust parts myself, so hoping I can learn some things here for this particular section of the exhaust. You can take a look at a video of what I mean here: So a couple things: 1. From some research, aren't these two parts supposed to be held together by some kind of donut gasket with a spring bolt? Mine seem to be a simple flat gasket with fixed bolts. 2. Will I simply be able to remove the bolts and slide the broken gasket out (assuming it's not a donut gasket) and slide a new one in and re-torque, or will I have to undo the whole catback exhaust to perform the fix? 3. Would I have been loosing any kind of performance from this? I've been feeling the car doesn't pull as hard as before in the last couple thousand miles, and I have no idea if that's just in my head. However, I can literally feel air gushing out of this leak with my hand while the engine is just idling. (you can hear @ around 13 seconds) 4. Is it normal for these gaskets to crud up like this so soon? Car has 32k miles in sunny California

10-14-2020, 12:46 AM	#2
Apoc Senior Member Join Date: Jul 2012 Drives: Raven FR-S 6M Location: Calgary, Canada Posts: 638 Thanks: 348 Thanked 375 Times in 232 Posts Mentioned: 3 Post(s) Tagged: 1 Thread(s)	number 2. you can buy a new flat 2.5 inch flange gasket from subaru and just unbolt, change and re-torque. There is plenty of room and with the rubber exhaust hangers you shouldn't have to take the catback off. __________________ “The World is Flat” [\|\|•]=(86)=[•\|\|]

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10-14-2020, 02:55 PM	#3
norcalpb Senior Member Join Date: Oct 2013 Drives: 2013 BRZ, 2023 Model 3 Location: SF Bay Area Posts: 2,296 Thanks: 1,212 Thanked 861 Times in 570 Posts Mentioned: 15 Post(s) Tagged: 0 Thread(s)	The Perrin catback doesn’t use a donut gasket because it features a flex pipe right after the aforementioned flange. Buy another 2.5” gasket (I like using Vibrant gaskets) and make sure to install it with high temp silicone sealant that you can buy at any auto store. I apply the silicone all over but remember to tighten down the bolts evenly so that you get a nice snug fit over the new gasket. Whoever installed the exhaust may not have done this, but it looks like you have a leak in the middle of the flange. I’ve learned recently that it’s good to let the silicone sealant dry over night (no starting the car) for the best possible seal. Good luck but this shouldn’t be difficult at all.

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