Hey all! Hope this post gets seen where I posted it. So, I installed an aftermarket exhaust this weekend... finally fixed my exhaust issues. So now I have a complete headers-back aftermarket setup. Originally it just started with a y-pipe rattle I wanted to fix. Next thing I know I've purchased test pipes, y pipe, and the rest lol.

It mated up well enough... save for one main issue: the rubbing. Or touching. With the underbody/frame of the vehicle... I tried to capture this as best I could with photos. I know it might be a little hard to see in the pics... but there are a few spots where it is literally pushed up very tightly against the underbody of the vehicle in ways that I don't think our stock exhaust does?

I don't know if this is a major cause for concern or not... I was thinking about maybe getting some longer/extended rubber exhaust hangers and see if I can reposition it to sit slightly lower? Only thing is, it won't probably fit up to the one final rear hanger on the muffler. It also might look funny if the mufflers are sitting lower than they should look stock.

Thoughts? I also am not entirely thrilled with a very audible raspy sound that doesn't sound healthy lol.... I can't see anywhere it's leaking though... and the sound seems to go away when it's a little warmed up?

 

Those gaskets WILL leak if they have not already.
Next time those come off sand them flat and use metal gaskets.
Autozone sells Mahle multi layer steel gaskets that do wonderful as long as the flanges are flat.

For the NVH, I see the exhaust resting on the bridge(can be bent for clearance), the rest I suggest you try to visit a muffler shop.
The should be able to put spacers between the exhaust and the body then weld brackets in the new position.

 

Thanks, BULL. I was hoping something as simple and cheap as using these extended-length hangers would work (below). Do you have a link to these gaskets you speak of available at a local Autozone? I know Mahle makes quality engine components...didn't know they made exhaust gaskets too. All the pipes were brand new and they were pretty flat already... are you saying I should have still sanded them down? And only use these MLS gaskets? No copper spray or RTV at all?

Yeah, my issue is certainly with the rasp/drone and rubbing. It's so bad now I can't tell what's worse. Maybe with those polyurethane exhaust hangers, the whole setup won't flop around so much when I'm driving.... I guess I don't fully understand what you're saying about an exhaust shop being able to put spacers in between the exhaust and body... Would these just be blocks of metal they weld to the frame or body?

I really hate the raspy sound. It could just be worse because half of the y-pipe is literally pushed up HARD against parts of the underbody. What a crappy fitment - poor design - poor QA - whatever.

What I'm REALLY starting to be concerned about now is this exhaust smell in the cabin. I've had plenty of cars with cat delete exhaust setups, but I don't recall ever feeling sick to my stomach from the exhaust smells INSIDE the car while driving on the highway at 80mph. Jesus. I made sure all the bolts were tight and lined up correctly. These are all brand new pipes that didn't have any signs of leaking or cracks when I installed them. Unless I royally jacked up the gasket flange part(s) somehow.... or my stock headers are leaking now? I don't know, it sounds much worse coming from the passenger side. Like the wheel-well area and right underneath my feet. Probably cuz that's where the Y-Pipe is trying to become one with the underbody of the car. Can't possibly be good.

I can't live with this rasp nor the rubbing but especially not the fumes. It's so bad I parked my car outside (not in the garage) tonight because I want that smell to sort of get aired out. Cracked my windows too. Hate doing that in the winter when snow is being called for tomorrow here in Colorado lol.


12MM Urethane Exhaust Hanger Extended Length




Or any of these other extended ones where you can select-a-hole it seems lol:

 

Even on new exhausts flanges can be warped.
Why in specific to the G/Z exhausts? It's usually due to the thin stainless used, they are mocked first the full beads are run afterwards.
Metal warps upon welding so any manufacturer that doesnt check for flatness after welding is just not proper quality control and this is common, just over expectations from our end.
Lastly is flange desing, if you pay attention to the OEM Y pipe the ID of the hole is pretty small meaning the flange has plenty of clamping material however on aftermarket exhaust you loose a lot of this are due to size increase which means even less material to clamp. Add this to warped flanges and leaks here we come.

Properly flattened flanges with a MLS/Crushable gasket will be the best attempt at this fix. I'm a firm believer of the red/orange RTV but usually the amount of RTV a flange takes up usually tells you if you'll have a problem in the future.
I noticed you're running composite gaskets in the Ypipe and these are notorious to deteriorate quickly.

PS: check what type of cats/test pipes you're using - OEM uses a crush style donut ring that does wonderful at preventing leaks as long as the ring is new/ish. If your cats/tespipes dont then some sanding will be required on the cat flanges as well, this one is a bit harder to do due to their location and having to work around the manifold stud. I've gotten great results with 80grit flat foam pads used to flatten walls, etc.

Take your time, a common trick I use is the Sharpie trick, once you believe they're flat, color the whole flange face and sand again. Uneven areas will be revealed as you start sanding again. The idea is to be able to remove almost all of the marker with the flat sandpaper. Once you have you can consider it FLAT.

Here's the gasket

 

Thanks for the visual. I assume what you meant by "they are mocked first the full beads are run afterwards" was something to do with the welding process. Once again I just struggle to follow your posts sometimes. Maybe it's the grammar/syntax or sentence structure. I'm sorry.

I don't know what "flange desing" is, but I assume you meant "design" i.e. the way the flanges are designed.

Yes I'm running the composite type flanges with a thin layer of the red high temp RTV. This has never failed me on other cars I've had aftermarket exhausts on... and the exhaust and gaskets and RTV are brand new, about 5 days old now? But I think you may be onto something because I can't even breathe with the smell of exhaust fumes INSIDE MY CAR. This is ridiculous.

Problem is, I live in a very blue, emissions-controlled area of the country... I fear a challenge to find a shop that can diagnose and repair where the leaks are coming from since I deleted my cats and am running test pipes in their place... IME, the last shop I took it to quoted me $6000 to replace all the exhaust with OEM blah blah blah "because emissions". Which I think is horse SH*T lol.

I would hope the same shop who you say should be able to bend exhaust or make brackets (???) to help with the rubbing should also be able to sand down flanges and use those MLS gaskets?

Wish me luck. Just being in my car makes me sick and want to puke from the insane exhaust smell pumped into my face every time I start the car. Ugh.

 

You could also try the trick a member recommended which is to use a vacuum cleaner into the mufflers and some soapy water to the flanges to see if any are leaking.

Damn grammar errors but yes flange design. It's been documented in the past and many folks including myself went through this. The issue with the perforated gasket is the layer in between is exposed to the elements and will deteriorate over time. MLS gaskets dont deteriorate.

 

Alrighty wish me luck... just going to take it to an exhaust/muffler shop locally tomorrow.

If anything, I'm guessing it needs the flanges to be cleaned and then those MLS gaskets used and everything torqued down correctly.

Oh and the pipes need realignment since they're smushed against my underbody.

The whole exhaust system feels like it's about to fall off when I'm driving. And all the bolts are tight.


Wish me luck they don't want $6000 from me, which is half the damn car's value. lol

 

I've also have had great results with these thick gaskets for uneven/warped flanges.

https://conceptzperformance.com/czp-...al_p_63530.php

 

Welp, sure enough, once again another shop won't touch my car because I have test pipes in place of the OEM cats.

We live in a very blue, emissions **** area.

I even asked the shop if I could just pay him to put my factory cats back on and he said no, he's not allowed to touch used parts.

FML.


He said a pair of OEM cats was priced out for me at $4300. I guess that's better than the other shop that wanted $6000.

I'm sick of taking my car to multiple shops and leaving it there for 1-2-3 days and wasting $$$ on Uber rides all over town just for the shop to call me and say "sorry buddy can't help ya, you need 400 catalytic converters! we gotta save the planet!"

He also said those composite gaskets work just fine and exhaust systems don't always require the MLS gaskets BULL was harping on.


It was SUCH a giant PITA to access those bolts on the cats.... and the exhaust shop said that's where I'm having the leak... from the headers to the cat and the cat to y-pipe. He said the test pipes are terribly designed. Guess that's my fault for going with ebay crap.

Maybe I can purchase a set of nicer "test pipes" from a reputable brand i.e. Z1 that WILL fit and WON'T leak?

Just the thought of having to access those "demon" bolts again UGH FML lol

 

I swear, exhaust systems or components pricing are simply way out of control. Granted, they've sort of always been that way... but it's insane now.

Serious question, who in their right mind thinks $2000+ is a fair price for a pair of "high flow" catalytic converters lol. VQ37VHR Sport Catalytic Converter



Give.

Me.

A.

Break.

 

Thank the EPA for that.

 

Happy happy joy joy lol.

Ordered some "name brand" test pipes from Z1. We'll see if they fit better than the eBay ones. I just liked the eBay ones cuz they were cheap and resonated. And I don't want to pay $700 - $2000 for some "high flow" cats lol

 

Hey Bigspoon, I try to give the most realistic and experience driven advice as many times as I possibly can.
This is documented info and I see exhaust leak threads left and right on many platforms with many of them finding peace with flat flanges and metal crush style gaskets.
I have them on my car, I have them on my engine stand. I believe I even have pictures of how OEM and HFC flanges warp.

Shops will always recommend whatever they think will work however many times you see the forums knowing about a specific aspect of the car that the typical shops dont and this is because these shops dont live, eat and breathe these cars nor deal with the ridiculous issues that these can give on a daily basis. Many times they will give ridiculous prices just to scare the customer away.
I suggest you try to find a local member in your area that's tech savvy, it will be the way to go.

 

Yes sir, thank you for all your comments and feedback, and advice. I do appreciate it! I appreciate everyone here and this whole forum/community. We're all here to help each other out and engage with fun car modifications

Don't know what you mean about finding a local member who's tech savvy? I'm pretty tech savvy: I build desktop PCs for fun, I know a little bid of Python coding, I'm smarter than the average bear with most things tech. I'd like to think I'm pretty savvy! Unless you're talking about vehicles? If so, I guess my years of experience working on cars since about age 17 (I'm 36 now) is worthless as it has done nothing to make me any more "savvy" than just some average random dude walking on the street who doesn't even know the difference between a manual and automatic transmission. That guy probably knows more than me. No, I didn't entirely rebuild 2-3 engines (mine and friends, with friends) of my 1998 Jeep Grand Cherokee w/ the 5.9l (only year) that we stroked, rebuilt, and supercharged. I mean, the only thing I've never done before is transmission work. And air conditioner or power steering repairs. Other than that....

I do hear you 100% on shops giving ridiculous prices to customers so they "just don't have to deal with it". It's frustrating as a consumer to try and figure out what a shop should, could, or would charge for any given repair job when you call 3 different shops and get 3 WILDLY different prices.

The biggest problem is the EPA and the increasingly bluer & bluer politics of this state = difficulty getting ANY shop to work on ANY car that doesn't have catalytic converters. And when I talk to some shops, it's not that they care, mind, or don't know HOW to work on exhaust systems without cats... it's just that they're terrified of getting fined or whatever by the good old over-protective government...

 

I'm sick of the exhaust leak(s). Literally. This AM I wanted to scream out of frustration as I'm sitting in my car warming it up (blizzard snow dump today here in Denver). Why? Because the exhaust smell is worse INSIDE the cabin than outside the car. WTF?! Lol. I'm alternating between sitting inside while it warms up to brushing off snow and scraping ice outside the car. As you're sitting inside, it's like the exhaust smell/fumes are being directly pumped into your mouth/nose/brain and make me want to puke repeatedly.

It's also embarrassing when all your clothes or anything inside the car gets exhaust fume soaked and you get to take that lovely scent with you, wherever you go next.

So big middle finger time to these exhaust leaks! You wanna play games, Mr. Exhaust? I'm done. New test pipes (brand name from Z1, not eBay knockoffs this time), MLS gaskets (per BULL), and ARP hardware. You might call it overkill. Once those flanges are nice and flat and matching, these ARP bolts and nuts will hold that flange together something fierce. Nice and tight. Heat treated, strong AF hardware. No more games. Also going to ceramic coat and then use DEI titanium exhaust wrap on the test pipes. Topped off with metal ties and hi-temp silicone spray coating.

No more games. I don't want this to leak. Ever. Gotta wait until this weekend though... friend coming into town and we're going to rent one of those DIY garages with a lift. Should make working on the exhaust a little easier than up on jack stands in my small garage.