Loose, Metallic Rattle from Exhaust @ 2k Revs

redevil01 · Post by **redevil01** » Mon Apr 27, 2009 3:38 pm

I have a HKS dragger exhaust on my fto and I made a post sometime ago detailing my frustration as I suspected that some punk had thrown a pebble into the exhaust system and it was causing an annoying rattle.

In the last few days this rattle has been getting louder, and now sounding more and more like an actual exhaust malfunction than a simple pebble in the exhaust.

Symptoms:

When I rev the car, in any gear, between 2-3k revs I get a loose, metallic rattle coming of from the exhaust system at the rear of the car.

Iâ€™ve done some research on the net and some forums have said itâ€™s a loose timing belt??wtf ??

But a mechanic friend of mine said it could be loose rubber in the exhaust system thatâ€™s been worn..

I have no idea, anyone had a similar experience !?

Post by **Bennoz** » Mon Apr 27, 2009 3:45 pm

Could be any number of things.

Could be the metal sheild around the cat.

Could be a failing cat converter (internals are hanging out & being blown around the inside of the pipe)

Could be a corroded head on the 02 sensor

Could be a busted hanger & as a result, the exhaust is hitting on something.

Could be the heat sheild coming loose thats sits underneath the spare tyre well.

Could be a hole!

Too many things to predict in other words. The only way your gonna find it is if you get it up on a hoist & have a look.

Jamie · Post by **Jamie** » Mon Apr 27, 2009 8:11 pm

My money is on the cat!

If you want to save some money just get under your car armed with a rubber mallet and tap along the exhaust untill you find the source of the rattling. Will be a lot easier if the car is cold too

redevil01 · Post by **redevil01** » Mon Apr 27, 2009 10:48 pm

I gave it a modest beating with the home delivered Saturday Age news paper. It sounded like it was comming from the cat, but i didnt really inspect for too long as it was raining..the odd bit to me is the fact it only goes of at 2k revs, almost systematically..im having it checked out this week on the hoist at an exhaust joint..Thanks guys!

redevil01 · Post by **redevil01** » Tue Apr 28, 2009 2:08 pm

Took it to the exhaust dudes today and they were alittle ambigous about what the probelm is and what the solution could be.. however the mechanic said that he could see a new cat was installed and suspects a unit of the old cat had slid down the exhaust and now is stuck in the rear of the muffler and the only way to fix it is to get a custom made muffler (they dont have new ones that fit the fto build) and install that one.

..450 dollars, dont know if that sounds about right but i wasnt sold by the idea, im sure theres gota be another way around it.

mr-charisma · Post by **mr-charisma** » Tue Apr 28, 2009 2:17 pm

redevil01 wrote:Took it to the exhaust dudes today and they were alittle ambigous about what the probelm is and what the solution could be.. however the mechanic said that he could see a new cat was installed and suspects a unit of the old cat had slid down the exhaust and now is stuck in the rear of the muffler and the only way to fix it is to get a custom made muffler (they dont have new ones that fit the fto build) and install that one.

..450 dollars, dont know if that sounds about right but i wasnt sold by the idea, im sure theres gota be another way around it.

If they are quoting you $450 just for a muffler, then boy did they see you coming.. just get an el cheapo cannon & throw it on if thats all you're after..

If I've gotten it wrong, and they're quoting you on a cat-back .. $450 sounds like a backyard special ..

IMO though don't even bother doing anything to the exhaust unless you're going to upgrade it to 2.5" mandrel bent piping .. mild or stainless is up to you..

All they probably need to do is take off the cat back section of the exhaust & empty out whatever is rattling around in there..

Jamie · Post by **Jamie** » Tue Apr 28, 2009 8:51 pm

I think you will find the reason it only rattles at 2K revs is because the cat/muffler are resonating.

I had a cat that did the same thing. would only rattle at a certain rpm. As it broke down it did begin to rattle more and more though. This is when it gave me the sh*ts and I replaced it.

Since the cat looks fairly new it is possible that some of the cermaic has broken away and ended up in the muffler. I would take it to another exhaust shop and get them to replace the muffler. Any reputable shop will have a generic muffler in stock and should only take them 15mins to install. I wouldn't pay more than $200 fitted.

arkoso · Post by **arkoso** » Tue Apr 28, 2009 9:27 pm

Jamie wrote:I think you will find it only rattles at 2K revs.

I had a cat that did the same thing.

ft04me · Post by **ft04me** » Wed Apr 29, 2009 12:07 am

I too have this problem with the same exhaust... Mine is really bad but did the same thing as u describe.. It gets annoying and really embarrasing as it is really loud and noticeable from outside the vehicle... It sounds like the car is gargagling...

Post by **Bennoz** » Wed Apr 29, 2009 9:11 am

redevil01 wrote:the only way to fix it is to get a custom made muffler (they dont have new ones that fit the fto build) and install that one.

..450 dollars, dont know if that sounds about right but i wasnt sold by the idea, im sure theres gota be another way around it.

They certainly have seen you coming

Any bloody muffler can be put under there. I'd be heading to another exhaust shop.

redevil01 · Post by **redevil01** » Wed Apr 29, 2009 5:14 pm

I would be happy to replcace the HKS muffler for a stock fto muffler, however i remember when i bought the car i parked it next to my friends fto (94' gpx, mines 95' gpx) and i compared the muffler and piping under the car.. from what i recall the HKS muffler and stock muffler are not direct swap outs, thats one reason why i thought a custom made muffler sounded legit..

Im seriously hoping its just a loose peice of junk thats not fundamental to the operation of the car that i can just shake out! ..then re-attach after.

I've made arrangments to see another exhaust outlet on the weekend (friend of friends), im planning on taking the muffler off in the workshop and giving it a good shaking! dont know how much luck ill have givn the plates inside the muffler.

ft04me, have you had yours diagnosed, like do you know what is causing the sound?

ft04me · Post by **ft04me** » Wed Apr 29, 2009 5:41 pm

hey.. Haven't had mine checked up but I highly suspect that the cat is the culprit.. Where did u take yours?

redevil01 · Post by **redevil01** » Thu Apr 30, 2009 3:52 pm

I took mine to two joints now Glen Waverly Exhausts (450) & Dany Exhausts which i got quoted today on the way to work.

I stopped of at Dany Exhausts and got quoted 350.00 for a new Magnaflow muffler (not sure which one though) fully installed.

http://www.magnaflow.com/02product/shop ... in&id=8122

I spoke with a mate whos friends are part of the Street Supremacy car club, and he advised most club members gets their work done there cos their real cheap and do the job right..

..i dono why but i keep getting quoted 300+ for the dam job and parts and in previous posts 200 was advised as the max i should be paying...i must have rich kid written on my forehead!

Im lead to believe that as the exhaust is a pass through, if something was loose inside it would have fallen out by now so it looks like a replacement is inevitable.

PS>
Charisma, at this stage i dont think ill be changing the exhaust as i saw under the car that mandrel 2.5 piping is already installed. I feel that the exhaust and HKS muffler came as a unit and affraid of performance loss if i attached a Magnaflow onto the existing piping.

FTEvolution · Post by **FTEvolution** » Fri May 01, 2009 8:16 am

Jamie wrote:My money is on the cat!

Me too!

Maybe not...

redevil01 · Post by **redevil01** » Fri May 01, 2009 2:00 pm

When you guys say cat, do you mean a piece of the cat has broken of and slid into the muffler ...or do you mean that the noice is been caused by the cat itself.. but the noise is amplified/resinating in the muffler..??

Post by **I8A4RE** » Fri May 01, 2009 2:20 pm

Mate it could either, inside the muffler there is what are called baffles. they could of broken and caused this noise. Inside the cat is a honeycomb looking material that breaks down over time. It could also cause this noise.

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Jamie · Post by **Jamie** » Fri May 01, 2009 10:11 pm

As Simon said it could be either. Either way it is still going to be the cat causing the problem.

What I meant by the cat resonating is...say part of the substrate in the cat has broken away but is still stuck in the cat. As the exhaust gas passes through, it will reach a point where it causes that peice that has broken away to vibrate. This is the sound you can hear assuming that it is the cat that is your problem. As the exhaust gases flow at a faster rate it becomes forced up againt the back of the cat therefore the rattling stops. Hope that makes sense