I recently had the Borla cat-back dual exhaust system installed on my 03 4runner V8 by a local shop. Everything went fine except that when I start the engine from a cold start, I can hear a loud rattling noise coming from underneath the truck. Once the engine is warmed up, the rattling goes away.

If I tug on the exhaust pipe near the connection from the muffler to the cat while the truck is running, the rattling sound goes away. I was thinking the bolts connecting the cat to the new exhaust weren't tightened down all the way, but they were (they were actually tightened down all the way to the end of the threads on the bolt). I'm not sure if the installer re-used the factory cat gasket on the new exhaust. Could that be the problem? Any ideas on what the rattling could be from? Thanks for any help!

 

I'd take it back to the shop that installed it and make them check it out.

 

Likely touching a heat shield on the underside of the truck.

 

I took mine to the dealer with probably the same rattling noise. The tech writer said the 'resonance' noise is similar to two other vehicles they brought in to compare to mine. How, I asked, when I have the dual Borla and these were oem vehicles?

Mine goes away after its warmed up. Maybe just the aluminum needing to expand until normal operating temp? It only happens whn I am in "D" with my foot on the brake. I don't think I will have any luck getting the dealer to fix it, it has already been stamped, "Could not duplicate".

BTW..I bought my Runner with the Borla from the factory/port.

 

Ask him if he is missing a socket

 

[QUOTE]Originally posted by Sac State
[B]I took mine to the dealer with probably the same rattling noise. The tech writer said the 'resonance' noise is similar to two other vehicles they brought in to compare to mine. How, I asked, when I have the dual Borla and these were oem vehicles?
Mine goes away after its warmed up.

I could be wrong but could this be the same rattling that Mish is getting now starting on your truck ..just a thought..

 

Well, it looks like I was able to fix the rattling problem myself. Last night I removed the two bolts connecting the muffler to the cat and just re-seated the flange and cat gasket. Then I put the bolts back on, tightened them down all the way and that was it. This morning I started up the truck and no rattling sound! Hopefully the rattling will be gone for good.

 

[QUOTE]Originally posted by Sil23

Quote:

[i]

I could be wrong but could this be the same rattling that Mish is getting now starting on your truck ..just a thought..

I've got the V8, Mish has the 6, its more exhaust related than lifter/valve related. I will try checking the gasket, flange and bolt torque.

What ft/lbs of torque did you apply to the bolts??

 

Sac State,
The bolts that connect the muffler to the cat don't have a torque spec (as far as I know). I couldn't get my torque wrench to fit underneath the truck as I was bolting them back up so I just used a smaller socket wrench. The bolts only have thread on them for about 1/3 of the way up so they come to a stop before you can really tighten them down. I'm assuming they did that so you can't over-tighten them.

 

This sound you guys are talkin about...is it when you first start the truck it sounds like its right underneath me, a metal vibration sound, but then goes away after warming up...i checked all bolts and everything is tight so I have no idea what it is

 

LIVE4SWELL,
Yeah, that's exactly the sound I was getting when the engine was still cold. I'm pretty sure it was coming from the connection between the cat and the muffler pipe. I fixed it by taking out the two bolts and just playing around with the cat gasket and spun the cat flange (looks like an o-ring with two bolt holes, on the end of the muffler pipe) around 180 degrees, then re-tightened the bolts. After I did that, the rattling sound went away and hasn't come back since.

 

ok, thanks a lot...i guess i will do the same...hopefully it works for me....its weird because the sound wasnt there when it was first installed , it started about a week after....who knows

thanks for the help

 

Has the rattle come back for you? I tried reseating the flange and still have it...maybe i should play around with it more but i am not sure if the rattle comes from there or the stock cat...i was underneath with my dad revving and it seemed like the cat right there was the source of the rattle as in something inside is loose...i guess i will mention something to the dealer and see what they say if i cant fix it...hopefully they dont blame it on installing the bolt on cat-back

 

Nope, still no rattle since I fixed it last time. I may have gotten lucky when I re-adjusted all the bolts and gaskets so that everything fit snugly. I would keep trying since it sounds like you have the same rattle as me.

One thing I found when I had the rattle was when someone else revved the engine while I was underneath it, I could stop the rattle noise by pulling on the pipe near the cat/muffler connection. If you can make it stop by doing that, I would think you'd be able to fix it by doing what I did. If not, the noise may be coming from somewhere else.

Good luck!