Since I've installed my Comptech header this weekend, I have been subject to the annoying 'rattle at idle'. It is loud enough to drive me crazy if its going to happen on a consistent basis, so its come time that we try to figure out what the heck is causing it!

My first diagnosis: after installing it, I noticed how the primary O2 sensor sat extremely close to a piece of the lower subframe. After re-inspecting it after driving a few days on it, the two are now touching, indeed the O2 sensor is resting on it when the car is off. This is the fist thing I think could be the cause of the rattle.

If I wanted to isolate the two, what would be the best way to do so? I want to put some kind of rubber in between them so its no longer metal-on-metal contact. However, the O2 sensor gets extremely hot while in use, and I don't want rubber melting on it and fouling it up. Does anyone have any suggestions for material I should use?

Also, I welcome any other comments from Comptech header owners around what they think could be the cause of the rattle.

 

First, I suggest some pics at your earliest convenience.

Second, I'm not sure the rest of us have experience this same clearence issue on their O2 sensor.

Thus far, I've been rattle free since the summer time. It came and disappeared on me.

 

This may be off topic. But do you still have the Top speed header? Care to give a brief comparison on the two?

Thanks...

 

The answer to those questions should be "no" ( ) and "yes"

and, lastly,

 

Pics will have to happen late tonight, its snowed a little bit today so I took the 4x4.
JRock, I'll get to that soon. And no, I don't have the topspeed anymore.

 

Looking forward to more info on this, as I plan on adding the Comptech Headers and RT CAT to my CT Exhaust soon.... and want to make sure I install in right and make any modifications etc nessisary.

 

I have the Comptech I/H/E setup and had a problem with a rattle for a while. I thought it was the header as well until I took off the exhaust and then re-installed it. This time I cleaned the flanges really good with sand paper and WD-40 and re-installed the exhaust. Now, no rattle. Good luck with your search. I would suggest checking the seal at the flange to the CAT. I know it uses a gasket but something may be causing it to leak or not seat right.

 

What happened to it? Did it break? Disapointed in the header? Thanks.

 

Neither, I just got the Comptech. I can change a header in 2 hours, so its not a big deal to swap.

Please keep this thread on the topic of the comptech header related rattle. Again, I will post pics of what I noticed later. In the meantime, I'd still like any suggestions for materials I could use to isolate the O2 sensor that won't melt.

 

Long overdue pics... notice the subframe block sticking down right next to the O2 sensor.

 

where does your rattle comes from? i still have the noise but when i listened it carefully that resonating sound is coming from the rear section of the car. for me i think its excessive vibration caused by one piece design of comptech header creating resonance at the end of exhaust piping.

 

i wish i could fix this noise before the summer comes since it only comes on when the a/c is on.

 

Doesn't the OEM header have spring loaded bolts between the header and cat? I wonder if you guys could use something like this on the header.

 

Yeah, it's more louder in the rear seats than the front. I agree it's likely the exhaust piping acting like a tuning fork, vibrating at low rpm. Also likely why it's far more noticeable on a 5AT as we idle in gear. If there were a way to increase idle by say 50-100 rpm, that would be a work around, but that apparently can't be done. I don't think there is any way to fix it. Didn't someone try polyurethane hangers to no avail? I've surprisingly gotten somewhat accustomed to it. I think you either have to live with it or get rid of it.

 

i thought of that too. but i believe stock spring bolts don't fit right?

 

raising up idle upto about 800rpm was one of the way, but dealers won't do it. thats why whenever i hear the noise i shift it into neutral.

 

The spring loaded bolts are used within the header itself as it's a two piece design. The bolts used to connect the header and cat are just regular bolts. The Comptech header being a one piece design can't utilize those bolts.

 

The spring bolts on the stock header hold the exhaust manifold to the a-pipe. I'm noticing this rattle is NOT a/c dependent for me, as I've been driving around with the hvac system completely off and the windows open for 2 days now.

So, what could I wrap the O2 sensor in or place between those two pieces as a start?

 

Is the block hanging down an new addition to your model year? The 04 doesn't have that. If that's the case, Comptech didn't test fit the header on the newer model.

 

Interesting, I hadn't noticed that difference before. The block is definitly missing from your car, it might be an '06 addition.

Here is a pic from my topspeed header install:




It looks like the Comptech O2 bung is positioned closer to the flex pipe in comparison:


Still no ideas about wrapping the O2 sensor with an insulating material? I just don't know what to use.

This might only be a part of the problem, but I would like to isolate them.
JTso, it looks like your DC O2 sensor is also positioned a bit further from the flex pipe, where my subframe block is.

Man, I hope I don't have to move on to my 3rd header.

 

insulation the O2 sensor is not a good solution as it doesn't actually correct the rubbing problem. I would simply drill another hole and install an O2 bung a couple of inches from the flex pipe, then plug the first hole. An exhaust shop can do it under 30 mins. Btw, what is the function of that block hanging down? Can it be removed? If so, that would be the easiest fix without messing with the O2 sensor.

 

Very interesting... I've got a CT Header I'm going to be putting on this week, and I've got an 06 as well... haven't looked under my car yet to see if that block for myself... never really thought to look for it, but I will check it out tomorrow. Most likely if Reach has an 06... than mine will have it as well


What do you think that block does? From the pics it almost looks like just an extra piece of metal? Doesn't seem to really be supporting anything or connected to anything else? Wonder if it can just be taken off?


I'll check under my car tomorrow and see i guess. Hopefully this won't be an issue with installing my headers.

 

It's not A/C dependent for me either, sometimes it's there, sometimes not. However, do you only notice it at around 700-800 rpm? If you are idling, hear the noise, and then put the car in neutral, does the sound go away? If so, that's the "normal" Comptech sound and not likely related to the O2 sensor position.

 

Yes, you've described it exactly. I'll have to get the car up on stands again sometime soon and idle it and see if I can reproduce it while running. I do also want to examine the subframe block further, I'm sure its there for a reason.

 

for me it was only AC related, without the AC on i didn't hear it

 

Oh yeah, that's right! As you tell, it's been quite awhile since I've had the stock header on

If you guys found some custom spring loaded bolts, do you think that would help to reduce the vibration?

Just trying to throw some solutions out there for you guys, I'm running a DC Sports/JTso A Pipe header.

 

OK, here's another idea: Could it have anything to do with the funny compression gasket Comptech supplies for use with the header? I did use this between the header and cat. Topspeed supplied a full-flange-size paper gasket for use at this joint, and I don't know what DC supplies, if anything.

For those that don't know, Comptech's gasket is basically a metal o-ring with a split down the middle. It is exactly the size of the opening on the cat, so when the cat matches up to it and the bolts are tightened, it crushes down some.

Are there any flange-sized gaskets that I could try as a replacement, like a napa part or something that is the size of the header-to-cat flanges? Basically I'm taking this idea as an extension of the moda_way idea to use napa gaskets between the cat and exhaust.

 

Changing the gasket at the flange side does not change anything on the O2 sensor side. Therefore, it will not fix your problem.

 

I agree with that sentiment, but consensus seems to be that the O2 sensor alone is not the problem. People with all model years are having this rattle. I just want to investigate anything unique to the Comptech header that could be the cause.

 

Check your hoods too. My rattle comes from where my hood or hood latch. I haven't had time to fix it, cuz it doesn't really bother me right now.

 

mine definitly isn't that far forward. when its quiet, it feel like its right below me, at the header/cat area. when its obnoxious, it feels like the whole exhaust is resonating behind me / at the rear of the car, perhaps under the rear seat or just a little further back.

I've also noticed it is so much louder inside the car vs outside.

 

I know, just adding to the possible sources for everyone.

if it weren't for the hood rattle, it would just be a vibration for me at about 700 or 800 rpm. I don't get any rattle from the rear of the car.

 

DC header also uses the OEM style metal O-ring at the flange without rattle. You could try removing the rubber hander for the header and see if that makes any difference.

 

When I was trying to diagnose the problem, I just put the car in drive on a level surface and put the parking brake on and looked underneath. As the rpms drop slowly to idle you can easily see the whole header-cat-exhaust assembly increasing vibrate, from barely noticable at around 1000 rpm to seemingly excessive at around 700 rpm, and that's when you can hear the hum. It's not hitting anything or it would be a metal on metal tap. I think it's just the resonant frequency of the assembly.

 

Reach: Have you had any luck trying to fix this problem?

 

Just took a look under my car and the block is present. It's an 05. Maybe it's 5AT related.

 

Does the block serve any purpose? Is there anything connected to it?

 

I would assume it serves a purpose, but I have no idea as to what. I should have been more specific, I knelt down and looked under the car, I didn't have it jacked up, I don't know what it's connected to.

 

mine too

 

Flipping thru Helm's manual I saw two things that it might be, front subframe rear vibration damper or 5AT rear mount stop. Those were the only U shaped bracket looking pieces that seemed to be in that area, that I could find. I'm betting against the damper. The 5AT rear mount stop is mentioned a few steps before and after, removal and installation of the A-pipe, in the removal and installation of the automatic transmission procedure, respectively. Drawing isn't exactly clear however.