Mazda3 Forums banner

Brief How-to: Downpipe removal

49612 Views 32 Replies 20 Participants Last post by  gpower07ms3
Just thought this would help a bit, at least to fellow forum members, to shed a bit of light to downpipe disassembly. I compiled this short how-to about 2 months ago, but never posted it. Anyhow, I hope it helps. If you have any pictures or comments/corrections to the walkthrough below, feel free to post them and I'll edit them in.

Again, I compiled this quickly about 2 months ago so it may be a little bit incomplete.

The following is a short how-to guide on how to install the Cobb Downpipe on the Mazdaspeed3. I wrote the folliwing to supplement the instructions that Cobb releases with the downpipe, unfortunately the cobb's instructions do not come with pictures. I didn't take too many pics during disassembly from stock, so most of the pictures that I took for reassembly were used to illustrate some of the steps. The how-to may be also used with other downpipes.

[size=8pt]Use & Disclaimer:

  • Please do not cross-post this how-to guide / walkthrough and its content (pictures, textual information, etc) to any other forums or boards outside of without first requesting & gaining my permission.
    This brief how-to should not be used as an all-encompassing walkthrough. It is simply a short description of my procedures for removal & installation, and I am not responsible for any damages or injuries that may result.
Tools needed....
Jack & jackstands
Ratchet (3/8", and 1/2")
torque wrench
breaker bar
O2 sensor remover (crow foot)
10mm, 13mm, 14mm and 17mm sockets (6-pt sockets) & a 2", 4" extension
12mm, 13mm, and 14mm box-end wrenches
penetrating fluid & torch (if needed)
needle-nosed pliers

1.) Remove top mount intercooler.... If you are using the stock TMIC, remove the TMIC cover by removing the (2) 10mm bolts. For the intercooler core there will be (3) 12mm nuts holding the intercooler to the top of the motor; there will be (2) at the front and (1) at the back. Next, unbolt the blow-off valve by removing the (2) 10mm bolts [circled in yellow]. Next loosen the clamps on the rubber hoses using a 10mm socket. Now the intercooler should be ready to be lifted off.

2.) Optional....Remove foam/foil heatshield mounted to the firewall by removing the two plastic nuts and sliding it up and out.

3.) Unclip wire loom from black black bracket. Also, unbolt the power-steering line from the bracket using a 10mm socket. Gently move both the wire loom and PS line to the side.

4.) Using an 8mm socket remove the (5) bolts that hold the upper heatshield to the exhaust manifold. Slide the heatshield towards the firewall. Position the heatshield like shown in the second pic, this allows for easier access to remove the rear intercooler mount bracket. You will find it hard to pull the heatshield out of the engine bay w/ the intercooler mount there.

5.) By moving the heatshield out of the way you can now remove the rear TMIC bracket from the block. To gain more access to the (2) bolts that hold the mount to the block, we first have to disassemble the brackets from the intercooler mount. Remove the power steering line bracket from the mount using a 10mm socket.

6.) Next, grab a 13mm socket and remove the (2) bolts holding the mount to the engine. I remember having to use a 13mm box-end wrench to remove the bolt that is straddled by the exhaust manifold.

6.) Using an 8mm socket, remove the (3) bolts and remove the lower heatshield from the exhaust manifold

7.) Unclip the lines to the first O2 sensor from the downpipe heatshield. There should be one spiral clip and two pinch clips that hold the O2 sensor wire as it snakes around the downpipe. Remove the O2 sensor using a 7/8" oxygen sensor removal tool. I used a crowfoot type tool. Soak the threads to the sensor by spraying penetrating fluid under the O2 sensor 'hat'.

8.) Remove the (5) nuts that hold the downpipe to the turbo using a 14mm 6-point socket and various extensions. Be sure to soak the nuts w/ PB blaster before attempting to remove the nuts. Also be sure to use a breaker bar to make removing them easier. I had access to an impact gun, just in case I needed it, but the breaker bar was more than sufficient. Also my car only had 7000miles on the odo at time of disassembly, so the nuts weren't seized on the studs. Temporarily re-install 2 of the top nuts to hold the downpipe in place as you continue disassembly under the car.

9.) Lift the car and place the car on jackstands. Remove the mid-chassis bracing by removing the (8) bolts using a 12mm socket.

10.) Remove the chassis bracing just behind the front crossmember. There will be (4) 14mm bolts and (1) 10mm bolt.

11.) Disconnect the O2 sensors from the ECU harness. Sorry for not having a pic of the sensor location with the stock midpipe in place. The only pic that I have that are useful are of the tunnel w/o the downpipe, but at least it'll give you a general idea of where to look. Follow the oil return line from the oil pan to the bottom of the turbo. The connectors circled are the two connectors to the first O2 sensor (blue & grey and the black connector). The second O2 sensor, which is not in the picture, is to the left of the first O2 sensor connectors (grey connector). Remove the first O2 sensor from the car, and set it aside in a very safe place.

12.) Remove the (2) 14mm spring bolts between the rear of the midpipe and the main exhaust tube. Then remove the (2) 14mm bolts that hold the midpipe to the stock downpipe.

13.) I chose to remove the second O2 sensor w/ the midpipe off the car. Once the sensor is disconnected from the main harness, slide the hanger rods out of the rubber exhaust hangers and remove the midpipe from the vehicle. Once off the vehicle you are free to try your hand at removing the second O2 sensor.

14.) Now go back under the car and remove the (2) 14mm bolts from the factory downpipe to the engine mounting bracket.

15.) Remove the (2) 14mm bolts which hold the bracket to the engine. I recall the outboard bolt being the only one accessible w/ a standard 3/8" ratchet & socket, so remove that one first. The second one I loosened w/ a standard 14mm box end wrench. Once loosened it allowed me to pivot the bracket slighty enough that I could remove it w/ a ratchet.

16.) Remove the two bolts temporarily hold the downpipe to the turbo, that we re-installed in step #8. You will need to rotate and pivot the downpipe to get it out, so try not to tear up the foam heatshield from the exhaust tunnel too much. I had some trouble w/ the downpipe heatshield snagging/catching in a few areas. So i took my 10mm socket and started to remove some of the heatshield bolts, thereby allowing me to move the downpipe heatshielding around to slide it out. Once you have everything out, you should have a parts pile that looks like the following...

Now that everything is removed, just work backwards to reinstall the new downpipe.
See less See more
1 - 20 of 33 Posts
Cobb downpipe installation pics
See less See more
Nice sok07....Thanks. I guess what i really want to know is, does replacing the oem dp w/ a aftermarket (w/ hf cat) ones (does not matter w/c brand) can contribute to the demise of the turbo seals (w/c in part, leads to smoking turbo problems)? Hate to be doing all these and then ending up w/ busted seals.
thanks, i was just asking for a how to 2 hours ago. It seems a bit more involved than i thought it would be.

Is removing intercooler and doing all that stuff on top necessery? i will have a lift available when i'll be doing my install.
Wow just the thread I have been looking for these past few days this deserves to be stickied also this is perfect for us who do not know what to expect and do not have an access to a lift. Not so bad now that I look at it. These past months all we had were the terrible stories and mentions of the 5-6 hour install. How long should it take fairly also what dp do u recommend other than the cpe or Cobb?
i vote for sticky...awesome pictures like always sok!
Thanks for this "how-to", sok07. Seems sticky-worthy to me, and so it shall be.
great job, did an excellent job with pointing out exactly where the bolts are, because most write ups don't have their locations pointed out when all the parts are still bolted up...:D
Yeah, something as simple as circling the bolts or otherwise getting the user to focus on what's important in that picture is very cool and generally not done. Good job.
how long did you have it soaking? i'm at about 20k miles. I was thinking, taking intercooler and heatshields off, then spraying, doing an oil change or taking off the brace under the car.... should i let it soak for 20-30min?
I sprayed my O2 sensor with PB the evening before the install while the engine was still warm. I took off the TMIC and sprayed down the (5) downpipe nuts/studs and the O2 sensor (under the little hat). I resprayed again before I started removing all of the heatshields.
thanks for the write up, i'll be doing mine in a couple of weeks.
A couple of questions
did you mount the downpipe to the stock exhaust and did you need to buy another dount gasket. Did you reuse the gasket that the pipe meets the manifold.
I re-used one of the donut gaskets. There are two on the stock downpipe/midpipe/cat-back system, so you will have a spare. :D
got a quick question. yesterday i installed CS downpipe (what a pita), and i am confused with O2 wiring. The top O2 sensor wire is not really held up by anything, it's kind of leaning on the DP. How did you make it not lean on it? i'm affraid it's going to melt or burn or w/e.... The stock dp had those little springs that kept it from leaning against the dp.... or is this normal, and it won't burn?
also, when i installed my rp, my turbo was smoking. It was replaced by the dealer. There were no problems. Now i installed the dp and there is similar smoke. I mean it could be from all the crap burning up (wd40 etc), but what are the chances that this turbo will need a replacement as well?
[quote author=sleserginekolog link=topic=137517.msg2990266#msg2990266 date=1236878120]
got a quick question. yesterday i installed CS downpipe (what a pita), and i am confused with O2 wiring. The top O2 sensor wire is not really held up by anything, it's kind of leaning on the DP. How did you make it not lean on it? i'm affraid it's going to melt or burn or w/e.... The stock dp had those little springs that kept it from leaning against the dp.... or is this normal, and it won't burn?

Not sure about the turbo-smoke issue. I haven't had any problem with the smoke on my car, then again I'm running a catted downpipe and also running rotella 5w40 syn oil.

As for the O2 sensor wire. I crudely bolted/mounted one of the clips on the foam heatshield and clipped the wire to it.
wow, i didn't fugure that, definatly need to do that.

i think i may be in need of the new turbo again. it looks very similar, smoking after i idle for couple of minutes. hold on... how does the smoke look after the dp install(like the burning of the internals, and wd40)? and how long does that smoke last? i already drove 90 miles and smoke is still present...

btw, apparently when i did the install, i didn't tighten the racepipe too good... after install i was amazed with the sound, it sounded soooo sexy :lol: i was like an STI with 3inch catback. but... i heard a little bit of exhaust leak, so went back to the shop today. Tightened everything (quite a bit), and now :( i sound just like when i had just the RP :( no more STI sound. i wonder if i unbolted a bit :woohoo: , or should i just cut out one of the mufflers?
sok07 where did you get your o2 sensor tool (crow foot thing) i cant seem to find it. i have the socket o2 sensor what a piece of crap.

edit: i found it, and the sensor that i had was the wrong size (opening was too big)
Insane workup! This is why I come to this forum! I only have one question:

What are the torque down ratings for all the bolts (in either lb-ft, inch-ft, newton-metres)?
I had a TurboXS downpipe installed by a shop locally and they stated the O2 sensor was either over tightened or cross threaded by the factory which then meant upon removal ruined the sensor needing to be replaced. This sensor apparently costs 400+. Anyone with any experience on this?
1 - 20 of 33 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.