rpfn140378

Hi all

Once again I need your help.
The middle part of my civic's exhaust has a hair thin crack and it is starting to make some noise. The thing is, there is something connected with a wire to the exhaust and I don't know the name of it and what it does, please see the picture, it has a red circle around it. I would like to change the exhaust myself as I did another day with the rear box of the exhaust, but I would like to know what kind of care I should take with this thing while replacing the exhaust.
Any help will be appreciated.

94EG8

That's the secondary oxygen (O2) sensor. Sometimes they're difficult to impossible to remove depending on how bad they're seized in the catalytic converter. Pull the rubber grommet out of the floor to access the plug.

Hondahg

If you're asking what that is...maybe you should put the tools down because something bad is bound to happen.

B serious

iTrader: (1)

It's a secondary O2 sensor. Why do you need to take it out?

If you need to take the cat down, the easier thing to do is pull the grommet out of the floor and unplug it. Then you can remove the cat and O2 as an assembly.

Be careful with the cat and sensor. I always use a torch to heat the bolts before removal.

Easiest way to remove the 3 bolts holding the cat to the exhaust is to first take off the 2 spring bolts from the header. Then unplug the O2 sensor as I described. Then slip the exhaust off the hanger right by the cat. When it's at a downward angle after removing the hanger, it's easier to put an impact in there.

If you're doing this by hand...then...that sucks. But it's do-able.

crazyhouse2011

Secondary oxygen sensor.

It seems like a good time to replace the whole setup. Magnaflow high flow cat, new secondary o2 sensor, and a magnaflow catback, probably will run you around 600 or so for parts, and another 150 or so to have it thrown in. Good idea.

rpfn140378

Thanks you guys for your prompt replies.
The reason I think I need to take the secondary 02 sensor out is to replace the middle box of the exhaust because it is the place where I have a crack. To be honest, I took this picture when I replaced the rear exhaust but I didn't looked properly how many parts this middle section of the exhaust is made of. I know there are one box and the cat. I thought they are all together in one piece, replacing the middle box, I thought I need to replace the cat as well. As I said I haven't lifted the car yet to have a proper look.
Does the secondary 02 sensor come together when you buy a new cat or not really?

94EG8

The cat bolts to the intermediate pipe (the middle pipe you speak of) if it's the middle part that's cracked there's no need to replace the cat.

No it doesn't.

rpfn140378

Thanks for your reply. I don't think I will have time tomorrow to lift up the car and have a proper look. I will try to take a closer pic of the place where the crack showed up without lifting the car up and show you. I was really convinced that the cat and the box were all connected by the pipe that connects again to the rear box. So possibly it will be easier to replace the box as I can see on the picture the 02 sensor is connected to the cat.

Effin-Jay

Im sure there was a time when all of u didn't know what an O2 sensor was either so kinda go easy on the kid ****

Hondahg

I was just razzing the guy. Sheesh. Purely joking!

There is a special socket for it. It has a 'slice' down the length of it so the wire goes through. If you use an open end wrench you will round the sensor. I would suggest you buy one if you attempt this. Its going to be frozen in there so also hit it with some pb blaster.

As for the crack...I "fixed" my exhaust manifold crack. I bought a plastic jar of a metal goop from pep boys. It is separated in the jar and you mix it up and spread it on. It says it can withstand temps of 1400 if memory serves. Definitely not a permanent fix but it beat the alternative. You could try that for the time being. It dries very hard.

rpfn140378

Hi again
Today I managed time to lift up the car and I took another picture. It is marked in red where the crack is. I had the car in the garage twice to weld it up and ends up cracking somewhere around where it was welded last time. So I don't want to spend more money welding up that box. While the car was up, I had a proper look at the exhaust pipe that comes from that box to the cat, you guys are right, there are 3 bolts but because they are kind of hidden within the cat's shield I never noticed these 3 bolts. They are pretty rusty and also are the bolts of the shield, so good luck on me to remove them.
Probably one day before I change the box I will put a bit of WD-40 to help. I wonder if there is any gasket between the cat and the pipe where the bolts are?
Thanks for your help.

94EG8

That box is the resonator. Yes there is a gasket, actually there's one at each end of the pipe. The one that goes at the cat end purchase at your local Honda dealer, it should be part number 18393-SH3-S00 and fits in a groove in the flange of the cat. Generally a parts store will try to sell you a big flat gasket that doesn't seal well. The doughnut gasket for the other end of the pipe can be purchased at a parts store though.

rpfn140378

If the doughnut gasket you are talking about is the same as the one I have on the pic so I have 2 spare ones at home. As I have 2 civics I always keep some bits and pieces spare at home. The other basket that goes on the cat I don't have it. I will ask in my local parts place if they sale it otherwise I will order it from Honda. And I will prepare my blow torch for the bolts. They are really rusty.

94EG8

Yes that's the gasket.

rpfn140378

Just checked my local parts website and the only one they have is called "down pipe gasket" I will called them to find out if it is the same size as the one that goes on the cat.