I have a 98 Civic LX that I picked up used with about 50k on it. Since picking it up, it has been having a strange noise at about 3k on up and in any gear.

It has been stumping me on where it is coming from because I cannot duplicate it while not moving. But the problem is definately not driveline related.

The noise sounds something like an air pump. It's sort of deep sounding and increases with engine rpm. The sound is not there when I first start the car, but as it warms up it can definately be heard.

What I am thinking is that it is the catalytic converter or something in the exhaust.

Any ideas or recommendations for me to check?

 

LX huh? Is the catalytic converter part of the exhaust manifold? It definitely could be an exhaust leak, but I find most noises in my car are just loose things rattling.

 

Yeh, LX. I have never seen this type of exhaust setup. The Cat is part of the exhaust manifold. It does sort of sound like an exhaust leak though, but it is hard to tell. There was a header back put on a little while ago, just some Midas exhaust.

Other than this noise, the car is in great shape.

 

Sounds sort of like an air pump. One of those little ones that you can buy that plugs into your cigarette lighter.

 

check around where the primary o2 sensor goes into the header/cat. That area is prone to cracking.

honda issued an extended warrenty on this. If it is indeed cracked, search the forum for a thread I posted a month or two back that talkes about the warrenty... maybe I'll link it if I can find it real quick....

 

aqui

https://www.honda-acura.net/forums/s...ifold+warrenty

 

Wow, thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
This really has had me stumped and looks like this might be my problem. I will look at it pretty thoroughly in the morning, but I am real sure that this is the problem.

 

Ok. I just checked things out. Pulled the heat shield off (left the O2 sensor in place) and did a visual. I cannot tell if it is cracked or not. The manifold doesn't look like it has ever been replaced, but it is also not too bad. A little rusty.

Is there any other way to check this out?

 

eh, you still have low milage :dunno:

I started noticing around 60-70k on the o.

these were small cracks, definatly nothing large. hairline, almost.... but then again, you have till 150k

 

So do you don't think this is where my noise is coming from?