Exhaust leak when cold

[2010Civic]

Recently got my wife a 2010 Civic LX with 118k miles on it. I've noticed that when you cold start it the engine sounds louder than normal for the first mile or so then is quiet for the rest of the day until you start it from cold again.

My best guess is it sounds like an exhaust leak. The sound is coming from the front and not in the rear. I'm thinking that maybe the donut gasket between the cat and the a-pipe is bad but when warmed up seals again. Has anyone ever experienced this? Here is a picture of that connection. A little rusty but nothing looks terrible.

 

[B1974]

It could be that donut gasket, but could also be a cracked exhaust manifold or it could be leaking at the head to manifold joint.

Also it could be a loose spark plug, check those first.

You'll need to get under the hood to listen for where the leak is coming from to tell for sure.

 

[Graham Piccinini]

Possible. Try a replacement donut, those seem to be in $5-$20 range from parts stores.
Or a redneck "fix" would be to coat the old donut in red high temp RTV and stick it back in. Not pretty, but it works if you let it dry for a few hours before starting.

 

[GSCJR]

It could be that donut gasket, but could also be a cracked exhaust manifold or it could be leaking at the head to manifold joint.

Also it could be a loose spark plug, check those first.

You'll need to get under the hood to listen for where the leak is coming from to tell for sure.

This is solid advice right here . Investigate first, disassemble second.

 

[eljefino]

Those donut gaskets are a wear item and the springs in the bolts take up the wear. If you switch it for "no reason" it's almost like preventative maintenance-- the new one will be meatier.

 

[jhellwig]

Manifolds like to leak when cold on some engines. Some don’t used exhaust gaskets so after the years stuff warps and leaks a little when cold.

 

[Chris142]

Usually the leak is at the head or a cracked manifold.

 

[B1974]

The 1.8L R18 engine has a sort of a internal exhaust collector in the head that bolts up to a catalytic converter down pipe with four bolts/studs. I would check to see if any of these are loose.

 

[JamesBond]

Have you started the car from cold and just felt around the joints with your hand before it gets hot? Have you started the car and listened outside of the car?

The reason I ask is because I have an older civic with cheap replacement motor mounts and when I start the car when cold from inside the cabin it is very loud but outside it sounds normal. The hard engine mounts cause a booming resonance inside the vehicle which improves once the engine and mount warms up.

 

[2010Civic]

Have you started the car from cold and just felt around the joints with your hand before it gets hot? Have you started the car and listened outside of the car?

The reason I ask is because I have an older civic with cheap replacement motor mounts and when I start the car when cold from inside the cabin it is very loud but outside it sounds normal. The hard engine mounts cause a booming resonance inside the vehicle which improves once the engine and mount warms up.

Yeah, I have put my hand near the joint and didn't feel any air.

I was also thinking it could be engine mounts but I haven't noticed any extra vibrations that usually come from bad mounts. Was there vibrations in the cabin besides the booming resonance?

Comparing the engine mounts to my other 2010 Civic they look fine. Not collapsed or usual looking. I may loosen all the mounts, shake the engine around and retighten. Sometimes they get weird pressure on them.

We bought the car with damage (see pic) but I wouldn't think that damage would disturb the engine mounts.




After:

 

[D60]

Grab some fuel line, stick one end in your ear and the other near any suspected leak points. You WILL hear it when you find it.

Works great, basically free

 

[JamesBond]

My replacement mount makes the engine feel more “buzzy?” especially when cold and at idle. Maybe one of your mounts have already been replaced with an aftermarket mount.