Exhaust smell inside cabin and rattle when accelerating

JUNIEYANEZ

MEMBER
2005 SUBARU OUTBACK
2.5L
6 CYL
4WD
AUTOMATIC
209,000 MILES

Recently my car started overheating due to a leak in my heater hose. I got it replaced a few days ago and the problem was solved! Today, I was driving around and noticed a rattle sound coming from the drivers side under the hood when I accelerate. The car still accelerates but is slightly less powerful and exhaust fumes quickly built up in my car. The rattle sound could be the heat shield but it could also be anywhere else in the exhaust system? Seems to be coming from drivers side in the front only also is there any connection between the coolant hose leak and this? Or was this just two unfortunate unrelated car problems

7 Replies

JACOBANDNICKOLAS

MECHANIC
108,171 POSTS

Hi.

There is a chance the catalytic converter has come apart internally. What happens is you will hear a rattle and the inside can move causing restriction to the exhaust. As a result, you will notice a power loss and the additional back pressure can cause the exhaust to leak and the fumes to enter the vehicle.

What I suggest is this. Take a rubber mallet and tap pm the exhaust to see if you can locate the noise. A heat shield can rattle, but won't cause a power loss or the smell.

Try that and let me know what you find.

Take care,
Joe

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Friday, November 15th, 2019 AT 10:17 PM

JUNIEYANEZ

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Is there any chance it could be something besides the catalytic converter like a simple leak? Or O2 sensor? I hear those have the same symptoms? Taking it to a mechanic soon but will try that when I get home! Update soon

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Saturday, November 16th, 2019 AT 1:02 PM

JACOBANDNICKOLAS

MECHANIC
108,171 POSTS

I have to be honest. It could be other things as well. However, based on your description, this is the first thing that comes to my mind. Were you able to check it? As far as an O2 sensor, they wouldn't cause a noise. There could be an exhaust leak, but that would either be a louder engine sound or if it is a small leak, it could sound like a ticking.

Let me know.

Joe

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Saturday, November 16th, 2019 AT 6:20 PM

JUNIEYANEZ

MEMBER
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Hopefully the last time I ask on this thread, but I had my CEL ran and the only code that came up was a code for my Air flow sensor. I was told my air filter could need changing as-well. The rattling noise seems to have disappeared? But I haven’t driven on the highway so maybe it only appears after my car has been driven for longer or at faster speeds. Could that possibly mean anything for this problem or is this entirely separate?

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Sunday, November 17th, 2019 AT 8:09 AM

JACOBANDNICKOLAS

MECHANIC
108,171 POSTS

Hi:

The mass air flow sensor measures the rate of air entering a fuel-injected engine. The air mass information is necessary for the engine control unit to provide the correct amount of fuel to the engine. The sensor could be bad, a plugged air filter could cause it, an engine vacuum leak can be an issue, and so on.

By any chance, do you know what specific code was found? That would help me.

As far as the noise, if it's gone, great. However, if it is in the catalytic converter, it may come back. Lets hope not. LOL

Also, feel free to ask as many questions as you have. The only thing is if the topic changes. Then we like to start a new thread.

Let me know.

Joe