Announcement

Collapse
No announcement yet.

Loud sound from cat but no exhaust leak?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Loud sound from cat but no exhaust leak?

    Hi everyone,

    I picked up an 89 325i last summer in pretty rough shape and have slowly been restoring it to the best of my ability. First time owning a BMW.

    When I picked it up, it did not have an exhaust past the cat flange as it was rotted off. I built my own 2" catback with a flow master super 50 series at the back. The exhaust sounds good, maybe a bit loud if anything but it sounds like it has a nasty exhaust leak between approx. 1500 and 3500 rpm. Sound like it is coming from the cat area but I cannot find any leaks. I pressurized the system with a shop vac and sprayed soapy water everywhere and do not see any bubbling. Exhaust manifold has new seals and it is in good shape, as is the piping from the exhaust manifold to the cat but if I am underneath the car and someone revs it, I can basically hear the sound of the engine from the pipe which seems strange.

    Is it possible that a cat would rust from the inside causing the metal to thin out and let more sound escape while not actually having an exhaust leak? Almost like having a cat made from tin foil?

    I know these cars make quite a lot of engine noise but it doesn't seem like it would have come from the factory with an exhaust sound like this and I just find the noise irritating when I get on the gas. If I coast in the rpm range, it goes away but any load on the engine and it comes back. Its not as loud in the engine bay so I am quite sure its not coming from the engine. I have checked and rechecked my rocker adjustment too just to confirm thats not it.

    I've read a lot on this forum over the past year about everything to do with these cars and it seems like there is a lot of good info on here!

    Thanks

    #2
    something broke off inside

    replace it
    Originally posted by wholepailofwater
    Q
    :devil:


    WTB: Dove Grey e36 Front Door Panels (2 door)

    Comment

    Working...
    X