Rattling Cat??

1990 740GL is rattling underneath at various RPMs. I ducked under for a
look-and-listen, and it seems the cat converter is the source of the
rattle. It doesn't seem loose, so I assume something inside is broken
loose.

It's an aftermarket cat, installed only about 2 years ago (20K miles).
Seems too soon for it to break, unless I got a very low-quality part.
Any way to fix the rattle without buying a new cat?

 

If in the USA/Canada then buy a new cat, the old one has gone silly and
loosened it's internals which will muck up your emissions. If in UK replace
the cat with a straight pipe or ordinary front silencer box. Make sure it is
not the heat guards working loose between exhaust and body.

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

I'm in the US. Heat shields were not rattling, so I guess I'll get a
new cat. Thanks Peter.

 

not PC, but whatabout pounding a pipe through it? (might even reclaim
the Pt scraps...) its a no-solution problem, talk to a friend.


: 1990 740GL is rattling underneath at various RPMs. I ducked under for a
: look-and-listen, and it seems the cat converter is the source of the
: rattle. It doesn't seem loose, so I assume something inside is broken
: loose.

: It's an aftermarket cat, installed only about 2 years ago (20K miles).
: Seems too soon for it to break, unless I got a very low-quality part.
: Any way to fix the rattle without buying a new cat?

--

 

I am a tight wad so when I get a rattle in an exhaust or cat I drill a
small hole near where the rattle is and pump silastic in till the rattle
stops .With heat the silastic hardens but doesn't burn and has worked
for me many times .If it goes another few years its fine by me .

 

This happened to me 3 times on my 1982 VW Rabbit. It turns out that, because
I was using cheap gas, the engine was backfiring. This caused the "matrix"
in the cat to come apart. I had Midas replace the cat. twice, not telling
them that the engine was backfiring. The last time it happened, I took off
the cat and busted up all the pieces in the cat with a broom handle, making
the pieces small enough to empty out of the cat. If you don't take the
pieces out, one of them will eventually block the cat's outlet and your
engine will stop because of the backed up exhaust gases!!!

 

I did that once, the car still passed the emissions check easily and in
fact was cleaner than the non-Volvo I was driving at the time.