Is there a specific sound a mustang will make when the cats are bad?? I have this LOUD ANNOYING rattling sound coming from my exhaust, mostly on deceleration
Do you still have the stock H-pipe or an aftermarket version? Reason I ask is because I thought the factory cats had heat shields on top of them, which might have come loose and could be rattling. IIRC my BBK catted X pipe doesn't have heat shields on the cats. But it is possible for the block of catalyst to get loose and rattle inside the casing. Been there, had that, very annoying (and embarassing) sound. Best thing would be to get under the car and bang on the bottom of the cats with the side of your fist. If the catalyst is loose, you will hear it bouncing around. Check the heat shields (usually welded solid to the cat. body) to see if any are loose. If all checks out, check the entire exhaust system for signs of scuff marks which may indicate that something is rubbing.
Yeah that happened to me. Really annoying rattling sound and eventually it got logged into the pipe and blocked the flow which was scary, it made the car sound like a WRX. It took a couple weeks before it logged itself. AT that point I pulled the H-pipe and saw it loose in there. I proceeded to "remove" both pre-cat cores with a long crowbar and all was well after that.
I don't know about the rattle, but when my cats were going out, I noticed an extreme amount of back pressure, so much that getting up to higher rpms took some serious pedal.. Got an h-pipe/no cats = no back pressure...
Could be a heat shield too. BTW, I have been told by 2 mechanics that cats don't go bad unless the tune (stock or other) is bad and throws them off for too long. - Just another reason to make sure you car is running well, especially after you replace with new cats.
Do you still have the stock H-pipe or an aftermarket version? Reason I ask is because I thought the factory cats had heat shields on top of them, which might have come loose and could be rattling. IIRC my BBK catted X pipe doesn't have heat shields on the cats. But it is possible for the block of catalyst to get loose and rattle inside the casing. Been there, had that, very annoying (and embarassing) sound. Best thing would be to get under the car and bang on the bottom of the cats with the side of your fist. If the catalyst is loose, you will hear it bouncing around. Check the heat shields (usually welded solid to the cat. body) to see if any are loose. If all checks out, check the entire exhaust system for signs of scuff marks which may indicate that something is rubbing.
+1 to heat shield.Did mine yesterday , weld was loose , had to bend it up(temp. fix ) and talking about embarassing sound , when I "fix'" it I was like driwing new car
glad we dont gotta run cats in michigan but how does your car act when driving does it seem restricted? the hollowing out trick works well if they are pluged up just remember bang from the oposite direction of exhaust flow you will see tons of black pellets falling out....that means its working
If you have a vacuum gauge, hook it to manifold vac and bring the RPM's up to 2.5K and hold it rock steady. If the vacuum reading starts to drop after 30 seconds to a minute, there's an exhaust restriction. And the cats are the first place I check for restrictions.