Hey everyone,

So ever since I bought the car I noticed a loud rattle sound when the car is in motion. I cant seem to replicate it when revving the car when parked. Only when cruising around town. I put the car on a lift and did the test with a rubber hammer and confirmed that 2 of the cats are going bad (slight rattle when tapped). I just making sure that before i go and replace the 2 cats (passenger side primary and secondary) that its not something else that could be making the noise. I have checked the bolts on the heat shield for the exhaust and all bolts were tight nothing loose. I also checked the flex discs and center support bushing for the driveshaft and all checked out good.

So before i go and have them replaced do you think its possible that something else could be making the loud rattling noise? I thought cats since i confirmed 2 are starting to fail but I'm starting to think the rattle is way louder than what those cats made when smacked with a hammer. Could it be the rear brakes chattering? I do plan to replace the rear wheel bearings since I'm also dealing with a loud howling noise from the rear when I'm driving 30 mph or faster. Its the worst at 50 mph and seems to quiet down a little bit at 60 mph and up.

My plan of attack is as follows:

Replace the passenger side cats (Possibly do a muffler delete since I'm there anyways? Not sure how bad the drone will be in the cabin.)
Replace the rear wheel bearings
Flush the rear diff and refill with fresh fluid (When i checked the fluid before it was very black and pretty old)


I know a lot of people say howling noises can happen due to the ABC system. I have already converted the car to strutmasters and looped the tandem pump back to reservoir. I have not yet removed the old accumulators or valve blocks tho. Could they still be causing the howling noise even tho they are not being fed by the system anymore?

Any help on this is much appreciated. I figure at least if i get this all done i know it wont have to be addressed anymore and hopefully the noises are gone but who knows. Oh yeah the car has about 167k miles so i figure its about the time in its life for all these things to fail. Also to add onto this I have directional Z rated tires on the car all around (previous owner installed them before sale) and i have heard that they can make a lot of noise but the howling noise is so loud you cant hear anyone talking if they are in the back of the car. Its super annoying!!


- Logan

 

So update time....

I called the local exhaust shop and they quoted me 520 for new primary and secondary cat for the passenger side. Walker brand and not high flow. I'm thinking that's a bit much to pay for aftermarket non high flow cats. My new plan is to go by there and see how much to just replace the passenger primary and delete both the secondary cats and keep the stock mufflers in place.

Im not expecting a huge increase in noise since I'm gonna keep the mufflers but i will definitely save some money by deleting the secondaries instead of overpaying for a replacement. I live in CA so i know there is risk of not passing Smog inspection but really i havn't seen a tech get under the car to count the cats and they don't do a sniffer test on 00 and up here. Should be all good and hopefully i save a bit of money. Will report back after.

Sadly.... I'm not able to make the time this weekend for the rear diff, front ball joint, and wheel bearing replacement. That gonna have to wait till next weekend.

 

Another update.... Replaced the passenger rear cat and the rattle is still there. Yesterday i went out to the car and started to shake the mufflers with my hand and found that the drivers side muffler has a piece of debris in it and it causing a loud rattle. Most likely a piece of the cat that probably made its way into the muffler or the baffle inside the muffler has started to come apart as well. Wouldn't be surprised since this car is 17 years old. Gonna take the car today to have the mufflers deleted and hopefully that's the trick to no more rattles on this car. Wish me luck haha.

I will be sure to report back with results. I did finally get around to replacing the mirror gaskets and found a nice little spider that was taking residence in my drivers side mirror housing. Not having the right length torx made this job nearly impossible to do but it was eventually taken care of.

 

 

Yeah, the car is a bit too quiet. I was mainly worried about drone in the cabin... I was reading that the secondary cats are basically resonators. Is that true?

 

 

Deleted the mufflers yesterday and the sound is really good considering. There is a bit of drone in the cabin but still hard to gauge how much because my rear wheel bearings are screaming loud haha. Cant wait to get those sorted. Sadly tho the rattle is still there so thinking its the front primary cats or has to be something with the rear wheel bearings or brakes. When it rains i notice the rattle is not there or im just not hearing it anymore. Hard to say but if the rain makes it go away then im thinking it could be brake chatter. Weird thing is when i do hear the rattle noise and i hit the brakes the noise still continues so its hard to believe its the brakes.

Driving me crazy!!