Rattle after Cat protector installation

A 500 ton hydraulic press and matching obverse and reverse dies for each panel that makes up a cat shield cannot be afforded by any organization but a high volume manufacturer like Toyota or Tesla.

Hydro-forming would be less expensive but more time consuming and more labor intensive.

Making one at a time by hammering and an English wheel would cost too much in labor.

I really don't like the Miller Cat method of sending the shield flat and having the installer bend it along the line of some weak tabs.

I prefer the least expensive method of making linear bends with a sheet metal bending brake to achieve stiffness and clearance in the matter that I have done mine by bending it over a 2x4. It's really cheap, and it works.

If the shields were pre-bent, the only extra cost would be of a few quick bends with the brake and a thicker box.

 

Yes
The use of a brake would do what I suggested, wouldn’t look as nice but who sees it anyway?

 

In February 2022 I purchased and installed what I believe was Rev 2 of the Stainless Steel MILLERCAT 2004-2009 Prius Gen 2 Cat Shield Complete Package with the MILLERCAT Custom Screws and two new MILLERCAT hangers plus the Deadbolt. Looking at the MILLERCAT web site now in October 2022, there is a new version that appears to add quite a bit of bottom clearance which may clear up any problems with the cat contacting the shield. My version was still very much a flat plate.

The install on my 2006 Gen 2 with its original cat went very smoothly thanks to the excellent instructions and quality hardware supplied with the kit, along with posts on Priuschat and YouTube videos. I purchased an inexpensive 16" Rivet Nut Tool for the rivet nuts which worked just fine. I was able to get enough clearance to work under the car with my Rhino ramps front and jack stands rear. Had a couple of studs break off which I fixed with rivet nuts from my nut tool kit. All in all, the install process was excellent. Test rides after install evidenced no noise or rattling.

Shortly after I took off for a 4000 mile road trip which is why I was so anxious to get a good cat shield on. The news and videos of cat thieves on Gen 2s absolutely scared the heck out of me. The last thing I wanted to wake up to is a cat-less Prius 2000 miles from home.

About 1000 miles into the trip I started to hear a clunking noise during acceleration and a creaking/groaning noise. When I got to my destination I borrowed jack stands so I could crawl under and figure out what was going on. Finally I noticed the lower engine mount's resonance damper had broken off - my plea for help is on this thread: Does this look familiar? (please help) | PriusChat
Good folks on Priuschat helped me diagnose and let me know I could fix it when I got back home.

When I arrived home I replaced the lower engine mount which took care of the clunking noise. But the creaking/groaning noise was still there! It occurred regularly but not correlated to anything I could figure out - it would happen on acceleration, deacceleration, cornering, braking, anytime, even when the engine was off and rolling - I just could not trace it to one action. It was driving me crazy. I even changed my transaxle fluid to see if the old fluid could tell me anything about the tranny (which it didn't). Yes, I suspected the cat shield but the noise just wasn't a rattle or a buzzing like you would get with an exhaust pipe hitting metal. And I had put on the new hangers as MILLERCAT recommended.

I finally spent some screen time searching the net for anyone with a similar problem, and specifically tied to a cat shield install. I found a reviewer of the MILLERCAT system who had a few comments about how to stop the cat shield rattle and he suggested "replace the 2 hangers but hook it (HOLE to center of the hanger) so it will take the CAT up so there is 1.5" of clearance". A couple of days ago I went out and slipped the hangers out of the exhaust assembly hanger rod and poked that rod through the center of the hanger on both sides. I've had the car out for about 25 miles now and guess what - no more creaking! I guess the cat was close enough to just touch and make the creaky sounds without rubbing enough to rattle. Anyway sorry for the long post but if it helps one person from going through the worry I've been having it will be good!

 

There is one in a 3-dimensional shape from MILLERCAT 2004-2009 Prius Gen 2 V2 Cat Shield

 

Hey everyone,

I thought this information might be useful for you.

I arrived in the US from Ukraine nine months ago due to the war. After purchasing a Prius 2015 Gen 3 Series Two, thieves stole the catalytic converter. I found an Exhaust Intermediate Pipe 17410-37300 OEM for $1300 and a 89465-76010 Oxygen Sensor for $117.22 from a dealership near Laguna Beach (Capistrano Valley Toyota). Additionally, I ordered a Millercat Shield V2 Gen 3 for $260. I found a mechanic who installed it for $220.

However, I noticed a rattling sound after the cat protector installation. If you're experiencing this issue, I suggest getting under the car and loosening the cat shield to check for scratches. My mechanic forgot to turn a particular piece, causing the problem:




So, that was the issue. After I turned that piece to the side, everything sounds perfect!
I hope this helps if you're experiencing a similar problem, and I hope your engine and catalytic converter are okay.