I took a peek at the motor mounts today to try and address some annoying intermittent rattling from the exhaust. Unfortunately I'm not quite sure the if it's the motor mounts or something else .

I haven't yet taken a video of the rattling, I let the car run on stands for a bit today but it wouldn't rattle for me. I was however able to video the motor in and engine bay in slow-mo and inspect the mounts. I've attached a few pics of the mounts and a link to the video but when it was idling I didn't see any wild vibration and while the car was off and I felt and tried to image the mounts but couldn't see any damage.

From what I can tell the exhaust and hangars look alright although I'm nearly certain that's the source of the rattling, it seems to happen when slowing down and stopping after the car has warmed up and will very slightly drop in idle. Not a full on shudder and the car doesn't seem to have compression issues from what I've tested and the power it provides just the slight drop in RPM seems to propagate through the exhaust and make a nice loud rattle on occasion.

I'd hate to pull out and cut open good mounts and have to wait 5-6 days for urethane to cure for nothing.

Pictures:

 

Perhaps a video of the exhaust acting up would help...

I should mention I think the exhaust is hanging slightly lower than it used to but it is aftermarket so it could potentially be due to being a slightly larger pipe with different hangers.

 

Hmmm. That seems like too much movement. Usually these engines sit pretty still.
At the same time, the mounts don't look too bad. Has this engine or transmission ever been removed? If so, perhaps the power plant frame hasn't been properly replaced.

What exactly do you mean by 'exhaust sits lower'? Lower at the tips or under the car? Because there's a bunch of hangers along the way that should place it properly.

Also the rattle could be loose cat heatshields. The rpm drop and rattle should correspond with the AC compressor kicking in, which isn't unusual. Usually its a feeling not a sound, but if there's a sound the best we can do is narrow it down to a specific spot on the car.

 

Did you cheat and read my post history 😂.

I did swap my clutch a couple months ago but the noise and vibration was there long beforehand and I was pretty careful to line the nuts up exactly where the previous markings were on the PPF and then torqued them. I suppose I can take another look to be sure nothing is way off.

 

The AC compressor feeling is something I'm not unused to, surprisingly this isn't even as violent as that. Lower under the car meaning to the point I can't install both crossbraces but that could be more to do with worn rubber hangers or the non stock exhaust. By heatshield do you mean the metal one that protects the tank?

I dont think it's the cat, I have a fairly new high-flow one in and when I had the exhaust off for the clutch I gave it a good shake and heard nothing loose in the midpipe.

I'll try and capture a video later, maybe running the AC will help prompt it to make its noise. Almost seems like a resonant frequency that triggers it hence it being so intermittent.

Also it's hard to say based on just reading the TSB but I always have felt like the car, while pretty peppy has a slight lag when hitting the gas in 3rd at like 3k rpm. I seem to remember that being an indication of worn mounts.

 

Hmmm. The mounts are probably not innocent in this, but it is weird that you can't put the crossbraces back. Perhaps there are multiple things going on here.

The heatshield I was referring to is right above (and for a stock cat, below) the cat. With time and weather the brackets rust away and the whole thing flaps in the wind or rests on the cat and rattles.

 

Not a bad guess, I'll check if anything is up with it when I get under there again later today.