[cmitchell17]

I got the dealer to do the epoxy fix to my NPP at about 30k, I'm at 65k now and things are rattling like crazy. I tried to clean and epoxy the valves today, which I think I did improve the rattle or either I fixed one rattle and another still remains.


I used my scanner to step up through the rpms and see if I could make it rattle, it kind of worked at about 1500rpms, but it sounds like its coming from inside the suitcase muffler.


I also had a rattle up front near the cats, I saw a TSB about the bracket that holds the cat needing a locknut put on it. I ended up taking off the secondary cat heat shield and using a impact gun to re-tighten the bracket that holds the primary cats on. Thankfully that fixed that rattle, but the rattle that still remains I feel like might be from the AFM valves?


It appears the "actuator" PN: 22839592, is the same for the AFM valves and NPP. So I would think the AFM valves would have the exact same rattle problem.


Has anyone tried taking the actuators off? It would be a lot easier to epoxy or weld on or try to fix if it was out of the car. I could also take the whole actuator out and disable AFM, im not sure how I would plug it? I guess the manual cars have some piece that blocks off the actuator hole? or either the exhaust is a different part number for m6 cars?

[Mark114]

You can unbolt the actuator (black plastic) from the AFM valve in the exhaust but the actual mechanical valve is built into the exhaust. If you remove the actuator it may help you check the valve to see if this is the source of your rattle. The M6 cars have a different exhaust without the AFM valve.

[mdhopt36]

Interesting.

The annoying thing I notice, is from going back and forth from 4 cylinder mode, the dayam thing clacks open and shut. makes for sounding like a POS.

[cmitchell17]

Originally Posted by Mark114

You can unbolt the actuator (black plastic) from the AFM valve in the exhaust but the actual mechanical valve is built into the exhaust. If you remove the actuator it may help you check the valve to see if this is the source of your rattle. The M6 cars have a different exhaust without the AFM valve.

Thanks! and yeah I was talking about trying to remove the actual butterfly valve and it looks like its welded in.

On a side note, I'm assuming the AFM valves literally just close and block off the exhaust, and this somehow quiets the exhaust down enough to where you don't hear 4 cylinder sounds?

I used the scanner to force the AFM valves to close and then floored it and you can definitely feel it lose power and throws off the WOT shifting. After you do it a few times the programming cuts off the function.

Also I've heard people can tell its vibrating by taking a long screwdriver and touching it to the butterfly valve while its running? I tried this and didn't notice any vibration, next im going to get a rubber mallet and get under there and start hitting things to see if I can hear anything lose.

[mdhopt36]

" I was talking about trying to remove the actual butterfly valve...."

Exactly what I was thinking, at least partially.

If you have a die grinder, it could be un-welded temporarily...??

[ctrlz]

Originally Posted by Mark114

You can unbolt the actuator (black plastic) from the AFM valve in the exhaust but the actual mechanical valve is built into the exhaust. If you remove the actuator it may help you check the valve to see if this is the source of your rattle. The M6 cars have a different exhaust without the AFM valve.

from this picture it looks like the device has a solenoid with a plunger that probably connects to a lever attached to the valve. there may be some intermediate gearing. it would be nice to have a bad unit to cut open to see what is inside.
I suspect you could take a dremel and make a parallel cut next to the plunger to sever the lever mechanism. That might allow you to permanently fix the valve open or closed. The plunger would still be able to move but it would not be attached to anything.
See if the black plastic case has the plastic type stamped (it should). If it is ABS, you could probably cut the whole thing open with a dremel and glue it back together once you modify it.

[cmitchell17]

Originally Posted by ctrlz

from this picture it looks like the device has a solenoid with a plunger that probably connects to a lever attached to the valve. there may be some intermediate gearing. it would be nice to have a bad unit to cut open to see what is inside.
I suspect you could take a dremel and make a parallel cut next to the plunger to sever the lever mechanism. That might allow you to permanently fix the valve open or closed. The plunger would still be able to move but it would not be attached to anything.
See if the black plastic case has the plastic type stamped (it should). If it is ABS, you could probably cut the whole thing open with a dremel and glue it back together once you modify it.

I don't believe the rattle is coming from within the plastic, I think the rattle is coming from the same "ceramic pin" that I think the butterfly valve pivots on. This is the same ceramic pin that's referenced in the TSB for the NPP rattle.


I crawled under mine and took off the plastic actuator and hit it a few times with a rubber mallet, and I'm a little more certain the rattle is in the butterfly valve.


It still means that all of us with this problem basically have a useless $1000 dollar NPP option, since the only proper fix would be to buy a overpriced $2400 catback aftermarket exhaust, or buy a new NPP exhaust that supposedly still rattles.

Only other option is cut and weld, which would require a welder and skills enough to get it welded back right, which is complicated by the fact its factory welded very close.

So another idea I had was to drill out the whole ceramic pin? It really sucks doing things without a lift under the car, but maybe there is enough room without having to take the exhaust out (maybe its not to hard to take the whole exhaust out??) to drill from where the dimple is and maybe you could crack the ceramic pin where it would fall out, then maybe replace the whole with a bronze pin? or maybe a screw? I would think the whole valve would maybe be strong enough to stay in without the ceramic pin? If its rattling that kind of a sign it dosent even have any load on it?

[ctrlz]

I was suggesting getting into the black plastic housing and severing the link between the solenoid and the valve. Then the solenoid could still move and the car would not know what's up (I do not know what kind of fault detection may exist for this, maybe none). You could then immobilize the portion of the link which actually controls the valve, probably to keep it always open.
If you got that housing open you would have a better idea of your options for immobilizing the valve. A few shots of silicone might hold things in place for good.

[DC5]

I would remove (i.e., cut) the factory exhaust from the axle back to allow myself the opportunity to inspect it on a work bench or other flat surface. If you are unable to diagnose and/or repair the cause of the rattle, you could then simply order and install the aftermarket axle-back exhaust system of your preference and be done with it.

[ScatPack]

I would get an aftermarket exhaust and call it a day. Plenty offer the dual mode option as well. And you will be losing some big weight with that suitcase gone.

[cmitchell17]

Thanks guys for the input. I have HP tuners and can tune out the valve so that's not a problem, but with all do respect I feel like spending $2500 on some steel is just way too overpriced, especially with zero power gain and the same sound quality with potential droning. I would then be worried of someone hitting and totaling my car and having to fight the insurance company for me to be able to take it off or replace it back with the stock exhaust.

It appears there are joints about as far back as the fuel tank is, can I unbolt these and take it all out? From the YouTube videos and other information from searching it appears taking it out without a lift is a real pita and you have to pry on it to get it out. I know if I have to take out it up further at the cats that seems like it would be a real pita and having to remove the O2 sensors as well and fishing and wiggling it through.

[ctrlz]

Originally Posted by cmitchell17

seems like it would be a real pita... as well and fishing and wiggling it through.

You're not doing exhaust work right unless you're lying on your back with rust raining into your eyes and mouth.

[cmitchell17]

Originally Posted by ctrlz

You're not doing exhaust work right unless you're lying on your back with rust raining into your eyes and mouth.

Haha that's true I should just let a shop do it since I'm away from home and don't have a good place and the tools to do it right, but I hate letting someone else work on my car.

I'm thinking I'll go cut the exhaust then take the whole back half off the car so I can get to it and try the epoxy fix, then use butt clamps to join it back up when I put it back on? I know you can get down on the clamps pretty good and from my experience with them they clamp even and strong. I just don't remember a hanger being near there so I would worry about it bending and coming lose over time? If course it would probably be temporary until I could make a trip back home and weld it. If the epoxy fix dosent work I would just cut the whole AFM valve out and replace it with a straight section that I could slip fit then I know it would hold with a clamp.

Worst case I cut it and cant get the muffler back in then have to run straight pipes it couldn't be too loud with the cats still there and thankfully I'm not in California.

Sent from my Pixel 3 using Tapatalk

[KingLT1]

take the actuator off and have the afm valve tack welded in the open position?

Speed engineering x pipe is 189.00. another option to consider.