Exhaust rattle on cold start?

[taco-13]

Nope.
Had my entire exhaust replaced a few months ago. Rattle came back. Inherent problem with the valves in my opinion. You are lucky and got one that hasn't failed... yet.

Pretty much same deal. Exhaust was replaced a few months back. Made no difference. Waste of time.

 

[blaiseam]

Every time I start the truck I cringe, almost considering the Magnaflow just to get rid of it....

 

[HighwaySentinel]

So, I wonder what goes on in the system that stops the rattle after idling for a few minutes? Heat expands and fills in a small gap?? Should it take 2-3 years to come up with a fix?

 

[Hemmy]

So, I wonder what goes on in the system that stops the rattle after idling for a few minutes? Heat expands and fills in a small gap?? Should it take 2-3 years to come up with a fix?

Roush has been using an active exhaust system since around 2015. My Dad has a Roush phase 3 with the active exhaust and never had this clicking sound. Roush's setup can't be any different than what Ford's is.

 

[Syberspace]

Roush has been using an active exhaust system since around 2015. My Dad has a Roush phase 3 with the active exhaust and never had this clicking sound. Roush's setup can't be any different than what Ford's is.

Agree... Never had an issue with me GT350 or any car with an active exhaust.
The rattle is less pronounced on my replaced exhaust and is now rattling only when cold. The original exhaust did not rattle cold, but only when warmed up and at idle. Who knows the fix, but I am tempted to pull it apart myself.

 

[blue22raptor]

I noticed on cold starts, that when I barely press on the gas pedal (not even enough to raise RPM’s), the exhaust sound changes and the rattle sound goes away. I think I hear the exhaust flaps move, mechanically. The computer in the trucks must be doing something to the valves. I may try to have my wife press on the accelerator while I unplug the electrical connectors…
maybe I can get them to stay in whatever position stops the rattling...it is very embarrassing, every single time I start the truck!
Once the rattling stops, it does not come back, until I start the truck again…

 

[Brody Goble]

I noticed on cold starts, that when I barely press on the gas pedal (not even enough to raise RPM’s), the exhaust sound changes and the rattle sound goes away. I think I hear the exhaust flaps move, mechanically. The computer in the trucks must be doing something to the valves. I may try to have my wife press on the accelerator while I unplug the electrical connectors…
maybe I can get them to stay in whatever position stops the rattling...it is very embarrassing, every single time I start the truck!
Once the rattling stops, it does not come back, until I start the truck again…

Exactly the same as my truck. And it’s not even really related to cold start but just every start. Loud enough that people ask what the sound is!

 

[blue22raptor]

So…I unplugged the wiring harnesses from both exhaust valves today. Truck started up with no rattles several times throughout the day. The exhaust was stuck in whatever mode it defaults to when the truck is shut off. These valves are more active than I imagined. The truck now sounds like it’s in ”sport” exhaust mode.
Apparently, the exhaust is constantly moving to produce the sounds we hear. I plugged them back in and had a second hand rev the engine, while I watched the exhaust valves, with the expanded metal cage removed. The valves opened every time we raised the RPM’s. They shut when returning to idle….
The rattling must be an unexpected result of a programmed start up procedure...that is the only thing I can think of, as the rattling never happened with the valves unplugged. It happened EVERY TIME with them plugged in.

update next day: tried it again. No more rattling. Truck sounds good and I believe the shudder when stopped in gear has gone away! Going to leave them unplugged until a permanent fix is available!

 

[blaiseam]

So…I unplugged the wiring harnesses from both exhaust valves today. Truck started up with no rattles several times throughout the day. The exhaust was stuck in whatever mode it defaults to when the truck is shut off. These valves are more active than I imagined. The truck now sounds like it’s in ”sport” exhaust mode.
Apparently, the exhaust is constantly moving to produce the sounds we hear. I plugged them back in and had a second hand rev the engine, while I watched the exhaust valves, with the expanded metal cage removed. The valves opened every time we raised the RPM’s. They shut when returning to idle….
The rattling must be an unexpected result of a programmed start up procedure...that is the only thing I can think of, as the rattling never happened with the valves unplugged. It happened EVERY TIME with them plugged in.

update next day: tried it again. No more rattling. Truck sounds good and I believe the shudder when stopped in gear has gone away! Going to leave them unplugged until a permanent fix is available!

Ok awesome info thank you.

So put the truck in Sport Exhaust (if i want it always on sport), unplug the harness (with truck on), and turn the truck off this should fix the problem?

 

[Antho]

If I had to guess..

In quiet mode, the valves are closed and opens more based on throttle position.

normal mode is 1/4 open and opens more based on throttle position.

sport open 3/4 of the way and opens more based on throttle position.

Baja mode is fully open.

Kinda makes me think ford removing quiet time exhaust start was an attempt to eliminate the rattle.


actually found a good video. Based on a mustang but I would bet it’s the same.