Exhaust rattle at idle during warm up

[cowboywildbill]

I have developed a rattle at warmup some where in the stock exhaust system. It happens at warm up and just above factory idle, if you give it just a little throttle. It does seem to happen less after warm up and idle is slower. But It still does it when I let off throttle while coming to a stop. It is a 2002 Dmax/allisn 3500 crewcab longbed w/21,000 miles on it.. I have been under it while it is running and can't find the source. I have checked all hangers and sheilds, even up on the engine but can't find where it is coming from. It resonates along the whole exhaust. I thought it could be a baffle in the muffler, but can't hear it there any more than at the front. I noticed it started happening about a week after putting on an ez-amp. I am not blaming the amp but it could make the engine idle just a little rougher and maybe that helps the rattle out. I can push on the exhaust system and make the rattle stop for a second or two. It really has me puzzled. It sounds like a shield rattleing, but I have grabbed all of them while it is running and can't feel any of them loose, nor stop the rattle. I am puzzled. Any one else notice a simular problem? I guess I could take it to the dealer and let them deal with it. I'm open for idea's or theorys. Thanks. "Wild Bill"

[mackin]

You might want to check the turbo down pipe bracket some have reported a crack and or broke off.........You will have to remove passenger side wheel well liner to get a good look at it...See my more DA Pics in the fuel filter file...Or you could just make an appointment at the dealer..........

MAC

[bearman]

I have a new rattle in my exaust, but I belive it is my new exaust brake. I think Mac may have your anser.
Cheers & Merry Christmas
Bear

[cowboywildbill]

Thanks for the info. I will pull the liner and take a look at the downpipe. I'll let you know what I find. Bill

[DmaxMaverick]

Mac has the right check for this, but DON'T remove the fender liner. Just lift it up enough to see the downpipe with a flashlight. You can see all the brackets. The one to check is the one just above the frame. If it has cracked, you will see it. I had mine welded and has been fine for more than 25K. The dealer offered to replace the downpipe, but welding was easier and just as well. Good luck.

[tpitt]

bearman,
I've installed at least four BD exhaust brakes on Duramaxs and have one that supposedly rattles. I've tried cutting 1/4' off of the adjustment nut and thought I had it whipped. (This preloads the butterfly more) The guy bought a 2003 and we transferred everything over to it and he says it still rattles. He left yesterday for a trip and I didn't have a chance to look at it before he left. When he gets back I am going to see what is causing this. If I can't fix it I am going to install another new brake on it and see if this cures the problem. I also have one on mine and have never had a problem with it. I do know that some of the Duramaxs have a resonation problem especially with non quality exhaust systems.
If and when I find out the answer I will let you know. These brakes should not rattle.
P.S. I also had one rattle on a Ford. I fought for hours trying to cure it. Come to find out the engine was running rough enough to cause this. By sound and sight I could not detect this. I did not put a scanner on this as by ear it sounded fine to me. (Learned a valuable lesson then) He finally got a check engine light, took it to the dealer and they found a slight miss that was causing this. They fixed it and no more rattles. tpitt

[bearman]

Thanks tpitt, that would be great if you found a fix, I will also have my dealer check to see if everything is OK. I will keep an eye out for your post's.
Cheers
Bear

[motovet]

My BD brake also has the rattle. I have just lived with it so far. I too would like to know the cause.

[tpitt]

bearman & motovet,
The first thing you guys can do is cut off 1/8" to 1/4" off of the adjusting nut. Apparently on the first brakes there wasn't enough preload due to the design of the ram and the bracket. I spent quite a bit of time on the phone with BD when I was chasing the rattle on the 2001, which was switched to the 2003. This is why I stated supposedly had a rattle on the 2003, I couldn't hear it any more on the 2001. The customer changed his own exhaust over to the 2003, and did have a rattle with the brake hitting the frame. I just redid the X-monitor, brake plumbing, and easy amp.
You don't have to pull the brake clear off to do the adjusting nut. You can pull the ram itself. When you get done with this, reset the idle pressure to around 18# I do this with the brake on at idle, and adjust the bolt on the bottom of the bracket. The high side is is adjusted at the compressor. Sorry to be so long winded, but this is what I would try first. When he gets back I will confirm if it is the brake rattling for sure. Terry

[cowboywildbill]

Thanks for all of the input and advice. I got back under the truck today and I found that the shield on the turbo downpipe was just barely touching the trans dipstick filler tube. I gently pushed them apart, and now the rattle appears to be gone. I couldn't find a crack in the bracket, I was looking from underneath, If I was looking at the right bracket, it was connected to the side of the bell housing. I'll let you know if the rattle stays gone. Thanks again for all of the help. Have a Safe and HAPPY NEW YEAR! from "Wild Bill"

[ 12-28-2002: Message edited by: Cowboy Wild Bill ]</p>

[Applecore]

Just had Banks exhaust system installed, I didn't notice the bracket cracked then. It is the one just ahead of the exhaust pipe clamp. Hard to see if you don't remove the fender liner. I had boost and Exhaust Temp Gauge installed yesterday, when we removed the fender liner, it was easy to see the bracket was seperated about 1/4". I will be talking to my dealer soon.

[cowboywildbill]

I test drove the truck and most of the rattle is gone, but I can make it rattle by putting it in reverse and barely stepping on the throttle to back up. I will be pulling the fender well out next chance I get and have a look at the bracket. thanks. It sounds like there might be a bunch of them out there that are cracked or broken. "Wild Bill"

[CPMac632]

Mine is broke but you really don't have to pull the liner to see. Just above the rear of the passenger manifold there is a tab bolting the downpipe.

[motovet]

Thanks Terry, I will have a look under there.

[cowboywildbill]

It started to rattle again, I will pull the wheel well liner tomorrow and see if it is the bracket. Wow this is getting annoying! I guess if the engine was as noisy as all of the other brands are, I wouldn't notice the rattle as much, because I wouldn't be able to hear it over the regular diesel noise. I'll let yall know what I find . Bill