thenrie

I installed a BD exhaust brake on my truck last year. Just noticed I now have an exhaust leak between the head and exhaust manifold on #5. Apparently the pressure from the exhaust brake has overcome the gasket. In talking to a mechanic, he said that he has often encountered a problem on the Cummins 5.9, where the manifold warps when removed, making it difficult to eliminate leaks when reinstalled. Anyone else had this issue? I had the engine rebuilt about 43K miles ago, so it's possible the manifold was sufficiently warped at that time that it didn't seal properly. Thoughts about buying an aftermarket exhaust manifold have come, but I've been told there is no performance gain over the stock manifold.

Any thoughts or advice?

Fordzilla

I've run into the same problem in the past with 300 CID Ford truck gas engines...I wound up milling the head and manifold flat, then reinstalled...You may not have to mill both, but with the manifold removed and the surfaces cleaned, you can check for warping with a straight round bar......Ben

StealthDiesel

An exhaust brake is unforgiving on any exhaust joints upstream in the exhaust system.

Most likely your exhaust manifold bolts came loose and the gasket blew out.

Cummins redesigned the 2003+ 5.9L common rail exhaust manifold several times over the years.
They added more material each time but I recommend an aftermarket one for a truck that has an exhaust brake and tows heavy regularily.

Any aftermarket one will do, they are all similar. Check all the turbo and ex manifold bolts every oil change.

thenrie

Spoke to my mechanic. He said it is likely the exhaust leak occurred because the exhaust manifold was not perfectly straight when it was bolted back on after my engine rebuild a couple years ago. He said it is almost certain that I'll need to replace it anyway, so he recommended going with an aftermarket unit.

There is a pretty wide range of prices for the aftermarket exhaust manifolds for the Cummins 5.9. The cast iron ones seem to be made in two-pieces to allow for expansion and contraction without cracking. Any thoughts as to how a two-piece design would handle the pressures from an exhaust brake? I'm looking at the AFE stainless steel cast unit (one-piece) as compared to the BD and ATS ductile iron units (two piece). There is also the AFE unit that appears to be welded steel, like a gas engine header, but it's about double the price. With a stock turbo, I doubt I could get any extra performance out of that last one. From my younger days, I remember that the cheapest and best performance improvement one could bolt onto a gas engine was a good set of headers. I don't know how that relates to a diesel engine with a turbo on it.

Comments and suggestions appreciated.

thenrie

I just received my BD Pulse 2-piece exhaust manifold. Before I ordered it, I asked a dealer whether I should be concerned about exhaust leaks with the two-piece design, since I'm using an exhaust brake. I was told it is not a concern and not to worry about it. However, now that I have the manifold in-hand, I find the expansion joint is nothing more than a machined slip joint that I can easily pull apart with my bare hands and little pressure. I ask myself how in the world does that not create an exhaust leak, especially with the high back pressure caused by an exhaust brake? I mean, I blew out a manifold gasket! How does the pressure not blow past this slip-fit joint?

I'm hoping somebody with more knowledge/experience than I have can give me an explanation that will convince me this manifold will work with my exhaust brake!

thenrie

I talked to BD Diesel Performance this morning regarding the BD Pulse 2-piece exhaust manifold. The technician said the slip fit is designed to allow for expansion and contraction without cracking the manifold or damaging the head mounting bolts. He said that when cold, the slip fit is not tight, but that carbon buildup over the first few miles of use will seal the joint against leakage. I was satisfied with this explanation, so I'll go ahead with the installation. He said they have both two and three piece manifolds on trucks with exhaust brakes and the back pressure is not enough to overcome the carbon buildup inside the slip joint.

I'll report back on this thread to give my evaluation of the installation process and performance in the next couple weeks.

StealthDiesel

The 2 and 3 piece aftermarket Cummins exhaust manifolds have been around for nearly 30 years. I have had a 3 piece ATS exhaust manifold for over 12 years and an ex brake with zero issues with it.
The multipiece ex manifolds are so easy to remove/install. Just use a rubber mallet to adjust/align if needed.

Getting the aftermarket cast iron ex manifold ceramic coated is nice if you plan to keep the truck.

As you mentioned, there is zero performance gain with an aftermarket ex manifold.

thenrie

I made a video about the install of my BD Pulse exhaust manifold on my 2005 Dodge 3500. The install wasn't without its difficulties. Namely, BD did not clearance some of the bolt holes sufficiently to get a wrench around the manifold bolt heads. I had to create a special slim socket to get to one of them and on another, I couldn't get a socket or any kind of wrench other than a small open-end on the bolt head, so I couldn't check the torque. After several thousand miles I am still hearing an exhaust leak when I use the exhaust brake. I can hear the high squeal, but I haven't yet been able to identify for sure the source of the leak. I think it's the slip joint. As soon as I figure it out for sure, I'll report back.

Here's the video link: