exhaust manifold

[jgh]

1999 5.9 275 hp, cracked exhaust manifold. What is recommended replacement, OEM or aftermarket(claim more power and less heat). any ideas welcome

[J Walker]

If you go with a stock exhaust manifold be sure and get one that is in three pieces instead of the one piece that is supplied on you engine when new. It will help to relieve stress and reduce the chance of cracking. I would stick with the stock three piece manifold. Going the header route to increase HP has many opinions and some risk and I would stay away from it.

[GreaTOne65]

I had a cracked manifold on my 5.9L Cummins, last year before I started my annual trip to AZ. After reading about the 3 piece performance manifolds, I figured what the hell, let's go for it!. Problem. With out changing all the intake and exhaust plumbing, which can be done, if you have the time, on my Freightliner chassis, there was going to be a problem with the location of the turbo, it moves it forward about 6 in. So, being in kind of a time problem, DW wanted to leave for AZ. went to my local dealer and bought an OEM, it is a 2 piece design, same as my original. The original made 90,000 miles, so that's what I did, and I'm not sorry, it was a simple operation to change, the reason being, I had no problems with the manifold bolts, they all came out, what a relief.

Ok, that's my story. Good luck with what ever you do.

Dale

[DARRELL1953]

I had a 99 Itasca with cummins 275. Noticed soot around a couple of ports and removed the manifold. Bolts were very difficult to remove.(manifold shrinkage). No cracks. I slotted the bolt holes out and port matched the manifold.Cummins wanted 275.00 for new 2 piece manifold.Had my manifold been cracked,I would have slotted the mounting holes on the new one and been done with it.( very common prob with this engine)

[J Walker]

Dale, Thanks for sharing your experience. I would do exactly what you did and stick with the two piece OEM exhaust manifold. The cost of re-plumbing the exhaust would not be worth it. I will not be surprised if my 2000 ISB 260 HP has an exhaust manifold problem in the future and being well informed is always a help.

[JBDISCOVERY]

I had the same problem with a cracked manifold. Replaced with OEM from Cummins. Very easy swap out. No problems with the turbo or with the bolts. Have put 10,000 miles on the engine since with no problems. Seems this is something that just happens.
Seems that I remember a saying that says it all.
Regards,
JB

[jauguston]

Usually the cracked one is one piece. Our last coach one was('99 ISB). the replacement was two piece.

Jim

[GreaTOne65]

The one I replaced was two piece, was really surprised to see it was cracked. I have run Cummins engines in the farm tractors I had, and never had exhaust manifold problems, but they are hanging out in the breeze, unlike the Motorhome. The 454 that was in my Pace Arrow, broke the manifolds, I replaced them with headers, big mistake! Could never stop them from leaking.

[jgh]

The manifold that I had to replace was 2 piece. new one is 2 piece hope it lasts.