Originally Posted by dons2346
The new manifolds are a 2 piece afair. If you replace one, replace the other one also. When I had it done, the manifolds were, I think $600 and labor was the same. Lucked out with no seized bolts.
Always learn something new reading this forums! Our ISL, built in Sept of 2003 (And was serial number wise one of the last 60 CAPS era ISL's built before shift to Common Rail and Variable Geometry Turbo ISL's), had a Two Piece Exhaust manifold as OEM.
I believe the ISC, which the ISL is based off of, had a long product run. With the block itself preceding the newer electronics that made it the ISC vs the 8.3 Mechanical. Did the early ISC's have 'one piece' manifolds?
And frankly, since the ISL's also seem to still get cracked/warped exhaust manifolds even with the 'two piece' - not sure it's something I'd consider new and improved...
IMO, Cummins knew the Exhaust Manifolds were not up to long life, and have never redesigned them for a pure 'parts replacement and hopefully labor too' revenue stream. No excuse to not CPI and have improved replacement Exhaust Manifolds for their ISC's and ISL's.
And as luck would have it, I still have never found a company that made an improved After Market Exhaust Manifold for the ISL. To me, this would be good revenue product for a company like PDI or Pittsburg Diesel, etc... I believe many owner's would pay more for a better alloy constructed, and hopefully even better ported/polished, replacement Exhaust Manifold. (Well, I know I would have...)
I've told my wife that it will not be 'if' but 'when' we need to go in for another replacement exhaust...
And yes, proper cooling down periods can help on this, and I do believe I follow those techniques. And since I was pulling a pretty good grade going from Bishop to Reno on 395 with outside temps in the low 100's when ours exhaust cracked (Could hear the noise difference from the engine immediately, and yep it was # 3 that cracked.) - cooling down had nothing to do with it. We running the engine with coolant temps maybe 2-3 degrees (Silverleaf) higher then normal. I've since added a VGT gauge to my dash, to monitor exhaust heats vs coolant temps... Stock engine, but possible it was working a bit too hard on that pull, and the exhaust temps climbed too high... So I now drive more by VGT, then by Coolant Temps... And sure, practice good manual down shifting to keep the RPM's in the happy range...
After Market companies are missing an opportunity, by not targeting the ISL and even ISC - as just a few million of them are running in Medium Weight trucks and RV's
Best to all, travel safe,