We had an exhaust leak about a month ago on our ISL 400. It was the #3 and #4 cylinder. I drove it about 400 miles without any problem before we got it fixed. I could see soot around the manifold and also engine noise was louder. I also could see where the gasket was missing.
I had a Cummins shop repair it. Luckily the manifold wasn't cracked, but 6 bolts broke when they were taking the manifold off. I was told that this was quite common and they had no problem getting the old bolts out and new ones put in.
I now have more power and engine braking is better also.
