cjlennon623

Hey Folks, Thank you for taking the time to read this post. I have a problem with a 1996 Mack 427 engine and I am lost. The original driver complaint was exhaust temperature had been running hot in the past but has settled down. Loss of power and excess smoke was also now occurring. After tearing the top end off the engine, I found that the exhaust manifold had gotten extremely hot where it has burned off that rust coat that forms on these cast iron manifolds near the #5 cylinder. It got so hot that it started to melt the port that attaches to the turbo. The cast iron inside the exhaust manifold was actually turned to molten metal. My first thought was that I had a leaking injector but they were tested and are good. Next, I noticed that there was "soft" (powdery) carbon in all exhaust ports as if all the cylinders were burning at a normal temperature. So, my next thought was that maybe this "hot" condition happened some time ago and the condition clear up but the damage that was done previously was just now surfacing to cause problems. One note here. A year or so ago, the exhaust pipe blew out and had to be replaced. The boss fixed it but took off one of the mufflers and stack and converted it to a single exhaust system. After the driver complained about loss of power, it was converted back to dual exhaust. Could this have caused the engine to run hot? So, now my question is, what condition can cause one or two cylinders to run extremely hot on a 427? There is definitely heat damage to the exhaust manifold and turbo. It does have an exhaust brake but that appears to be OK - open at rest and no sticking linkage. What's left that makes a diesel run extremely hot? It does have a computer but I believe that it only controls the rack and does not control each cylinder individually so I don't think that is it. All that is left is the pump. Any thoughts? Anything will help. Thank you to all in advance! Chris