Causation of magnum head cracking.
Lets chase this rabbit down the hole even further.
Clogged cat, leads to higher cylinder temps, leads to higher exhaust temps, leads to cracked exhaust manifolds or leaky gaskets, which leads to a slight amount of winter air to go in through the leak before the compression cycle, which is too cold and makes the exhaust valve crack....
Clogged cat, leads to higher cylinder temps, leads to higher exhaust temps, leads to cracked exhaust manifolds or leaky gaskets, which leads to a slight amount of winter air to go in through the leak before the compression cycle, which is too cold and makes the exhaust valve crack....
Champion
Joined: Jun 2004
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From: Ft Campbell, KY/TN
I blame all politicians. I have not seen one that realizes that they are PUBLIC SERVANTS. They think it is a status symbol.
Legend
Joined: May 2005
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From: Central Oklahoma
Lets chase this rabbit down the hole even further.
Clogged cat, leads to higher cylinder temps, leads to higher exhaust temps, leads to cracked exhaust manifolds or leaky gaskets, which leads to a slight amount of winter air to go in through the leak before the compression cycle, which is too cold and makes the exhaust valve crack....
Clogged cat, leads to higher cylinder temps, leads to higher exhaust temps, leads to cracked exhaust manifolds or leaky gaskets, which leads to a slight amount of winter air to go in through the leak before the compression cycle, which is too cold and makes the exhaust valve crack....
Toe bone connected to the foot bone
Foot bone connected to the leg bone
Leg bone connected to the knee bone...
Administrator
Joined: Apr 2010
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From: Clayton MI
It's George Bush's fault. Along with crashing the economy with his trade policies, he sneaks around at night, pulls heads off 2nd gen dodge trucks, and unevenly heats the valve seats, causing them to crack.
Retired Moderator - RIP
Joined: May 2008
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From: NH
The head castings are poorly designed, that's a give in. And , I do state all the time, to replace the plenum BEFORE the cat gets clogged and your heads crack. Sometimes I wonder which one really comes first(chicken or the egg?). I'm pretty convinced it's the plenum first and then clogging cat(not just bad head castings). Notice I said "clogging" cat, not "clogged" cat. As that heat rises and backs up into the exhaust manifold (slowly but surely) those hotter and hotter heat cycles can't be good on a head that is not very well cast/designed to begin with.
All I know is, that before I found DF, my 98 had two CC's put on it under warranty and was given the death flash. And later on when I found DF. The test's that I performed on it, pretty much confirmed the heads were cracked. It got wrecked before I could could confirm anything. But my 2000 with alot less miles on it was saved thank god. I did replace the plenum right away when I bought it, and the same tests that I performed on the 98 came up negative as opposed to positive.
Anyway, I still wonder sometimes, if it's the plenum first, a bad cat design , cracked heads, or simply the crossfire problem. I don't think we will ever know. As long as we love how these trucks look , who cares right? lol
All I know is, that before I found DF, my 98 had two CC's put on it under warranty and was given the death flash. And later on when I found DF. The test's that I performed on it, pretty much confirmed the heads were cracked. It got wrecked before I could could confirm anything. But my 2000 with alot less miles on it was saved thank god. I did replace the plenum right away when I bought it, and the same tests that I performed on the 98 came up negative as opposed to positive.
Anyway, I still wonder sometimes, if it's the plenum first, a bad cat design , cracked heads, or simply the crossfire problem. I don't think we will ever know. As long as we love how these trucks look , who cares right? lol
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From: NH
Yea, but which one? LOL
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From: Riverton, UT
From what I have seen cracking of the heads on the 5.9L magnum motor is due to the casting. The head was made to run at 180 degree F, yet the motor is now running 195+ constantly because of emissions. The head was never made to originally run at that high of a constant temperature. They where built to run cooler so as the spacing was made. But then they heated them up but didn't change the diameter between the heads, it was a stupid engineering consequence.
So after years of heat, and/or abuse there isn't enough material between the valves to with hold the added stress or added heat so they crack. Call any good shop and that is what they will tell you, not to mention a metal worker could tell you.
It really is very easy to understand when your looking at a set of cracked heads....IMHO......That's why I push for owners to use 180 degree F T-stats over OEM.
So after years of heat, and/or abuse there isn't enough material between the valves to with hold the added stress or added heat so they crack. Call any good shop and that is what they will tell you, not to mention a metal worker could tell you.
It really is very easy to understand when your looking at a set of cracked heads....IMHO......That's why I push for owners to use 180 degree F T-stats over OEM.