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Cracked Block?

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So, I'm driving my truck, and my fan belt came off. I knew the belt came off cause the "BATT" light came on, and I lost power steering.


Because I was close to home I chose to drive it home.


steam started to come out of the hood, then water.


Shortly after that a loud "BANG", engine still was running smooth. So I thought I popped a radiator hose.


I did coast as much as I could.


When I got home, I opened the hood and found the broken belt. Then I looked for a popped hose, they all looked good. There was steam coming out of the radiator (near a hose), may have cracked that.


What has me worried is, that loud BANG,(I thought it was a hose) now I wonder if that was a water passage that broke open..


What do you all think?


Oh, this is on my classic JEEP Truck, its a I6 4.0L

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Bad decision. Could be anything ranging from bad to worse since you obviously waaay overheated it. Suggest eyeballing for obvious damage, then fitting a new belt and start 'er up, if it will. You will soon know the problem. Good luck mate........


Oh, and check your oil for water bubbles on the dipstick.

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Check the coolant to see if it's gotten darker. Do an oil change to see if there's anything else in it. When we drained the oil out of my brother's motor that had seized, about 8 quarts of liquid came out. Then when we drained the coolant, we got almost a gallon.

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not yet, it was late when i got home..


I just remembered, the water hoses had pressure. If the block cracked, there would be no pressure in the hoses, right?


I was going to build a nice 4.0 Stroker for this truck, later. I may be doing a stoker install sooner...

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Ok I checked the oil, it looks good.


Looks like the broken belt was captured by a pulley and whipped around, it smashed a fan shroud. That may have been the “Bang” I heard.


After removing some items, I inspected the radiator where it was spewing steam. I thought I would find a relief valve, but I saw nothing like that, so I'm sure I popped the radiator.


I installed a new belt, but something is odd..


According to the belt diagram: the “ribbed” side of the goes around the crank, this is odd cause the crank is smooth. And I can’t get the belt tight, the PS pump is as far as it will go, and belt is just a bit loose. Is there supposed to be a grove pulley around the crank?


If the crank is supposed to have groves, then that part of the crank pulley fell off, and that would have been the bang sound I heard.

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cool. either you have been driving for a very long time with worn parts and signs of problems, such as squeaking or other things. or your belt got all hung up when it came off and wrapped around the balancer and damaged it. either way the point is, it is never ever good to keep driving in these scenario's, at least get out and assess the situation. pull the broken belt parts out and drive home watching the gauge and stopping when it gets hot. and i can basically guarantee you cost yourself more money now because they're is more wrong now than if you stopped.


i can't believe how many times i see this in the shop, people just figure its more important to keep driving and get home before dealing with the problem.

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  • 2 weeks later...

Ok, here is what I figured out.


My JEEP has always had a vibration, I did ignore it. I Figured when the engine blew, that I would just put a stroker in. (I use the jeep for work, but it is a toy, and money I have. I put a 550+HP HEMI in my RAM, and I'm having a 520Ci monster built for my 79' PowerWagon, I have lofty goals for this jeep)


any way, on the Vibration, the Crank pulley / Dampener must have been on its way out. It most likely wobbled or walked enough to cause the belt to pop off. I continued to drive home, when the dampener part of the pulley fell off. I heard the bang, I thought it was a hose, but turned out the dampener pulley hit under the jeep. It was at that point the engine actually ran smooth, cause the engine was now running real nice, I chose to limp it home.


Got home, saw steam shooting out of the radiator, I was hoping there was a release valve there, no luck. I Popped the radiator.


So, I replaced the crank pulley, Installed a new fan belt, and installed a new radiator.


The jeep now drives super smooth, everything seems fine so far. I'll Commission the construction of a 4.0 Stroker motor in a few months for my jeep.

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