hi like i said i need your guys help to diagnose my problem. so i have a 96 4.0l and it was running very badly i got home turned it off and bam! 2 gallons of coolant on the ground in one second. i was wondering what caused my radiator to pop. and what is a sign of a cracked or blown head? the jeep would barely do 10 mph and it was gutless and would get boged down when i would push the gas.

i am just asking your guys oppinions before i start tearing into the top end of the motor.

 

Sounds like either the head or the head gasket. I had a similar thing happen a couple of years back, and it was the head gasket. As soon as I turned it off, the coolant would spray out really fast.
Then again, it could also be something a little less drastic. I had a severe coolant leak last week, turned out to be a corroded water pump and the thermostat rusted open!
I think you should get a mechanic to look at it... We can speculate what we think it is, but we can only really diagnose it by seeing it.
Good luck mate.

 

compression test?

 

What caused the radiator to pop?

Well, the radiator/water pump/cooling fans only have an effect while the engine is running. When you shut the engine off, the coolant temperature will actually RAISE a significant amount as it soaks up the heat from the engine block without any means of cooling back off.

So, when your Jeep overheated, and then you shut it off, the coolant temperature increased too much and the pressure was too much for the radiator cap to hold, so it released - just like it's supposed to, that's why there's a little spring on the cap.

Example: (Skip to 3:25)
www.youtube.com/watch?v=BCYKgj8FKFA
(how the heck do you embed youtube on this forum?)

In this case, it was the upper radiator hose that blew, right where it goes into the intake. You can see as soon as the motor seizes up, that hose starts to expand like a balloon, then explodes.

Some race cars have electric water pumps for this reason - they can keep the coolant flowing through the radiator so the fan can cool it off after the engine has shut down.


As far as what caused your engine to overheat in the first place... could be a lot of things. Failed water pump, plugged radiator, air pockets in the system, blown head gasket, etc... lots of things to look for.

 

That does not sound like a bad head/head gasket to me at all. I would start with simple things first; rad cap, hoses, etc. Of course if you overheated the engine by loosing the coolant then you may have to look into the head. But that would be a consequence not the root cause.