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Discovery II Overheating

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  #1  
Old 03-18-2019, 07:39 PM
Wagner Disco's Avatar
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Unhappy Discovery II Overheating

Hi everyone.
A this point we all have or experienced some type of overheating issue with our Discos and here the story about my Disco. Just finished replacing the head gaskets, shaved the heads at machine shop and did an entire tune up from oil to spark plugs including ignition coils and wires. Belt and belt tensioners, radiator hoses and new thermostat. Also replaced the crankshaft sensor and overhauled the entire engine. Radiator appears to be in good shape with no cracks or leaking and the water pump also appear to be pumping the flow accordingly. While replacing all fluids (including the coolant) I carefully blead the system to ensure all air was removed and guess what? After all that, I fired up the truck and went for a spin around the block. Half mile down the street temperature keeping going up almost overheating forcing me to turn around and go back home. On of those situations when you open a can of beer and scratch your head like what the hell.... After all that work, why still overheating? Bad water pump maybe? Clogged radiator maybe? Another thermostat somewhere inside the engine that I'm not aware of it? Open to any suggestions or tips at this point. Thanks in advance folks.









 
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Old 03-18-2019, 07:48 PM
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I'm guessing
A. Bad thermostat
B. Plugged radiator
C. Bad thermostat
D. System not full / bled / air pocket
E. Bad thermostat
Are you using an ultragauge or some other digital temp gauge?
 
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Old 03-18-2019, 07:54 PM
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My guess would be not bled sufficiently, especially since it sounds like you only bled it the once. Often it requires a couple attempts to get all the air out. Re-bleed and see what happens before freaking out. Search here for the many different ways many of our different members swear by.
 
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  #4  
Old 03-18-2019, 08:21 PM
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I agree with ahab.

what procedure did you use to bleed your truck?
 
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Old 03-19-2019, 07:06 AM
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Sounds like a stuck thermostat, that is the only thing that will make a truck overheat that fast. The bypass thermostat mod is a sure fire winner, but if you don't want to do that you can do an easy test. Check the top radiator hose, is it hot? If it isn't, you have a stuck thermostat. Autozone sells a $5 hose repair kit. Put the middle bushing in the two lower hoses where the thermostat goes, connect the upper radiator hose directly to the manifold outlet (its a little bit of a bend, but it will work). Fill with coolant with the top hose disconnected then connect it (shade tree air bleed). Run cool? You have a stuck thermostat. Now that you have the bushing in place, just put the bypass stat in place on the top hose. Done!
 
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Old 03-19-2019, 11:44 AM
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If the system is full, even with a little air, I agree the thermostat is suspect. There are reports of thermostats being bad out of the box.
 
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Old 03-19-2019, 07:16 PM
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Oh, and "viscous fan coupling" and make sure the electric fan is working.
 
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Old 03-20-2019, 06:11 AM
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No...you have to make sure the coolant cycles around the stat getting the air out before it will open.

I bet if you boil that stat it will open just fine.
 
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Old 03-20-2019, 06:17 AM
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Just because you added Coolant and open the bleeder does not mean the thermostat doesn't have air trapped around it. This is why I always say let it cycle. With all those new parts he could bleed it a couple times. Squeeze the hoses and raise the front end.
 
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