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Unread 02-09-2009, 08:44 PM   #1
Texas98ZJ
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1998 ZJ 
 
Join Date: Feb 2009
Location: Texas
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98 ZJ 5.9 overheating?

All,
First post! Need a little assistance here, my 98 ZJ 5.9 was consistently running 225 with the fan beating itself to death; but the temp never went higher. I noticed the upper radiater hose was pretty easily squished in my hand, but the lower was stiff as a rock. I thought radiator! The radiator is original and now has 140k miles on it. I pulled the radiator and it was in BAD shape, so I replaced it; filled it and burped the system several times. The upper radiator hose is now hot, but still not very firm to the squeeze; and temps are running right at 210. Lower hose is much harder than the upper. Problem? I told a mechanic to put in a 180 while in San Antonio because I spent a TON of time stuck in traffic. To me that means I shouldn't go above 180. SO - BOTTOM LINE : should the upper radiator hose be stiff to the squeeze? Would a non-hard upper mean the tstat is stuck closed? I'm now in El Paso and for those of you who know - it gets HOT HOT HOT down here in the summer and I don't want to be overheating. TIA for any help!
Rob

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Unread 02-09-2009, 10:49 PM   #2
-cAcHe-
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water pump? my upper hose is kinda squishy also...i have a 180 T stat on mine with an electric fan and it stays around 195 in the summer...those 5.9's have the electric fan right..maybe the an is going bad?
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Unread 02-09-2009, 11:39 PM   #3
Colorado 5.9
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If it's running at the 210 mark then that's about normal on a warm to hot day.

The fins on the pump might be worn down a bit do to cavitation. Especially if it's never been replaced.

When it's running though the upper hose should be tight. I'd try a new termostat first. Make sure you have a new cap too.
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Unread 02-09-2009, 11:46 PM   #4
97ZJMAN242
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the lower radiator hose is harder to squeeze because theres a spring like shape former that is stronger, takes more of a beating down there, the upper is squishy because its just the hose. but i would replace the tstat first simply because its around 5 bucks with a gasket....if its not it, it wasnt that expensive and you know its good...
if that doesnt solve your problem since you already replaced your old worn out radiator. i would def check your water pump.
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Unread 02-10-2009, 12:21 AM   #5
Colorado 5.9
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The spring is in the bottom hose because there is suction down there. If there was no spring, the hose would collaps tight.
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Unread 02-10-2009, 06:11 AM   #6
360limited
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My 5.9 runs between 210 - 220. That is when the fan turns on and off. I am pretty sure that is normal... I hit a tree and wrecked my radiator. So i have a new rad. new hoses and stat(180).
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