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Unread 03-04-2009, 02:31 PM   #1
danthman
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overheating 87

i have, what i think is a unique problem. my jeep starts to overheat in 4th and 5th gear at hwy speeds, well around 50, around 2000 rpm. now in 4L crawling in the desert at the same rpm, it stays around 210. why would this happen? it has a mopar fuel injection kit, a 185 degree t-stat. could it be the transmission heating up? or sensors going out? vac-leaks?

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Unread 03-04-2009, 06:49 PM   #2
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wow, nobody has any ideas?
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Unread 03-04-2009, 07:03 PM   #3
rustywrangler
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remind me, is that a closed system or an open system(has a rad cap and overflow tank)

how do you know it is overheating??? The temp gauge goes up??? boils over???

If it is happening at speed but not going slow, I would suspect the fan clutch.
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Unread 03-04-2009, 07:10 PM   #4
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If you have a 185 Tstat and it's 210 while crawling it's overheating there as well. The main difference between that and highway is that you're running sustained RPM's on the latter and likely not sustained while crawling, thus more heat generation. Have you flushed your cooling system? Are you sure the Tstat is good? You can test it with a pan of water on the stove with a cooking thermometer to see at what temp it actually opens up.

I have heard of some weird cases where the inside of a radiator hose detaches from the hose body, a flap if you will, effectively operating as a valve choking off coolant flow under higher RPM's so you might want to check all cooling hoses as well. How old are the hoses? Just some suggestions.
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Unread 03-04-2009, 07:15 PM   #5
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if the lower hose is spongy it could collapse at higher rpm. back in the day they came with a spring inside to keep this from happening. the newer hoses might not need them but im not sure. rev it up when its hot and take a look at the lower hose.
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Unread 03-05-2009, 06:41 AM   #6
danthman
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Quote:
Originally Posted by rustywrangler View Post
remind me, is that a closed system or an open system(has a rad cap and overflow tank)

how do you know it is overheating??? The temp gauge goes up??? boils over???

If it is happening at speed but not going slow, I would suspect the fan clutch.
it has an overflow tank, and the rpms can be the same. with my gears i rarely need to get it above 2000 rpm. i dont think its the fan clutch, it was checked and it was good.
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Unread 03-05-2009, 06:44 AM   #7
danthman
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Quote:
Originally Posted by UnFocused View Post
If you have a 185 Tstat and it's 210 while crawling it's overheating there as well. The main difference between that and highway is that you're running sustained RPM's on the latter and likely not sustained while crawling, thus more heat generation. Have you flushed your cooling system? Are you sure the Tstat is good? You can test it with a pan of water on the stove with a cooking thermometer to see at what temp it actually opens up.

I have heard of some weird cases where the inside of a radiator hose detaches from the hose body, a flap if you will, effectively operating as a valve choking off coolant flow under higher RPM's so you might want to check all cooling hoses as well. How old are the hoses? Just some suggestions.
210 is about the norm for an I6, isnt it? i havent flushed the system and the t-stat is about a year old. ill look at the lower hose this weekend...
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