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4.0 operating temp


 
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poisoncherokee
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Joined: 24 Aug 2006

PostPosted: Sat Aug 26, 2006 4:40 pm    Post subject: 4.0 operating temp Reply with quote

how hot should the 4.0 operate at.. Im working on redoing my cooling system cause i had an over heating problem.. I have a temp guage now and wanted to know where about it should be.
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88WOWJ
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Joined: 12 Aug 2006
Location: Hinesville Ga

PostPosted: Sun Aug 27, 2006 12:50 am    Post subject: XJ Heat range Reply with quote

Most operate at or near 205-210 degrees. I dont know what year yours is
but the stock thermostat is 195 dgrees. Dont change your T/stat to a cooler one as that will cost you in gas. The probelm with XJ heat is a flow problem in my opinion, moving more water means cooler in my book.
You hear during the first heat wave anywhere about the high temps XJS get to. People talk about 3 core rads and such.To me a 3 core rad is a waste, more water moving at the same speed doesnt mean cooler conditions. My 1988 XJ has astock T/Stat, a 2 core rad with the exception of a 14 inch electric fan instead of the centrificul fan and clutch assembly.
I still have my 13 condenser fan as a backup.It comes on at 206 degrees.
My top temp ever hit has been 206 with both fans running. The second fan ran for about 10 minutes. One company Hesco makes a high flow water pump and T/ stat housing.Think of water in a cooling system as a traffic jam. The more cars the slower you move.Like the 3 core rad the more water the slower it moves.
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Rocklizards panels, Tomken rear bumper and front Tow brackets, Rocket air intake, 2 inch lift,
30x950x15, 1991 coolant system with electric fans, 8,000 mile marker winch
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IBTJn
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Joined: 31 Dec 2004
Location: Just Outside of Portland, OR

PostPosted: Sun Aug 27, 2006 8:09 am    Post subject: Re: XJ Heat range Reply with quote

88WOWJ wrote:
Like the 3 core rad the more water the slower it moves.

Is it just me or does this logic not make sense? ??? If this were true, plants would NOT go bigger on their cooling towers and boilers to handle their processes. Rolling Eyes
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JtotheEEPxj
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Joined: 01 Nov 2005
Location: Antelope, CA

PostPosted: Sun Aug 27, 2006 10:58 am    Post subject: Reply with quote

Doesn't make much sense to me either. Depending on the vehicle, it can work both ways, but it seems that the more water you have in your radiator, the more water there is being cooled by air flow at one time. The water pump and condition of water ports in the motor decide how much water flows through, and that wouldn't change by stepping up your radiator size. ALso, fan clutches drag the motor down power wise, but cool better and more efficiently than any other type of fan, i'd recommend keeping or using one whenever possible.

My 93 4.0 runs right around 210 depending on the weather, that's normal for any of em.
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"If it ain't dented, ya ain't wheelin' hard enough"
-1993 XJ, 4.0, 5 spd, 4.5" lift, 32's, Warn bumper, JKS link kit, skid plates, D30 & 8.25 w/ 4:56's & Detroit locker
-1965 Ranchero, new paint & interior, 302, C4, torque thrust II whls
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ThePhantum
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Joined: 23 Jan 2004
Location: I knew it...I'm surrounded by Assholes!

PostPosted: Mon Aug 28, 2006 2:23 pm    Post subject: Re: XJ Heat range Reply with quote

IBTJn wrote:
88WOWJ wrote:
Like the 3 core rad the more water the slower it moves.

Is it just me or does this logic not make sense? ??? If this were true, plants would NOT go bigger on their cooling towers and boilers to handle their processes. Rolling Eyes


The speed of coolant moving through the radiator will change with a 3 core. It's basic fluid dynamics: push a volume of liquid from a small pipe to a big pipe and it slows down. Move that same volume from a big pipe to a small pipe and it speeds up.

A three row radiator has more volume than a 2 core. When the coolant moves into the radiator, that volume of coolant will have more room to flow, causing it to spread out and slow down...which is the point. The longer the coolant is in the radiator, the more it cools before going back to the block.

Since the coolant tubes/water jacket in the block have not changed in size, regardless of radiator size, the water pump is going to move the same amount of water through the block at the same speed it always did, so it's hardly a waste. Couple a 3 row rad with a ported thermostat housing and you will drop 5-10 degrees in temperature. Mine runs at 195-200 and that's with the stock fans. Wink
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IBTJn
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Joined: 31 Dec 2004
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PostPosted: Mon Aug 28, 2006 4:03 pm    Post subject: Re: XJ Heat range Reply with quote

ThePhantum wrote:
...It's basic fluid dynamics: push a volume of liquid from a small pipe to a big pipe and it slows down. Move that same volume from a big pipe to a small pipe and it speeds up.

A three row radiator has more volume than a 2 core. When the coolant moves into the radiator, that volume of coolant will have more room to flow, causing it to spread out and slow down...which is the point. The longer the coolant is in the radiator, the more it cools before going back to the block.

Since the coolant tubes/water jacket in the block have not changed in size, regardless of radiator size, the water pump is going to move the same amount of water through the block at the same speed it always did, so it's hardly a waste. Couple a 3 row rad with a ported thermostat housing and you will drop 5-10 degrees in temperature. Mine runs at 195-200 and that's with the stock fans. Wink

Exactly. I can think of at least a couple more reasons why (if spending the money on a new rad) going to a 3 core would be a good move. Simple flow dynamics and heat transfer alone would dictate a 3 core over 2. I too hardly would consider it a waste.

Whew...I thought I must have been going nuts or something. Or that all these years of working in the industrial water treatment industry (i.e. boiler, towers, etc.) I was giving wrong info'. Confused

Wink
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