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post #1 of (permalink) Old 12-30-2002, 10:44 AM Thread Starter
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Over heating solutions?

Took my CJ up to the SD Black Hills this weekend for some 4 wheeling fun. Air temp 60*, humidity about 25%. My Jeep ran cool (195*) when I was moving, even when I was just poking around at 5 mph or when I was standing still at an idle. As soon as I go and work it such as climbing in the rocks, the temp goes to 240*. It would cool down as soon as I got moving again. I run a FI 258 w/ 4.0 head, 3 core radiator, high flow thermostat housing, 50/50 mix and a 6 blade flex a lite fan which seems to pull good air even at idle. What else can I do to keep it cool when in a situation like this?
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post #2 of (permalink) Old 12-30-2002, 10:52 AM
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Re: Over heating solutions?

typical solutions are running it with no thermostat, running mostly water. i have a 258 with the same fan you are running, and it never warms up.

i dont know if the 4.0 head has different cooling characteristics from the stock head, but i am looking into doing that head swap in the next 6 mos so would like to know if this is the case... [img]images/graemlins/givemebeer.gif[/img]
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post #3 of (permalink) Old 12-30-2002, 10:53 AM
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Re: Over heating solutions?

ps i think i may have seen a high flow water pump for the 258. definitely check into that also.
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post #4 of (permalink) Old 12-30-2002, 11:01 AM
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Re: Over heating solutions?

Thermostat/clutch fan with a good sealing shroud. Dump the flex fan.
post #5 of (permalink) Old 12-30-2002, 11:56 AM
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Re: Over heating solutions?

I second the clutch fan/shroud solution. When I put a 360 in my jeep I went with the stock heavy duty 3 core radiator with high flow thermostate and waterpump. I didnt' get a shroud (had one on the 6 but wouldn't work on the 8). I had trouble overheating at high RPM. I looked into it and found out that the clutch fan maxes our at 1800 RPM no matter how hot the engine gets. So I put a flex fan on. It was better at high RPM, but worse at low RPM. Still overall it was better, but not good enough. Then I spend the bucks and got a shroud. I had resisted because I thought the shroud was more for lower RPM.

The shroud made the biggest difference and the jeep ran passable cool on the freeway.

Recently, the flex fan broke and destroyed the radiator. Now I have an aluminim cross flow radiator, the stock fan, and no shroud (my new V8 shroud won't work with the new radiator) and the jeep still runs cool.

Sorry for the long answer to your short question.

I guess another option if you don't want to get a shroud is to install electric fans.

Good Luck

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post #6 of (permalink) Old 12-30-2002, 12:26 PM
 
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Re: Over heating solutions?

I recently had an overheating problem in my CJ after installing a 30 in it. This is what I ended up with. 3 core radiator, flex fan, good sealing fan shroud, high flow water pump, 165* thermostat. I run about 165-170 when moving (yes it does run good that cool), it might get to about 195-200 if I am running it real hard on the trail. I am not a rock crawler so I have not tested it that situation. I would first get the fan shroud. This is will make the biggest difference in cooling. A high flow water pump will only help if the rest of your cooling system is doing its job. Running it without a thermostat is not a good idea. For the radiator to cool the water/anti-freeze properly the coolant must stay in the radiator for a certain amount of time but not too long. No thermostat and the water will be going through the radiator too fast to cool it down. This has been hotly debated for many decades. I have personally found that this holds true. You live in a very cold climate, if I am not mistaken. Running no thermostat would cause very long warm ups and also makes running mostly water not a great idea. If the temperature does not get down to freezing you would ok in doing this. Also keep in mind that the more water you add the more chance of corrosion, however water is a better heat transfer agent. You have a give and take. If you go with a high flow water pump make sure you replace both upper and lower radiator hoses with the new ones with the inner spring core. The high flow water pump will cause the hoses to collapse if they do not have the spring inside. After I put a Flow Kooler water pump on my 360 I was still running hot. I replaced the hoses with the ones with springs and them and it reduced the operating temp, not by much but enough to make a difference. My flex fan pulls more than enough air to keep my rig cool. I was told by a reputable radiator shop that if the fan at idle will hold a rag to the grill solidly than the fan is pulling enough air.

To summarize:
1. Put on a good sealing fan shroud. Not just a ring around the fan in the middle of the radiator. The shroud must enclose entire core of the radiator and then circle around the fan blades.
2. Try a lower temp thermostat
3. High flow water pump and new radiator hoses
4. Replace flex fan with clutch fan – keep in mind that the different fans are likely to have different distances between the radiator and the fan blades when making your fan shroud.

Good luck and hope this helps out some.

[img]images/graemlins/givemebeer.gif[/img] and i can come up with all sorts of solutions, they just may not be the best! [img]images/graemlins/grin.gif[/img]
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post #7 of (permalink) Old 12-30-2002, 12:28 PM
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Re: Over heating solutions?

i stay away from clutch fans in general after watching roomate spend $400 replacing radiator, serp belt, shroud, etc after his yj's fan clutch gave up. i went to an electric fan for awhile to decrasee hp loss of using fixed fan, but got it wet a few times and it gave up.

i subscribe to the KISS theory (keep it simple, stupid) and run a fixed fan now. the less parts to break, the better.

is it common for flex fans to break? ive never encountered this and run them on both vehicles. [img]images/graemlins/givemebeer.gif[/img]
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post #8 of (permalink) Old 12-30-2002, 01:55 PM Thread Starter
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Re: Over heating solutions?

I forgot to mention that I do have a shroud on it. Its the orriginal 258 shroud modifided at the bottom to allow for the body lift. It doesn't fit tight up against the radiator, probably has a 5/16" gap between the radiator and the shroud. Also I am running a 195* Thermostat. Now correct me if I am wrong, but once the water gets above 195* (ie 210*) the thermostat stays open and water isn't allowed to sit in the radiator.
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post #9 of (permalink) Old 12-30-2002, 07:18 PM
 
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Re: Over heating solutions?

That is correct, once the thermostat opens water does not sit in the radiator. I have always beleived that as a motor gets warmer, the easier it is for it to keep getting warmer. If you lower the thermostat to like a 165 or 180 then you will have a better chance of keeping the motor cooler, provided you have a good cooling system in place. A thermostat temp change will not keep a motor that is overheating from overheating. Did you burp the system or air? make sure you have no trapped air in the system. 5/16' of an inch between the shroud and radiator should be fine, as long as the shroud completely surrounds the fan.
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post #10 of (permalink) Old 12-31-2002, 10:17 AM
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Re: Over heating solutions?

</font><blockquote><font class="small">In reply to:</font><hr />
is it common for flex fans to break? ive never encountered this and run them on both

[/ QUOTE ]

Yes, especially when you hit deep water, and there goes your radiator. Your're the first one I ever heard say a clutch fan came apart, when they go bad they just spin freely. Flex fan catastrophic failure is common, clutch fan catastrophic failure is not.
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