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Discussion Starter · #1 ·
Hi all. I have 78 CJ7 with a recently rebuilt 360. At idle for over 5 mins, it will almost certainly overheat. I don’t think this is necessarily an issue with the 360 only, cause the 304 that came out did the same. I have a new aluminum radiator with 2 electric fans (always on with ignition). It will stay at a good temp with the hood open, but as soon as the hood goes down the temp starts climbing. Any ideas on keeping the temp down?

Thanks in advance.
 

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Fans blowing the correct direction? Lose the cool air to blow over the radiator once the hood closes.
 

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Discussion Starter · #3 ·
Good question. The fans are pulling air from external over the radiator into the engine bay.
 

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How hot is "overheating'"?

Are you using an electric gauge?
Double checked with a mechanical gauge?

Verified temp with an IR gun?
 

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HI, are you sure your cooling system is full? can you get us a picture of you fan and radiator set up? are the fan's pulling thru the whole radiator with a shourd ?
good luck take care be safe
tim
 

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Discussion Starter · #6 ·
The coolant level is ok. I have not verified temp with an IR, but the gauge is correct (speed hut gauges). It’s gets hot enough to overflow the radiator. I’ll post a pic asap.
 

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Would not be the first time hearing of a defective "new" thermostat....
 

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Ever notice people have overheating issues when they switch to electric fans….:laugh:
 

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The coolant level is ok. I have not verified temp with an IR, but the gauge is correct (speed hut gauges). It's gets hot enough to overflow the radiator. I'll post a pic asap.
Hot enough to overflow the radiator may be something as simple as a defective radiator cap.
What temps are we talking about?
 

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HI ... IN the picture in post #8... I see the problem. The top hose is above the radiator.. Its is causing a big air block.. looks like a foot or better .. the hose can't be above the radiator so it can flow properly..
good luck be safe take care
tim
 

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It does appear you are using the wrong upper hose. The correct hose stays lower than the radiator inlet.

Whether that's the cause of your overheating, I can't say.

I'd be suspect of those dinky fans, however. They sure don't service much of the surface area of the radiator, and without a shroud, they aren't cooling as well as they could.

Matt
 

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Hi all. I have 78 CJ7 with a recently rebuilt 360. At idle for over 5 mins, it will almost certainly overheat. I don’t think this is necessarily an issue with the 360 only, cause the 304 that came out did the same. I have a new aluminum radiator with 2 electric fans (always on with ignition). It will stay at a good temp with the hood open, but as soon as the hood goes down the temp starts climbing. Any ideas on keeping the temp down?

Thanks in advance.
It sounds like and air flow problem. I would use a 7 blade engine driven declutching fan with a shroud. That should flow a lot of air.. Is there any sheet metal work, etc., restricting air flow out of the engine compartment?
 

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The picture is a little deceiving. The bend in the hose is higher than the radiator inlet, but not by much. Maybe as high as the cap. Here’s another angle.
HI. any amount above the radiator is NOT GOOD it cause an air block.. When you fill the radiator with coolant you CAN NOT fill any portion of the hose that is above the radiator, when you fill the radiator you can only fill it in a level Horzional plane with the radiator, leaving a air block that well never fill.
Also those fan are way too small with a V8 especially with them Not pulling thru the whole radiator core.
good luck take care be safe
tim
 

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Good thing the coolant flows out the top hose as it has zero effect on cooling
 

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Thermostat opens and water flows into top of radiator. Engine off and cools off water can drain into top of radiator .leaving air in the upper hose. This can happen with a hose going down hill to top of engine also. Squeeze the upper hose on a cold engine and you can feel (and hear the coolant drain into the top tank of the radiator. That won't cause the air pocket that you worry about in the engine. Run the engine, coolant heats up, thermostat opens and pushes the air to the top tank of the radiator where it stays. Always has air in top tank of the radiator. Upper hose gets hot, you don't have a air pocket in it as coolant flows through (when engine is off, cools off, thermostat is closed, air won't flow from hose past the thermostat into engine. If you can drive 35mph or more and engine is cool it's a airflow problem (fans not large enough cfm, radiator partly blocked, thermostat not open enough). I have a cj8 with chevy 350 (330 hp) motor with a 16" flex lite electric fan, no shroud and 180 deg thermostat, fans come on at 190 deg, cools down to 175 deg. Fan comes on again at 190 deg. This is while sitting in shop idling. Also all aluminum radiators are not created the same when it comes to cooling.
 

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I never said anything about the level of coolant, if a person is of “diminished mental capacity“ and thinks less fluid=more cooling… I have some ocean front property in the desert you would be interested in….
 
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