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Overheating solved

Hi NXJ4CB,

Your "Also, I read the temps at the radiator tanks and they are uneven" - can you give a little more description of what this means? Where on tanks? Are these the side tanks that run vertically when radiator is in vehicle? Horizontal tank at the top? Bottom? How uneven? How do you read temperature at spots on these tanks? Interesting to explore heat distribution within the radiator.

Thanks!


The measurements i read were, 160's at the top and bottom third of the tanks and the middle third roughly engine temps 200's. This was measured with an infrared thermometer going up and down the side tanks through the grill and not measuring the tube at all due to the condenser being in front of it. Discussions with smarter people tell me that the part of my radiator that is actually is the middle. The two thirds that aren't working are the stagnating cool areas.


I'm regretting the title of this thread. Definitely NOT solved! Yet! I've seen so many threads with no consensus on the solution. I was so happy when my temps went to normal I thought I have to spread the word...
Even if I haven't saved the world. At least this thread is out there and you gents are considering another angle I haven't seen in a forum yet.
I apologize for the misleading title. SOLVED is a big claim.


Thanks,
NXJ4CB
 
Quoting Patrick here: "Many years ago, I had one of those 3 core radiators. My XJ ran hot with it. A scan revealed the radiator had different temperatures in unexplained places. I kept it 2 weeks then tossed it,...TWO weeks brand new."


I'm really wondering if this "common" combination of High flow pumps, high flow housings and 3 row radiator will just never work.
How do you define running hot?
Am I wrong thinking that any movement of the needle is abnormal? When my jeep was "new to me" and stock, I towed all my posessions from San Diego to Tuscon and back again and the needle never budged (June). It always stayed just shy of 210. I own this rig because I overheated my Toyota pickup and had to junk it.

Now the needle is all over the place, it doesn't boil over but getting above 215 I believe is NOT GOOD. The highest temp I recorded is 234.



NXJ4CB
 
I don't think the needle should be all over the place, at least not in an XJ. My '95 Cummins is another story. But it is another animal.
 
Over heat for me is when the needle get close to the red. Half way between 210 and the red line is cause for concern even when I am pushing it hard up hill.
My XJ usually do not go pass the 210 mark except when sitting in traffic in South FL. before I added an AW4 cooler. I have since change the temperature at which the fans come on and added a cooler to the AW4.

Keep in mind my XJ do not have a mechanical fan for 12 years.
 
On thing to keep in mind is the temperature needle on the dash is not very reliable. It'll stick at around 210 even when the Jeep is actually in the 220-230 range and then suddenly peg hot around 240. I think this was done to prevent the average Joe from panicking over the jeep warming up a bit but let them know when there really is a problem. You need to hook up an OBD reader if you want to see the true temp.

From a fluid dynamics perspective I don't think your theory makes sense. The high flow coolant pumps increase output pressure which in turn will increase flow rate through whatever restriction are downstream. Right that restriction is split between the heater and the radiator. It's a misconception that the high flow pump can force "too much" coolant through the heater and "not enough" through the radiator. Increasing the fluid pressure will increase the flow rate through both restrictions at least a little bit. It's possible if the heater is wide open and the radiator is highly restrictive (seems like that would be poor auto design) that the majority of the increase in pressure is going to the heater, but there will always be at least a marginal increase in flow though the radiator due to the increased pressure over stock.

No matter what (stock or modded cooling system), increasing the restriction to the heater core will increase the flow through the radiator. I'm not saying this is a solution we should all implement. But if you have a problem somewhere else in the system and are overheating then cutting the flow to the heater will be a band-aid fix to increase the flow to the radiator.

I guess, I'm not buying your jump to saying that high flow parts are forcing "too much" fluid through the heater. High flow/pressure will increase the flow to everything, including the heater and the radiator.
 
While flow could increase with Rpm's, the pressure is constant based on the system cap. What can be reduced is the cavitation in the system. When the t-stat is closed the water has no place to flow and the pump is still trying to "put-out" causing cavitation. In the case of companies claiming higher flow rates, what is that based on?
 
While flow could increase with Rpm's, the pressure is constant based on the system cap. What can be reduced is the cavitation in the system. When the t-stat is closed the water has no place to flow and the pump is still trying to "put-out" causing cavitation. In the case of companies claiming higher flow rates, what is that based on?

Well there is a pressure differential in the system across the pump which causes the flow of coolant.

I see what you are saying but shouldn't the thermostat be open if you are having overheating problems? I can see this causing the jeep to heat up faster but with a properly operating cooling system once at operating temp the thermostat should open to control the temp.
 
Yes there would obviously be some pressure differential across the pump, but it can't be much. I think that would be the proper way to test pumps.
 
Having a similar issue with a 2 core champion radiator,high flow pump,180 tstat ,highflow water housing but it seems like the radiator will “heat soak” after about 30-45 min in the city with ac on in 90 degree temps,If you don’t don’t use the ac, she will stay under/around 210 during a 150 mile drive.
 
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