COOLING PROBLEM(little long)

:banghead: :confused1

1996 cherokee inline 6 with aw-4 automatic.

vehicle running at 235F measured on the head.

both myself and then a shop did the following: replaced all the hoses, thermostat, thermo housing, water pump, radiator, chemical flush, block pressure check, head pressure check, computer diagnosis, sensor check and replacement, electric fan instead of mechanical, another fan (large shop type) to assist radiator cooling, replaced all relevent fluids, all with NO DECREASE in temperature.

anyone got any ideas?

I live in orange county, california, any shop you might suggest?

put your mechanical fan back on. I personally never had any luck with an electric fan in replace of the mech. Also i just put hood vents in and it HELPED ALOT, at least 15 degrees cooler under the hood, runs about 215 with the a/c on a 100 degree day.

since we were measuring the temp with the hood open the hood vents would only help slightly if at all.
electric fan was the first step since it is mostly a trail rig. mechanical fan going back on is probable.

anaheimxj said:

electric fan was the first step since it is mostly a trail rig. mechanical fan going back on is probable.

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You backed into a larger problem on your first step, no CFM to provide adequate heat rejection. The factory mechanical fan shroud, fan, and fan clutch will beat the electrics anyday. Reinstall the factory mechanical pieces and retest.

Since you reawakened the cooling thread ...

Has anyone found a replacement mechanical fan with deeper pitch blades to move more air at higher static pressure? Something besides the factory fan? While the factory fan is good has anyone found (or built) a better mechanical fan replacement?

still don't think it will help. the problem existed prior to electric fan. also addition of more cooling by shop fan didn't help, why would the mechanical fan be the "fix"?

Rod out the radiator

I would rod out the radiator. I had a new Modine and apparently it was plugged up quite a bit during assemly. Went through all the heart ache you are going through and finally was recomended to try that. IT WORKED! Hope this helps.

anaheim --

How did you measure the 235 degrees at the head? Was this using the OEM sender and OEM gauge on the dashboard? If so, first try a different sending unit (be sure to get the one for gauges, not the one for idiot lights), or better yet check it with a known-good mechanical gauge.

The factory instrumentation is not 100% accurate. I regard it not as an accurate indicator of anything absolute, but rather a visual display of status. After 15 years and 238,000 miles, I sort of know where the needles usually point, so if they point anywhere else I try to find out why.

it was measured with a non contact thermometer.
the dash gauge is off by about 10 degrees cooler than actual.

I put in a gdi 2-core first, it did not help.
the shop had it tested and cleaned, still no change.

anaheimxj said:

it was measured with a non contact thermometer.
the dash gauge is off by about 10 degrees cooler than actual.

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Okay, then I'd want to know where the reading was taken, and whether or not you have taken readings at the same location on a few other XJs to establish a baseline for demonstrating that your reading is abnormal.

The rear corner of the head is a hot spot. The fact your reading differs from the factory gauge likely doesn't indicate a problem -- the gauge sender is immersed in the coolant stream. Coolant circulates to remove heat from the engine. Heat cannot be transferred unless the metal is hotter than the liquid circulating through it. If they are the same temperature there is not transfer, if the liquid is hotter then it heats up the metal.

To be honest, from what you have described so far it sounds like your engine is operating normally and you're chasing a non-existent problem.

the front of the head got hot quicker than the back.
then it evened out.
the readings were taken all across the head.
to me 235 is too hot.

anaheimxj said:

still don't think it will help. the problem existed prior to electric fan. also addition of more cooling by shop fan didn't help, why would the mechanical fan be the "fix"?

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The mechanical fan was removed and replaced, with the electric fan (with no improvement in cooling performance), before your other improvements were made, so none of your testing included the mechanical fan. What do you have to lose by reinstalling the mechanical fan?

Airflow is proportional to the horsepower available to drive the fan. More airflow demands more power, as governed by the physics of fan laws. Doubling the airflow from a fan requires doubling the fan rpm and the cube of horsepower (if 1200 cfm = 600 rpm @ 5 hp, 2400 cfm requires 1200rpm @ 125 hp). You can swap the fan to a more efficient model and find the hp for given airflow will be lower, but doubling airflow will still remain the same cube power requirement.

Electric fans are designed to be power limited to prevent overamp current draw and burning wires (10A at 12vdc is only 1/6 hp). The mechanical fan has no such limitaton (other than a 50 hp + capacity drive belt). The mechanical fan and a tight fan clutch has the potential to move more air because it has more horsepower to drive the airflow (and the XJ fan uses the power with the clutch engaged, enough to drop a 1100 rpm fast idle speed 200 rpm).

As an experiment try turning the factory fan with an electric motor (a Moroso electric water pump drive or other systems) and see how well it spins the factory fan blade? I have done this and the result is not impressive (the rpm is very low for the current draw).

The box fan used in testing may move good cfm with no pressure loss, but try to channel the airflow through a radiator and the flow quickly suffers from the pressure drop. These box fans are not designed to provide the pressure needed to aid in airflow through a restrictive heat exchanger (they are also designed to be electric current draw limited).

Again, what do you have to lose by installing the mechanical fan, clutch, and shroud?

PS: I would have the radiator rodded out. You may also want to check the radiator construction: GDI makes a three row model nearly equal to the factory HD cooling Modine two row in heat transfer performance. You may need the three row or the HD Modine.

The radiator was rodded out.

I have no problem reinstalling the mechanical fan. I just felt that there is more to the problem than that, and so does the shop I took it to.

Is the Modine all aluminum or does it have plastic ends?
I read somewhere that the Modine has more cooling ability, 1" vs. 3/4" on the 3 row G.D.I.. However I am not comfortable with plastic.

My factory Modine has metal tanks.

You say factory. Where do I come up with one?
What do I tell the radiator place to get me a Modine?

I would hope an member would offer a discount Modine rep phone number (anyone)?

have no problem reinstalling the mechanical fan. I just felt that there is more to the problem than that, and so does the shop I took it to.

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first off I think I would get a second opiion from another shop...and second if the coolant temp is round 210 to 215 the surrounding metal shoudl be around 20* hotter...thats the way thermal dynamics work....I dont think you have a problem..just a shop trying to stay busy

anaheimxj said:

to me 235 is too hot.

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It may seem too hot to you, but if that's what all XJs run at then it isn't too hot. I see XJnation has chimed in to confirm my statement about the way thermal dynamics work. Heat always transfers in one direction -- from the hotter material to the colder. With the sender unit immersed in circulating coolant, if it is reading 210 (which is what most stock XJs show on the gauge when warmed up) it is virtually axiomatic that the surrounding metal is hotter than that.

I still think you don't have a problem but a normal condition. Before you drop 200 clams on a new radiator that may not make any difference, I think you should take similar measurements off a couple or more stock XJs to establish a baseline operating parameter.

JMHO -- it's your money.

I agree with you guys on the thermal dynamics theory.
I will get additional readings from other XJs.
I am a little hard headed at times, and just feel that the coolant flowing out the recovery bottle overflow, with the gauge showing 260 while sitting in the driveway and the hood open both fans running, might indicate another problem.

anaheimxj said:

I am a little hard headed at times, and just feel that the coolant flowing out the recovery bottle overflow, with the gauge showing 260 while sitting in the driveway and the hood open both fans running, might indicate another problem.

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You may have a point there. However, we who are trying to help you are being given conflicting information. It might have been helpful to post the complete information when asking your question. What you wrote to open this thread was:

vehicle running at 235F measured on the head.

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There's a big difference between 235 measured at the head, and 260 on the gauge with the system hemmoraging. That was not previously mentioned. At idle it should remain in the range of aux fan operation -- warming up enough to activate the aux fan, then cooling down enough to allow the aux fan to cycle off again.

How about starting from the beginning and explaining exactly what the initial symptoms were, what corrective actions were taken and in what sequence, and what (if any) effect any of those actions had.