Running hot

Run down of what I have. Good running order no issues and used to run a solid 210 under all conditions. Older csf 3 core rad(proper mix using distilled water with a flush last year), hesco high flow thermostat housing, external trans cooler mounted in front of rad and mech fan, napa reman water pump, mopar rad cap and thermostat, confirmed working efan, napa wj hd fan clutch(i think its wj hd whatever the popular upgrade is and it seems to act fine, hard to spin cold spins more free when hot no leaks) confirmed temps with external sources, compression test shows all cylinders around 130+, no oddities on spark plugs(was thinking head gasket so I checked there), no coolant lose or signs of oil in coolant.

My temps have been all over the place lately. Driving stop and go traffic no ac they climb pretty quick and will cool down when I move. 215-220 but drops back to 210 when moving enough). Stop and go with ac the climb is more dramatic and never fully cools. 215-230 but never really drops much below 218 and and the longer the drive the higher it climbs and stays.

Ambient temps have an effect, at night when under 95 I can drive with ac full blast and sit right at 210 all night long it seemed in stop and go traffic. Freeway was a different issue and temps held at 215-218. When it gets close to 100 or over 105 and the problem amplifies Fast. Driving no ac on the freeway in 105 temps held close to 220 and would jump up if I got on the gas to pass but cool back down pretty quick to 220.

Using 2 different temp guns I confirmed the temps. I thought it was odd but may be totally normal that the driver side of the thermostat housing(small flat spot by the sensor) was showing the hottest. The passenger side(round part) was always showing pretty much 210.

I had a hesco high flow pump for years but it started leaking maybe 6 months ago and I replaced it with a napa reman. I didn't think a bad pump would present these problems or the hesco would have solved these issues since it fluctuates so much.

I was thinking not the fan clutch because its an issue in stop and to as well as freeway speed. Not temp sensor because IR temp guns confirmed. Not water pump because it does run cool at lower ambient temps.

Could be radiator plugged since it is getting up there in age and only gets hot under extreme conditions. Could be thermostat sticking, the temps on the housing seemed odd to me but again could be normal. Partial blown headgasket lettint exhaust into the cooling system.

My plan was replace the radiator since it is old, thermonstat while its drained and new cap just because its cheap. Any thing else to suggest before I throw money at the problem?

What was the last thing you did before you noticed the temp rise?

Have you burped the cooling system.

Fixed my ac and started using it. When I worked on the ac I didnt touch the cooling system at all. Last thing I did was the water pump months ago. Also the temps here i az have been really high lately.

Havent burped it but could do that for sure and see.

last month faced similar issues with my 96. Radiator was original 20 year old heavy duty 1 1/2 thick two core plastic tanks and alum core. Core was partially plugged with small leak. I found a perfect Mopar original Genuine Chrysler (52080104AC) Engine Cooling Radiator on Amazon $304 with ground UPS. It arrived in three days. While I was in there I replaced the pump with an identical AZone NEW one and ordered Gates belt and hoses, Stant 180 thermostat and cap. The replacement radiator was indeed original Mopar still in Mopar box. Perfect fit exactly like my 20 year old one except improved petcock. I live in Phoenix where outside temps in 115 range are common and in traffic temps considerably higher. The 180 thermostat helps engine run cooler except in extreme temps with AC on when it gets just above 210 and the pressure goes up. I have always run distilled water and coolant and changed it every couple of years. I was last into this system two years ago when I replaced the AC compressor, removed and flushed everything. I flushed the coolant system before replacing the radiator with Oxalic acid ( wood bleach ) followed by Prestone flush. Each flush done with distilled water and left in Jeep for a couple of days. Final complete drain except block then four gallon flush with distilled water before assembling the new parts. I went with another new AZone pump again because the last one I put in six years ago was still in great shape impeller included. I replaced it because I want another six plus years. I went with the 180 thermostat because my engine skips and cuts out when it gets hot so the longer I keep it below 200 the better it runs. One of these years I will find out what causes this cut-out but at this point it is probably a wiring problem. The new heavy duty radiator runs cool and trouble free even this past week when we hit 116.

How's the fan shroud? Sounds like a air flow issue, if it cools when you start moving I'm wondering if the mechanical fan is faulty, the hotter the temp the more the fan is suppose to lock up, not be easy to spin.

Another possibility is exhaust leak or plugged cat although you can usually notice those.

"napa reman water pump, napa wj hd fan clutch hard to spin cold spins more free when hot no leaks) "

Unless you typed that backwards the fan clutch is toast which fits the symptoms

Tip #2, never, ever use a rebuilt water pump. I use nothing but new Bosch water pumps on my Renix rigs now.

Rebuilt pumps and AZ pumps are like a box of chocolates, never know what your gonna get.

Fanshroud is stock and not cracked anywhere. I was thinking plugged cat but figured I would get some other symptoms. No exhaust leaks that I can see or smell, banks torque tubes have no sign of a crack.

I think Ecomike may be onto it with the fan clutch. Driving to work today it was 91 and my temps got down to 208 through a long stretch lf construction 25 mph zone. I noticed on my ultragauge that my engine load seemed to be fluctuating too.

I'll double check the fan clutch today, I've been checking so many things i may be spacing on how the fan clutch was reacting. I'll check it hot or cold and plan to warranty one this weekend.

When my hesco pump died I needed something quick and cheap. Another hesco is on my list and then keep the napa pump as a backup. I was thinking of trying to rebuild the hesco pump, all the money is for that cool impeller really.

Fan clutch info:
Replaced 8-19-13(under warranty) ZJ fan clutch NAPA 272310

If that things not roaring when you first start it and then again when it gets warm, it's bad.

Got home and gave the fan clutch a spin, While hot, engine off and getting as much of a spin with the limite space I can. Spun it about 1 fan blade diststance or about 1/6 rotation. Ill wait until its full cool and spin the fan again. Also while the engine was running I reved it under the hood and the fan speed increased alot. Not sure at idle if its spinning as fast as it should, everything is loud its hard to tell but I remember when I first put that Zj clutch in it was a beast.

I noticed my temp when i pulled in the garage was 215 and the time it took me to pop the hood, get out and rev the engine under the hood the temp jumped to 225 that quick in maybe 1 minute idling and 2 quick throttle blips.

Cold fan spin felt about the same maybe very slight less resistance than when warm.

I think you need a fan clutch.

I'm going to try and swap out the fan clutch today. Still seems odd to me that it would run hot on the freway. I thought at freeway speeds the fan was no match for the airflow just from the speed n

iwannadie said:

I'm going to try and swap out the fan clutch today. Still seems odd to me that it would run hot on the freway. I thought at freeway speeds the fan was no match for the airflow just from the speed n

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You're correct.

What thermostat are you using?

The only ones I've found that heat your vehicle quickly, and keep them at a stable operating temp is the factory one.

Oem mopar tstat.

Could a bad fan clutch cause drag and restrict air flow at freway speeds or just increase engine load enough to over heat.

iwannadie said:

Could a bad fan clutch cause drag and restrict air flow at freway speeds or just increase engine load enough to over heat.

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Doubtful.

cruiser54 said:

I think you need a fan clutch.

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I agree!!!

iwannadie said:

Could a bad fan clutch cause drag and restrict air flow at freway speeds or just increase engine load enough to over heat.

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I have had a bad fan clutch on my old Dodge charger go bad an over heat at freeway speeds and even more at idle. I switched to a flex fan back in 1978 as the clutches back then were too weak for lean burn 400, 4 barrel beast.

I have little trouble with today's clutches. I always test new ones before I install then with boiling water in a frying pan. They should nearly lock up to direct drive at 200F (boiling water in a pan is 212 F) and be almost impossible to spin. At room temp they should turn pretty freely, but with resistance compared to 200 F.