High Flow Thermostats

At idle, or normal city driving, there is no way the water will move too fast. The performance of centrifugal water pumps falls off tremendously as rpm is lowered.

Multi-row radiator could be a drawback not a benefit if the fan isn't up to the task. There is more air restriction. As I said before about this Jeep, if your driving is city and off road, big noisy fan is where it's at.
 
Updating to a later year electric fan has the advantage of allowing full speed cooling at low RPM's. You could also consider adding an auxiliary electric pusher cooing fan in front of the AC condenser. I think some Cherokees came with this as a stock option.
 
Originally Posted by ripcord
Does the temp go down if you get on the highway and cruise for a while?

Yes about 210-215 on the freeway
 
210-215 is what the car is designed to run at so that's normal.

How about bugs and crud in the radiator fins? Maybe try spraying the radiator and condenser down with simple green and then spray it off with the garden hose from inside the engine bay pointing towards the front.
 
Originally Posted by Nick1994
Originally Posted by dlundblad
I'd personally look more into a multi row radiator.

Yes I've posted to CherokeeForum for suggestions, will get something good.


Hopefully other Jeep owners will give you some good ideas.

I just looked on Rockauto, and they list several one and two-row radiators that measure 1 1/4 inch thick and a three-row that is 1 11/16 thick. I wonder if the extra 7/16 would increase cooling capacity significantly. Then there's the question of getting a quality part--I know nothing about the brands listed.
 
Generally speaking, overheating around town, at stoplights, etc vs at freeway speeds indicates insufficient air flow across the radiator.
Via the radiator, aka heat exchanger, heat moves to cool until it achieves ambient temperatures.
Ya gotta move sufficient air.

Of course, this assumes all components are in good operating order.
Our '65 4-4-2 came with a steel X fan; no clutch, no shroud.
I bought an AC (6 or 7 blade maybe) and a fan clutch. This fixed the heating issues in this heavy car with a 400 cu in iron headded V8.

You will hear people say slower coolant speeds will remove more heat from the coolant because it is in the radiator longer.
Hogwarsh. There is a fixed volume of fluid in the system.
If you move it twice as fast, a given amount is in the radiator 1/2 as long but twice as often.
Coolant heat will continue to be exchanged to the air until it reaches ambient temperatures.
Average temperature will be lowered.

Good luck.
 
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Originally Posted by SpitFire6
The faster the flow the better the cooling.
The maximum flow will be before the pump cavitates.
"less time in the radiator to cool down" is a fallacy.

Edit: PS. I am ignoring laminar/turbulent flow considerations.


Slower flow rates will absorb more heat.

I'd personally look more into a multi row radiator.

Hi, I am not sure if you agreeing with my statement "The faster the flow the better the cooling."?
Cheers,
Iain.
 
Just the opposite. Slower flow would cause better cooling (heat absorption).
Sounds like you are suggesting a slower water pump & lower airflow will increase cooling? If so, that's plain wrong.
Faster water coolant flow & faster airflow will increase cooling on a vehicle.
I will leave it for somebody else to explain your error & I hope you understand.
 
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I’ve ordered a Flowkooler high flow water pump and a Hesco high flow thermostat housing. Will install a 195* high flow thermostat and see how it performs.
 
Sounds like you are suggesting a slower water pump & lower airflow will increase cooling? If so, that's plain wrong.
Faster water coolant flow & faster airflow will increase cooling on a vehicle.
I will leave it for somebody else to explain your error & I hope you understand.

Well, both of you are only conditionally correct and that condition depends on where that velocity, volume and density ( of both the coolant and air) are relative to the amount of heat to be removed and total area of exchange.

Many people think this is a simple linear equation but that's not even close.

Given the coolant properties ( viscosity, Sg, chemistry, system volume, additives etc.) and the amount of energy (heat to be removed) there is a necessary soak time for the transfer (fluid dwell) and there is always an upper thermal transfer limit before changes of state start.

Optimum velocity is calculated between those 2 for the amount of heat to be removed. It can be too fast or too slow.

On the air side, ideally you want dense cool air on the front absorbing heat and increasing velocity on the exit side.

But as with the coolant, there's a point where velocity will create dead air pockets over fins and tubes which will act as insulators like an airfoil. That velocity negative transfer effect can be worsened if air cannot evacuate faster than the feed, if the forcing cone doesn't cover the entire transferring surface ( shroud issues) or if there is a significant approach angle issue.

There's just a lot more to successful heat removal than just buying a big tank and a fast pump.
 
Spot on, there is a ;ot more to it than that. Even the highest flowing thermostat is restrictive, higher flow is beneficial when you get into multi core radiators. Tuning restrictors are sold in various sizes for this very reason.
Turbulance, cavitation, hot spots, how the coolant flows through the engine all have to be taken into consideration when modifying the system.
 
Spot on, there is a ;ot more to it than that. Even the highest flowing thermostat is restrictive, higher flow is beneficial when you get into multi core radiators. Tuning restrictors are sold in various sizes for this very reason.
Turbulance, cavitation, hot spots, how the coolant flows through the engine all have to be taken into consideration when modifying the system.

Don't even mention "nucleate" reactions in systems not designed for it
 
I have read a few papers on nucleate boiling, interesting stuff but you would know more about it than me, I am just an old time wrench turner.
 
I think the posts were talking about radiator dwell time. Dwell time is not affected by coolant speed in a closed loop system.
Certainly other component limits come into play as well. A matched system is best.
That's why I say everything else being equal and in good working order, etc.
So everyone is right... All good.
 
I have read a few papers on nucleate boiling, interesting stuff but you would know more about it than me, I am just an old time wrench turner.
You are considered a whole lot more than "just an old time wrench turner" around here.
You remind me of my old friend Lars Grimsrud. 'Cept he's meaner.
 
Hi,
The thermostats flow restriction causes a higher coolant pressure in the head raising the boiling point at high RPM & load.
One reason a car overheats with no thermostat/restriction.
Cheers,
Iain.
 
Well, some of the test results are in. I've installed a Flowkooler high flow water pump, a Hesco high flow thermostat housing, and a new high flow 195* thermostat. Also used coil cleaner on the A/C condenser coils (I've hosed them out before).
Temperature results below are checked with a scan tool.

It's only 105 out right now so I'll have to test again when it's hotter, but I've got some major improvements. 210 degrees at idle with the A/C on (Was creeping around 230 before). I turned the A/C off (which also turned the electric fan off) and it creeped to 218 which is where the electric fan kicks on, and it cooled easily to 215 and the fan kicked off. I left the A/C off and turned on my manual toggle switch for the electric fan and it got down to 203!
Very happy with these results so far.

Here's some pics of cleaning the coils. I used some snow sleds to catch the drippings. Quite brown but it also could be some dirt from the radiator cradle too.
 

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