Jeep Cooling Basics

[bonza]

what the TJ's and presumably the XJ's need is a larger volume radiator that holds more coolant and a fan that blows more cub meters of air

to remove heat requires a certain volume coolant and flow rate and a certain volume air flow over the radiator fins that is proportional to ambient air temperatures.

hotter the ambient air then more air is required to pass over the fins and a greater volume of coolant is required to be exposed to the cooling air currents.

the existing vehicles are border line in design, so every rad tube has to be clear etc etc. there is simply very little room for error

the TJ certainly has room for a deeper radiator that would accept at least a 40% increase in volume. this would not adversely affect performance by lowering temperatures too much in winter as the thermostat will ensure minimum temperatures are held at the stat set point of 195 F

[kj69]

Originally Posted by Steve F

I've always wondered why so many have so many cooling issues. My 2000 XJ towed my camper up the bells line of road over Australia day last year when we were hitting 45c. The camper weighs about 550KG loaded and the XJ is on 3.55's with 32x11.5x15. This is pretty much the worst condition my XJ has seen, on top of that it had a leaking radiator (replaced when I got back with an Adrad). I had no overheating issues, sure it got warm but nowhere near the 'red'.

I've since replaced the radiator and as preventative maintenance replaced the hoses. Other than that the rest of the cooling system is stock with 140000km on it. Is the cooling system really that bad or does it just come down to poor repair?

As an aside I'm about to put in 4.56 ratios which should reduce the load on the engine significantly.

Should also add I've had the XJ for 8 years and have put 120000 of those KM's on it with trips up to Port Douglas in Summer included in there etc.

Cheers
Steve

x2 even wheeling with thermo fan out of action no overheating

[carvesdodo]

Originally Posted by Jeepology

Weirdly my VE SS (2010 6L) runs at between 103 and 108c with just mild driving....

Not that weird ... its all part of that "global car" nonesense that got started in the 80's .... and the change from water to coolant.

The later model stuff is also better suited to the higher temps because of the changes in materials used in manufacture .... but still - one would hope that an "aussie" car at least has a better functioning cooling system than the imports to maintain these "designed" temps ... altho I think Auberon summed it up ....

Originally Posted by Auberon

It revolves in its simplest form around some key words: Enthalpy, entropy and the laws of thermodynamics and ambient conditions.

The first 3 are consistent worldwide but the latter is the most significant of variables as you note and significantly NEGLECTED or minimised in design.

Originally Posted by Steve F

I've always wondered why so many have so many cooling issues. My 2000 XJ towed my camper up the bells line of road over Australia day last year when we were hitting 45c. The camper weighs about 550KG loaded and the XJ is on 3.55's with 32x11.5x15. This is pretty much the worst condition my XJ has seen, on top of that it had a leaking radiator (replaced when I got back with an Adrad). I had no overheating issues, sure it got warm but nowhere near the 'red'.

I've since replaced the radiator and as preventative maintenance replaced the hoses. Other than that the rest of the cooling system is stock with 140000km on it. Is the cooling system really that bad or does it just come down to poor repair?

As an aside I'm about to put in 4.56 ratios which should reduce the load on the engine significantly.

Should also add I've had the XJ for 8 years and have put 120000 of those KM's on it with trips up to Port Douglas in Summer included in there etc.

Cheers
Steve

Originally Posted by kj69

x2 even wheeling with thermo fan out of action no overheating

X 3 .... Altho I regard overheating as any temp more than fifteen degrees over the thermostat setting. If the cooling system cant keep the eng temp to somewhere around whats stamped on the thermostat - something aint right

Sheesh ... sydney must have been hot for Bell Line of Road to be those temps Steve F

Hmmmm ... just looking at the pic below ... what are we doing differently to ensure that spiking temps from the inadequate factory cooling system dont happen then ???

Perhaps a bit of airflow out the rear corners of lifted bonnets ? / better radiators ? / snorkles ? / extractors ? / better maintenance & vehicle knowledge ? / better driving styles ? / the correct mix of green stuff ? / electric fan control ? / better operating thermostats compared to the factory ones ... maybe even faulty factory thermostats that opened as soon as normal thermostats ?

Tis an interesting little conundrum.

[Doctor W]

As an oblique addition to this very excellent threading may I just add that Mackay Rubber makes a range of radiator and heater hoses that are positively cheap compared to the usual suppliers ......available by ordering from Supercheap after paying a $16 "special order" charge or porbably most other parts places.....prices? e.g. $15 and $23 for the heater hoses and about $ 29 and $35 for the top and bottom hoses on a ZJ 4.0.........worth knowing about.

Perhaps we could could do a "sticky" thread......... with info on where to get "alternative" parts/etc , commonly interchanged generics etc......a ueful resource page I'd think!

[bruggz351]

Originally Posted by Doctor W

As an oblique addition to this very excellent threading may I just add that Mackay Rubber makes a range of radiator and heater hoses that are positively cheap compared to the usual suppliers ......available by ordering from Supercheap after paying a $16 "special order" charge or porbably most other parts places.....prices? e.g. $15 and $23 for the heater hoses and about $ 29 and $35 for the top and bottom hoses on a ZJ 4.0.........worth knowing about.

Perhaps we could could do a "sticky" thread......... with info on where to get "alternative" parts/etc , commonly interchanged generics etc......a ueful resource page I'd think!

X2... Top idea

[bonza]

Originally Posted by Doctor W

Perhaps we could could do a "sticky" thread......... with info on where to get "alternative" parts/etc , commonly interchanged generics etc......a ueful resource page I'd think!

x 3. fab idea. would need contributions from members

I access a motorcycle forum and they have an alternative parts sticky. very useful

[carvesdodo]

Something for 2000 / 2001 XJ Cherokee owners.

Apparently there is a dealer flash of the computer available - to change the computer temp settings that the aux fan operates at.

i.e. The fan will activate sooner.

Probably part of the heat soak issue which also requires insulating the injectors or something on that model.

Advice from my local dealer is that it wont be applicable to vehicles earlier than those year models, as it may cause computer issues in vehicles not having the relevant VIN.

For those with 2000 / 2001 year models ... just give your VIN to the dealer and ask whether the aux fan computer reset TSB has been done.

----------->http://www.naxja.org/forum/showpost....2&postcount=39
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