TJ running too cold

[Mopud]

Morning folks,

I'm having a few issues getting the TJ up to operating temperature. Changed the thermostat from China crap to factory genuine and it certainly did help but not completely.

I've got my novak thermo activating at 96-97 degrees.. the fan controller is a Derale unit and will deactivate once it goes 3-4 degrees below the activation temp (so 92-93 it'll switch off).

With a 195f thermostat, technically it opens at 90-91 degrees. When is the best time to set the thermo fan to switch on? Most of the time the car runs so cool the thermo fan doesn't even get a chance to come on anyway.

On freeway runs it'll hit low 80s and idling it'll be lucky to crack 93-94 - only excessive idling and extreme heat will the fan actually switch on.

Cheers,
Mopud

[Dustbowl]

Mopud, those temps look awesome to me, nothing too cold about them :)

[Mopud]

Mopud, those temps look awesome to me, nothing too cold about them :)

Summer hasn't quite kicked yet either so i should be grateful for the low readings. But low 80s on freeway drives is ok?? Thought it might be a little too low? Thanks pal

[Dustbowl]

Summer hasn't quite kicked yet either so i should be grateful for the low readings. But low 80s on freeway drives is ok?? Thought it might be a little too low? Thanks pal

No not at all, I'f it were in the 60's there would be an issue, but those temps are a tribute to your excellent cooling system, I assume you must have gone for a triple+ core copper radiator and replaced the water pump, with your stroker, on top of a good thermo and excellent airflow, your motor loves you! :p

You will be greatfull on the next 40+ degree day :p

[Mopud]

Yes sir, Answer D, all of the above. I know optimum running temp for these engines is ~99c so I was of the logic that temps should be as close to that as possible.

It's been leaning out on the top end so I was thinking it could be temp related especially with the CEL coming on and off when running on the freeway; previously temps would drop to low-mid 70s - with the new tstat, temps are staying in the 80s so far though so I'll have to see if there's any change in that front but the issue is likely something else.

Thanks for the words of comfort, at least I know i'll be good for summer - I think it's the first time I've been able to say that in a good 5 years!

[Dustbowl]

Hahaha have you looked at replacing your temp sensor?
It can directly effect your fuel injection, idler control and ultimately stuff up your fuel air balance (too lean or too rich), this may also effect your overall answer.
I have heard of gauges reading right on the dash but telling the computer it's minus thirty!

[bonza]

Morning folks,

I'm having a few issues getting the TJ up to operating temperature. Changed the thermostat from China crap to factory genuine and it certainly did help but not completely.

I've got my novak thermo activating at 96-97 degrees.. the fan controller is a Derale unit and will deactivate once it goes 3-4 degrees below the activation temp (so 92-93 it'll switch off).

With a 195f thermostat, technically it opens at 90-91 degrees. When is the best time to set the thermo fan to switch on? Most of the time the car runs so cool the thermo fan doesn't even get a chance to come on anyway.

On freeway runs it'll hit low 80s and idling it'll be lucky to crack 93-94 - only excessive idling and extreme heat will the fan actually switch on.

Cheers,
Mopud
for a start your fan is cycling on correctly. it shouldn't come on if the temperature is below the thermostat setting. when the thermostat is closed there is just a pool of static water in the radiator that is not circulating thru the engine so having the fan running in that situation is useless

when the thermostat cracks open at 91C water begins to flow thru the radiator. if moving at speed the airflow passing thru the radiator should be enough to cool the water prior to it re-entering the engine block.

if the coolant temperature near the thermostat goes over about 95C it should be wide open allowing maximum coolant flow so that the radiator combined with with an airflow can then do its job. when it exceeds this temperature even more, the fan comes on to provide additional airflow thru the radiator and bring down the water temperature prior to it re-entering the engine block. the temperature sensor is located the thermostat housing to measure coolant temperature

a thermostat sets the lowest coolant temperature so if your engine is running at low 80'sC the stat should be shut closed, but there could and should be a trickle of coolant leaking pass the thermostat in the closed position, or perhaps your temperature readings are not that accurate

low to mid 80'C is nothing to worry about though, thats what my Jeep runs at during cooler days, rarely exceeding 95C on the hottest of days

as an aside Stant thermostats are about the best. they have a "jiggle" valve in the flange that always allow a small constant flow into the radiator and help with bleeding any air out of the system. some drill a 1/16" hole in the flange for the same reason. and yes, dont use Cina stats, your engine is worth more than the $2 you would save

[Mopud]

Hahaha have you looked at replacing your temp sensor?
It can directly effect your fuel injection, idler control and ultimately stuff up your fuel air balance (too lean or too rich), this may also effect your overall answer.
I have heard of gauges reading right on the dash but telling the computer it's minus thirty!

I have indeed but just not been bothered to source on! It's still the original from factory so it wouldn't hurt to change it at some stage I'm sure.

[Mopud]

for a start your fan is cycling on correctly. it shouldn't come on if the temperature is below the thermostat setting. when the thermostat is closed there is just a pool of static water in the radiator that is not circulating thru the engine so having the fan running in that situation is useless

when the thermostat cracks open at 91C water begins to flow thru the radiator. if moving at speed the airflow passing thru the radiator should be enough to cool the water prior to it re-entering the engine block.

if the coolant temperature near the thermostat goes over about 95C it should be wide open allowing maximum coolant flow so that the radiator combined with with an airflow can then do its job. when it exceeds this temperature even more, the fan comes on to provide additional airflow thru the radiator and bring down the water temperature prior to it re-entering the engine block. the temperature sensor is located the thermostat housing to measure coolant temperature

a thermostat sets the lowest coolant temperature so if your engine is running at low 80'sC the stat should be shut closed, but there could and should be a trickle of coolant leaking pass the thermostat in the closed position, or perhaps your temperature readings are not that accurate

low to mid 80'C is nothing to worry about though, thats what my Jeep runs at during cooler days, rarely exceeding 95C on the hottest of days

as an aside Stant thermostats are about the best. they have a "jiggle" valve in the flange that always allow a small constant flow into the radiator and help with bleeding any air out of the system. some drill a 1/16" hole in the flange for the same reason. and yes, dont use Cina stats, your engine is worth more than the $2 you would save

Roger that, bonza. Thanks for the detail. I'm just about to post a couple of pics of the temp probe placement to see what you all think. I'm of two minds about it.

[Mopud]

This pic shows the T-piece I installed to accommodate the temp probe for the Derale thermo fan switch. I've had mixed responses on the placement of this and how it can interfere with the 'coolant flow' to the temp sensors for the factory probe and the secondary one.
https://lh5.googleusercontent.com/-VuDh8_rCrwA/UM6fA-OhQ7I/AAAAAAAAAXg/NOYSfhq4xAI/s857/WP_000272.jpg


Here you can see the Derale thermo fan switch unit and just behind it, the location of the old probe I was using (grey wire running on top leading to the push-in radiator probe) when I had the Davies Craig fan controller running before it melted (it wasn't amp rated high enough to handle the Novak fan).
https://lh6.googleusercontent.com/-D_V98Px7ZXM/UM6e_7iiO3I/AAAAAAAAAXc/bIwYxPVM5G4/s857/WP_000273.jpg

Any opinion on using either of these probe types?

[Tassie Jeeper]

boy that is a snazzy cooling system:cool:

all u need now is a redarc coolant alarm

[bonza]

the OEM temp sensor originally would have its probe directly in the path of coolant flow located in the stat housing.
now that a Tee piece has been fitted coolant in the Tee is static that the probe is in contact with, not really flowing so it isnt ideal as it could be measuring a slightly lower temp

[carvesdodo]

the OEM temp sensor originally would have its probe directly in the path of coolant flow located in the stat housing.
now that a Tee piece has been fitted coolant in the Tee is static that the probe is in contact with, not really flowing so it isnt ideal as it could be measuring a slightly lower temp


.... X 2

Probably better to buy/make, a joiner to fit into the heater hose or rad hose for the fan controller.

[lifted TJ]

Why dont u just put it back to factory for a day and see if it makes a difference?

[Mopud]

Why dont u just put it back to factory for a day and see if it makes a difference?

Not quite sure how I'd go about doing this... I still need a temp sensor to activate my thermo fan.

[Mopud]

boy that is a snazzy cooling system:cool:

all u need now is a redarc coolant alarm

ha, i use an engine watchdog in the cabin http://enginewatchdog.com/ it has saved me on two occasions already!

[Mopud]

the OEM temp sensor originally would have its probe directly in the path of coolant flow located in the stat housing.
now that a Tee piece has been fitted coolant in the Tee is static that the probe is in contact with, not really flowing so it isnt ideal as it could be measuring a slightly lower temp

.... X 2

Probably better to buy/make, a joiner to fit into the heater hose or rad hose for the fan controller.

I read the same about the lack of flow passing over the sensors with the T-piece, I guess I'll wire up the push in radiator probe as a test to start with (it will only take a few minutes) and then look at a more robust solution e.g. radiator hose probe.

Cheers lads

[Tassie Jeeper]

ha, i use an engine watchdog in the cabin http://enginewatchdog.com/ it has saved me on two occasions already!

wish i had 1 of these when i cooked my engine:wall:

[Mopud]

wish i had 1 of these when i cooked my engine:wall:

Me too... that's how i ended up with the stroker :mrgreen: so not all bad..

Although it has saved this one a few times already

[Tassie Jeeper]

Me too... that's how i ended up with the stroker :mrgreen: so not all bad..

Although it has saved this one a few times already

my motor isnt terminal still runs great and quiet but chaffs lots of smoke and going uphill if u drive the boot in it makes lots of noise but nothing happens so im thinking it just needs rings and maybe valve guide seals.

but im thinking since i need a gearbox as well i might be in for a gen111 conversion when money allows ;)

best of luck getting ur temps right