Overheating only on Highway

themauler · Jun 25, 2012

I have read through a of the threads dealing with overheating and to check thermostat and fan clutch etc. but my jeep is a 92 4.0/aw4/231 lifted 31 streeties on 4.56 gears. stacked plate tranny cooler infront of the efan. my jeep does great cooling wise in town, idling, cruising around, except on trails (hot days) and highway with the a/c on.

my jeep goes a little like this on the highway.....windows up a/c on doing 65 which is about 2700 rpms with the gear tire combo holds right about 210degrees. the second i start going up any hill the temp starts creeping then if the hill on the highway doesnt end in about three minutes the needle will be right next to the red zone and that is when i have to roll the windows down and turn the heat on.

and for trails everyone overheats so i deal with it :skull1:

as of right now the radiator is a two row with plastic tanks(two years old) and all cooling system components were replaced a year ago. and yes the efan works great

am i going in the right direction looking for an all metal three row radiator?

nick

O-Gauge Steamer · Jun 25, 2012

Start with the basics. When was the last time the cooling system had a chemical clean? If it has been over two years, I would start there. I know you replaced parts but, and it is a big but, if the system was not chemically cleaned prior to the installation of the new components there is the very large risk of contaminating the new parts. Whaen was the last time the fins were cleaned?

I flush and refill every year and do a chem clean every other year.

But then, I'm an Old Guy with Bad Habits...

Overheating is usually not enough air across the radiator (dirty fins, external) or it is not enough coolant through the radiator (dirty tubes, internal). Rarely is it the pump or the T-Stat. Though it can be.

I can give a concrete example from my Heep. When the I fitted the electric water pump into it, I had issues holding the 90C (194F) setpoint. The issue traced to not enough air across the radiator. As soon as I cut holes in the hood (relieves the pressure under the hood) flow was improved and the Heep holds the setpoint. I have a CSF three row all metal radiator in it.

The other thing I found was a 5C average temperature drop just by remoting the transmission cooler out from in front of the radiator. There is a reason the Factory Aux Trans Cooler sits below the radiator...

In Fahrenheit, my Heep operates between 194F and 201F.

beastlydumass · Jun 25, 2012

i would also do a chemical clean. i used clr put about half a bottle in it and let it idle to operating temp then let it sit long enough so you drain the hole system without buring uraelf then stuff a hose in the cap with drain open a little and flush everything out then park facing up a hill and fill. make sure to get ALL the air out of the system. if this dont help i would look for a pin leak or something that drops pressure wen under a load. if fans work and u have nothing blocking flow past the fins then u should have no problem. when running the a/c on a hot its pound to run hot if not overheat after a while cause the condensor the sits in front of the rad will start to put off a alot of heat.

Boss Cherokee · Jun 25, 2012

o-gauge-steamer said:
Start with the basics. When was the last time the cooling system had a chemical clean? If it has been over two years, I would start there. I know you replaced parts but, and it is a big but, if the system was not chemically cleaned prior to the installation of the new components there is the very large risk of contaminating the new parts. Whaen was the last time the fins were cleaned?

I flush and refill every year and do a chem clean every other year.

But then, I'm an Old Guy with Bad Habits...

Overheating is usually not enough air across the radiator (dirty fins, external) or it is not enough coolant through the radiator (dirty tubes, internal). Rarely is it the pump or the T-Stat. Though it can be.

I can give a concrete example from my Heep. When the I fitted the electric water pump into it, I had issues holding the 90C (194F) setpoint. The issue traced to not enough air across the radiator. As soon as I cut holes in the hood (relieves the pressure under the hood) flow was improved and the Heep holds the setpoint. I have a CSF three row all metal radiator in it.

The other thing I found was a 5C average temperature drop just by remoting the transmission cooler out from in front of the radiator. There is a reason the Factory Aux Trans Cooler sits below the radiator...

In Fahrenheit, my Heep operates between 194F and 201F.

So I will be installing a remote trans cooler with a fan attached away from radiator possibly under the hood will drop my temp. at least 5 degrees? If so I will do it this weekend!

carves · Jun 26, 2012

themauler said:
I have read through a of the threads dealing with overheating and to check thermostat and fan clutch etc. but my jeep is a 92 4.0/aw4/231 lifted 31 streeties on 4.56 gears. stacked plate tranny cooler infront of the efan. my jeep does great cooling wise in town, idling, cruising around, except on trails (hot days) and highway with the a/c on.

my jeep goes a little like this on the highway.....windows up a/c on doing 65 which is about 2700 rpms with the gear tire combo holds right about 210degrees. the second i start going up any hill the temp starts creeping then if the hill on the highway doesnt end in about three minutes the needle will be right next to the red zone and that is when i have to roll the windows down and turn the heat on.

and for trails everyone overheats so i deal with it :skull1:

as of right now the radiator is a two row with plastic tanks(two years old) and all cooling system components were replaced a year ago. and yes the efan works great

am i going in the right direction looking for an all metal three row radiator?

nick

2 row all metal will probably be fine. My vote is Copper over Al ... but the choice is yours.

X 2 with O-Gauge regarding maintenace.

2row copper rad,
190* t'stat,
10/90 coolant,
Stock equivalent, fanclutch & waterpump,
No hood vents (just small gaps at the hood rear corners),
10x12 tranny cooler blocking the rad,
Aftermarket exhaust headers/extractors,

and this is what my scangauge displays all year round, on & offroad ... in 30* to 110*+ weather.

Vehicle is basically stock tho.

Obviously, its only the average, constant running temp ... As theres a coupla degrees variation, now & then - depending on winter/summer temps or engine load.

Boss Cherokee said:
So I will be installing a remote trans cooler with a fan attached away from radiator possibly under the hood will drop my temp. at least 5 degrees? If so I will do it this weekend!

A 10x12 stacked plate cooler blocking the rad doesnt cause diddlysquat running temp problems on mine.
Temp sensors on both ends of the rad - didnt display any running temp increases worth fussing over.

Not to say it wont cause issues on some vehicles of course ... but its best to monitor before & after temps of YOUR vehicle ... to see if YOU get an "improvement" with a mod.

Ecomike · Jun 26, 2012

Sounds to me like an air flow problem on the incline. Hot likes to rise, so the steeper the incline the more important air flow becomes, and vehicle speed. What is the status of the cowlings? Tried sealing any open areas where the air can by pass the radiator?

The CSF 3 row copper-brass is well worth the money!!!!

Is the Tranny cooler blocking air flow in the radiator too much?

Sounds like you have most everything else covered.

You might try the ZJ fan clutch too.

themauler · Jul 16, 2012

Re: Overheating only on Highway FOLLOW UP

Well I went with my gut and ordered the csf three row heavy duty all metal radiator from radiator barn and it is working great! Today doing 65 in the hills of virginia with the ac on the temp never went over 210.

crappy iphone pic

yes my fan clutch is a little closer to the radiator than I like but I got some new brown dog motor mounts on the way :rof:

Overheating only on Highway

themauler

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O-Gauge Steamer

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beastlydumass

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Boss Cherokee

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carves

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Ecomike

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themauler

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