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Unread 01-04-2008, 08:28 AM   #1
RednekWrangler
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Wrangler has poor heat and runs cool

My 94 wranger 2.5l has poor heat. Temp gauge goes only up to 125 degrees when warmed up. I replaced the themostat and radiator cap, but the engine still runs cool. After vehicle sits with engie off for a few minutes after driving, you can feel the engine getting warmer and temp gauge goes up to 180 degees. as soon as you start the engine it cools back down. Any help appreciated it was 10 below zero this morning. Thanks.

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Unread 01-04-2008, 09:14 AM   #2
Big-n-Broke-YJ
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sounds to me like you: have a defective coolant temp sending unit or gauge (125 isnt accurate for a driving tempature) and perhaps you or the previous owner removed the thermostat..... that or it's stuck open...

with only 1 post on this ofurm nobody is goign to know of your mechanical abilities.... are you familiar with the thermostat and thermostat housing? do you think you can figure out how to replace the thermostat on your own or do you need a quick guide?

Go buy a new 180 degree thermostat from your local parts store ($7-$12 depending on what brand you buy), a new thermostat housing gasket (under $1), and some ultra grey rtv just in case the new gasket doesn't seal for some reason.

if it was me, i'd buy a coolant temp sending unit first so i could monitor my engine temperature before and after the thermostat swap. then again, i'd probably test the sending unit first

the sending unit for the gauge is located on the top of the engine head, driver's side, at the very back corner... it's connector faces up... the sensor on the thermostat housing is for the engine computer and has nothing to do with your gauge... ignore it for now unless you jeep is running rough in which case it may be defective.

to test sensor for the guage:
  1. Turn ignition switch to Run position.
  2. Disconnect electrical connector from coolant temperature sender.
  3. Touch connector to engine block (ground). Gauge should read at high end of scale.
  4. When connector is not touching ground, gauge should read at low end of scale. If gauge functions properly, replace sensor; if not, continue with procedure.
  5. Check circuit between sensor and gauge for an open. If wiring is satisfactory, replace gauge.



-Erik
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Unread 01-04-2008, 09:25 AM   #3
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I would also check the fan clutch asuming you have one.
If the fan is constantly turning because the clutch is solid you will also run too cool.
When I was in the great white north I would block 50% of my radiator with cardboard to help keep the engine up to temp.

Dwayne
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Unread 01-04-2008, 09:41 AM   #4
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Another vote for a locked up fan clutch, (since the thermostat was already replaced). Not many "My Jeep engine run too cool" threads on here; consider yourself a bit lucky!
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Unread 01-04-2008, 10:17 AM   #5
Big-n-Broke-YJ
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i haven't had a fan clutch in years... forgot about that possibility... a locked up fan clutch will also rob your engine of lots of power.... does it feel sluggish?





courtesy of alldata:

The fan drive clutch is a fluid coupling containing silicone oil. Fan speed is regulated by the torque-carrying capacity of the silicone oil. The more silicone oil in the coupling, the greater the fan speed, and the less silicone oil, the slower the fan speed.
The fan drive clutch uses a heat-sensitive, coiled bimetallic spring connected to an opening plate. This unit causes the fan speed to increase with a rise in temperature and to decrease as temperature decreases.


Fan clutch noise can sometimes be noticed when clutch is engaged for maximum cooling. Clutch noise is also noticeable within the first few minutes after starting engine while clutch is redistributing the silicone fluid back to its normal, disengaged operating condition after settling for long periods of time (overnight). However, continuous fan noise or an excessive roar indicates the clutch assembly is locked-up due to internal failure. This condition can be checked by attempting to manually rotate fan. If fan cannot be rotated manually or there is a rough, abrasive feel as fan is rotated, the clutch should be replaced.
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'89 Wrangler, 4.0/AW4, 106" Wheelbase, SOA, custom XJ packs, 2" Body. Front High Pinion Dana 44 w/yukon super-joints, chromo inners and outers, and a Lincoln Locker. Rear Dana 60 w/Yukon 1.5" 35 Spline chomo shafts and detroit locker. 5.38 Yukon Gears. Hydro-Assist, 39.5x18" Boggers on 15x12 RockKrawler's w/ 2.75" of backspacing. Comp cut, tube fenders, custom bumpers and rock sliders, fuel cell, CB, Stewart Warner Gauges, SmittyBilt XRC8 Winch, 140 Amp CS-144 Alternator, Electric Fan, and a cooler of beer. 3897 lbs

March 1st, 8pm. WILMINGTON, NC MEET & GREET @ HOOTERS!
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Unread 01-04-2008, 10:49 AM   #6
RednekWrangler
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I've replaced the thermostat already. The fan clutch turns freely and never seems to lock up. I now the reason I'm not getting good heat is because the engine is not running hot enough. The gauge is reading properly. All the hoses feel barely warm after running down the highway. After turning off the engine you can feel the hot coolant coming into the hoses. I was just hoping some one had seen this before, before I replace everything. I had great heat one second and the next second barely any heat and the gauge stays low. I'm a Toyota technician at a dealership who drives a Jeep. Thanks
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Unread 01-04-2008, 11:47 AM   #7
MLJeeper
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When mine did this, it was the fan clutch causing my issues.
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Any video of the sound?
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Unread 01-04-2008, 12:37 PM   #8
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Just gonna ask, not very likely, did you put the tstat in backwards and what * tstat did you use???
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Unread 01-04-2008, 01:26 PM   #9
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if the thermostat is working properly than it will shut and block coolant flow to the radiator until it reaches it's specified temp.....

sounds like a tstat is stuck open, you have a baller 17,000 cure aluminum racing radiator & a hellacious SPAL electric fan, or it's colder than antarctica where you live and that's just part of life you'll have to deal with.... but i'm goign to venture to say it's probably the thermostat....
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'89 Wrangler, 4.0/AW4, 106" Wheelbase, SOA, custom XJ packs, 2" Body. Front High Pinion Dana 44 w/yukon super-joints, chromo inners and outers, and a Lincoln Locker. Rear Dana 60 w/Yukon 1.5" 35 Spline chomo shafts and detroit locker. 5.38 Yukon Gears. Hydro-Assist, 39.5x18" Boggers on 15x12 RockKrawler's w/ 2.75" of backspacing. Comp cut, tube fenders, custom bumpers and rock sliders, fuel cell, CB, Stewart Warner Gauges, SmittyBilt XRC8 Winch, 140 Amp CS-144 Alternator, Electric Fan, and a cooler of beer. 3897 lbs

March 1st, 8pm. WILMINGTON, NC MEET & GREET @ HOOTERS!
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Unread 01-04-2008, 03:59 PM   #10
RednekWrangler
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The thermostat is in properly. It's doing the exact same thing that the old one did, no difference. I thought that this would be an easy fix. But with my luck I wouldn't expect anything different. Thanks.
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Unread 01-04-2008, 04:05 PM   #11
Big-n-Broke-YJ
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take the thermostat out.

put it in a pot of water.

put a thermoter in the pot.

bring the pot of water to a boil

watch the t-stat and see what temperature it opens at....

then turn off the stove and see what temp it closes at....



i swear this sounds 100% typical of a failed tstat....

i could be wrong but i swear i really think it is impossible for your engine to truly be running @ 125 degrees F. i mean, my lawnmower runs hotter than that.....
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'89 Wrangler, 4.0/AW4, 106" Wheelbase, SOA, custom XJ packs, 2" Body. Front High Pinion Dana 44 w/yukon super-joints, chromo inners and outers, and a Lincoln Locker. Rear Dana 60 w/Yukon 1.5" 35 Spline chomo shafts and detroit locker. 5.38 Yukon Gears. Hydro-Assist, 39.5x18" Boggers on 15x12 RockKrawler's w/ 2.75" of backspacing. Comp cut, tube fenders, custom bumpers and rock sliders, fuel cell, CB, Stewart Warner Gauges, SmittyBilt XRC8 Winch, 140 Amp CS-144 Alternator, Electric Fan, and a cooler of beer. 3897 lbs

March 1st, 8pm. WILMINGTON, NC MEET & GREET @ HOOTERS!
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Unread 01-04-2008, 04:55 PM   #12
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Quote:
Originally Posted by Big-n-Broke-YJ
take the thermostat out.

put it in a pot of water.

put a thermoter in the pot.

bring the pot of water to a boil

watch the t-stat and see what temperature it opens at....

then turn off the stove and see what temp it closes at....



i swear this sounds 100% typical of a failed tstat....

i could be wrong but i swear i really think it is impossible for your engine to truly be running @ 125 degrees F. i mean, my lawnmower runs hotter than that.....

That method doesn't work with a 195* stat, tried and failed 3 good stats before I found that out lol.
If everything else checks out I would block 50% of the rad with cardboard.

Dwayne
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Unread 01-04-2008, 05:20 PM   #13
Big-n-Broke-YJ
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that's odd.... maybe it has something to do with pressure as well as temp?

it worked for my 180... doesn't the factory recommend a 180 tstat anyway?
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'89 Wrangler, 4.0/AW4, 106" Wheelbase, SOA, custom XJ packs, 2" Body. Front High Pinion Dana 44 w/yukon super-joints, chromo inners and outers, and a Lincoln Locker. Rear Dana 60 w/Yukon 1.5" 35 Spline chomo shafts and detroit locker. 5.38 Yukon Gears. Hydro-Assist, 39.5x18" Boggers on 15x12 RockKrawler's w/ 2.75" of backspacing. Comp cut, tube fenders, custom bumpers and rock sliders, fuel cell, CB, Stewart Warner Gauges, SmittyBilt XRC8 Winch, 140 Amp CS-144 Alternator, Electric Fan, and a cooler of beer. 3897 lbs

March 1st, 8pm. WILMINGTON, NC MEET & GREET @ HOOTERS!
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Unread 01-04-2008, 05:37 PM   #14
Nelliebelle7
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My jeep runs very cool too. I hit a deer and split the radiator. I replaced it with a new 3 row brass radiator and it's been very cool since. It gets up to temp in the summer, but not in winter.
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Unread 01-04-2008, 05:42 PM   #15
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Quote:
Originally Posted by Big-n-Broke-YJ
that's odd.... maybe it has something to do with pressure as well as temp?

it worked for my 180... doesn't the factory recommend a 180 tstat anyway?

From the factory, jeep puts in a 195* thermostat.
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