Replace Water Pump+stat...still overheating! WHY!? -
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Unread 11-06-2012, 03:30 PM   #1
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1996 FSJ Cherokee 
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Replace Water Pump+stat...still overheating! WHY!?

I just replaced the water pump and thermostat in my 96 cherokee yet it keeps overheating. It takes a while for it to get hot maybe 10 minutes, but if im on the highway no problems whatsoever. Im stumped please help!

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Unread 11-06-2012, 03:32 PM   #2
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Is the fan working? Did you bleed all the air out?
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Unread 11-06-2012, 03:47 PM   #3
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did you replace the radiator? Have you flushed the cooling system? If you have no problems at highway speeds, it's your fan clutch
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Unread 11-06-2012, 03:55 PM   #4
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Mechanical fan clutch
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Unread 11-06-2012, 06:49 PM   #5
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2000 XJ Cherokee 
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Location: out in the garage - Minneapolis, Minnesota
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Service the cooling system, replace any weak or worn parts.

Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport, and dissipate heat, such as a low coolant level, loss of coolant (through internal or external leaks), poor heat conductivity inside the engine because of accumulated mineral deposits in the water jackets or radiator, a defective thermostat that doesn’t open, poor airflow through the radiator, a slipping fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller or even a defective radiator cap.

The cooling system is a group of related parts that depend on proper function from each of its component parts to keep the engine cool. Service the cooling system and replace any under-performing or suspected weak parts. Any component part of the cooling system that is not fully doing its job will stress the others and your cooling system will overheat. Temperature creep on the 4x4 trails, at idle, or in stop-n-go traffic points to a weak or failing mechanical fan clutch.
The most important maintenance item is to flush and refill the coolant periodically. Coolant should be replaced every 36,000 miles, or every two to three years. Anti-freeze has a number of additives that are designed to prevent corrosion in the cooling system, but they have a limited life span. The corrosion causes scale that eventually builds up and begins to clog the thin flat tubes in the radiator and heater core, causing the engine to eventually overheat.

-Use a flushing/cleaning solution and then drain and fill the radiator with a fresh 50/50 coolant and water mix. With a neglected cooling system you may have to flush several times.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat with a STANT or Robertshaw 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out cap will allow boil overs and/or allow the coolant flash over into to steam. You will see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.
-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.
-Inspect the electric cooling fan and the fan relay. Apply 12 volts and make sure the fan runs. Exchange the cooling fan relay with one of the others similar relays. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace the fan or relay as needed.
-Inspect/test or replace the coolant temperature sensor that activates the e-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.
-Inspect/replace the radiator hoses. Make sure the coiled wire is installed in the lower hose.

If you have covered all the points listed above and still have overheating issues, inspect the head for cracks and head gasket for leaks. Exhaust gasses entering the coolant can raise the temperature of the coolant or cause steam pockets in the coolant that will temporarily block the flow of coolant

Read more about cooling systems here –

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Unread 11-06-2012, 06:53 PM   #6
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i have put in a brand new thermostat and had it not work,, i have had dozens of people tell me never to trust a new thermostat,,, cj7 tim is the man, as always, but for inexpensive as it is,, buy another thermostat and try that
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Unread 11-07-2012, 08:59 AM   #7
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All the advice above is super helpful as always!! If all that checks out ok, but you are still running hot, then consider installing hood vents. I did and it made a big difference for my XJ . Keep on it and you'll figure it out !!
'01 XJ Sport, RE 3.5 Super Ride w/ full Leaf pack, BFG KM2s,RE Adj Track Bar & Stabi Shock, Bilstein 5100s,TBS,Tranny Cooler & gage,etc etc etc
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Unread 11-07-2012, 09:43 AM   #8
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1996 XJ Cherokee 
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The "runs fine on freeway but overheats at a stoplight" is almost always a mechanical fan clutch.

Easy way is to hot/cold test it, or just take off the shroud and see if the clutch looks wet and dirty (leaking). If its over 5-10 yrs old I'd replace it anyways. They cost like 40$. My 96 just got a new one 2 months back and it was the original I was replacing. I would run fine at speed but temp would creep up when at a stoplight.
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Unread 11-08-2012, 12:57 PM   #9
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Thanks so much for all the advice! i will replace the fan clutch and see if that helps! as far as i know it is the original so i should replace it anyways
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Unread 11-19-2015, 08:50 PM   #10
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2007 WK 
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This thread is pretty old, but I'm not sure if I should start a new thread or not.. But anyways... I've scoured the internet for anyone having the same issues as me and I've yet to find something conclusive. I'll keep this as brief as possible and appreciate any and all help.

Got my '07 WK GC 4 years ago at 40k miles, once in a blue moon (once every other month or less) I'd get a brief "Transmission Over Temp" warning. I'd pull over, let it cool, restart and I'm good. Fast forward to this last summer.. The Jeep started sounding terrible in 1st gear, tranny over temp warnings were much more frequent. Changed out the nasty tranny fluid, things seemed to improve vastly over time. Fast forward to late September to now, and if I shut the Jeep off and back on again multiple times, it overheats, and won't crank up, and honestly sounds horrific trying to crank. The whole thing shakes. It turns, just won't fire. When I say cut it off and back on a few times, I mean if I had to stop by multiple stores for multiple errands within a few hours, around the 3rd or 4th off and on cycle would begin giving me issues and not cranking. I'd have to let it sit for about 30+ mins, then it would purr to life easily.

Took it in last week for the recall on its ignition and when they asked about my check engine light, I told them what was happening, and that sometimes on a cold start-n-drive, the temp gauge would stay cold, and eventually a "check gauges" warning would come up with the lightning bold red warning light. I would pull over, turn it off. Let is sit for about five mins, crank it back up and the temp would go to normal. Check engine stayed on.

After the ignition was switched out, the had done their enormous multipoint whatever inspection and told me the water pump was bad and the system was leaking. Ah. It all makes sense now. Kind of. Anyways, I get the parts from partsgeek, (ACDelco pump and a thermostat) and do the job. Here's where it gets interesting. Flush the radiator and most all of the coolant from the radiator comes out, but hardly any from the reservoir comes out. Now I'm glad I got that thermo. Change the water pump out, change the thermo, and start her up. She struggled at first, tried again then she purred right up. didn't think much of it. Let it run for 15 mins. Stopped, cooled down, re-flushed to try and get the reservoir empty, no luck. Screw it. I need gas. Drive 2 miles to the Sunoco and I'm literally red-lining by the time I get there... Son of a...

So, I check everything, and the water I had dumped into the reservoir to help flush earlier was ALL GONE. Score. All that crap is in the system and now I can actually flush it all out. The new thermo works. Go to crank it and rats, it won't crank. It's doing the same shakey psuedo-fire up it was doing after I cut if off and back multiple times throughout the day. I tried to crank it for 20 mins. then I said screw it, and I added some water and coolant for the hey of it and it starts up on the second try. Not sure what that had to with it, but whatever, it gets me back to the house. By the time I get 2 miles back to the house I'm red-lining again. Flush everything out, this time the reservoir empties out. But I think the new thermo (which looked cruddy compared to the old one, which really looked pristine when I took it out) might have been giving me issues, so I put the old one back in. Try to crank, no go. Try for another 20 mins. No go. Let it sit for 30 minutes and it cranks up in no time. Except it still overheats when I drive it. Not at idling, but when I drive it. Heat doesn't work now either. Lemme recap.

Stage One (First three and a half years) of ownership:
- Rarely says tranny over temp. pull over, restart it's fine.

Stage Two (3.5-3.7 yrs) of ownership:
- Had dirty tranny issues (live at the beach) no issues starting. Changed out tranny fluid, cleaned filter, eventually got better. Still over temp'd every now and then.

Stage Three (3.7yrs to now (4.0)) of ownership:
- Starting convulsing when trying to start for the 3rd and 4th time in one day. Starts up fine after it's been sitting for a while. Over Temps quickly when idling now. Driving is fine.

Stage Four (now) of ownership:
- Replaced water pump, flushed radiator, and now it will NOT start after it was just turned off. Will start after it's sat for 30+ mins, Overheats within 5 minutes of driving. Smells burning. Does NOT overheat when idling.

I'm completely lost guys. I don't think it's a head gasket, my oil looks clean. Could I have gotten a bad water pump? I was having many of these issues before the new water pump though... And could my water bump bearing in the block be bad? Maybe the impeller? Is it something else??

I'm lost. Thanks guys. I hate the post is so long, but there's great info in this thread, and I wanna make sure I've given as much info as possible in this initial post to avoid too much back and forth.

Thanks again. I'm desperate. And cheap.
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Unread 11-19-2015, 11:31 PM   #11
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To the poster above.

Replace your crank position sensor. Replace your thermostat sending unit (Temp sensor)

And why didnt you remove the overflow and wash it out? Sucking it into the system was a bad idea.
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96 cherokee , cooling system , overheating , thermostat , water pump

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