Thermostat or water pump - JeepForum.com
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post #1 of 15 Old 07-02-2020, 03:10 PM Thread Starter
kerian159
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Thermostat or water pump

98 XJ 4.0 and if I sit at a drive thru or at a long light the temp will start to come up a bit above the 210 mark (I live in Florida so it's hot outside). Would this be a symptom of a dying thermostat or water pump? Another issue is anytime I drive it for a decent time after I shut it off it smells hot. Electrical fan is new and working. Clutch fan seems to be working (not sure how to test that)


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post #2 of 15 Old 07-02-2020, 03:51 PM
CJ7-Tim
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Temperature creep at idle, in stop-n-go traffic, or on the 4x4 trails is a symptom of a weak mechanical fan clutch.



The most important cooling system 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 chemical flushing/cleaning solution to remove mineral buildup or rust, flush with clean water, and then drain and fill the radiator with a fresh 50/50 coolant and water mix. With neglected cooling system you may have to flush several times.


Cooling system preventative maintenance:

-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. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace the fan or fan relay as needed.
-Inspect/test or replace the coolant temperature sensor that activates the e-fan.
-Consider replacing 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.
-Inspect all of the frost plugs in the block and the ones on the backside of the head for rust holes and coolant leakage.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat every few years with a genuine Jeep 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out radiator cap will allow not hold system pressure which can cause boil overs and/or allow the coolant flash over into to steam. You will likely see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.
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post #3 of 15 Old 07-02-2020, 04:36 PM
ChiliPalmer
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Quote:
Originally Posted by CJ7-Tim View Post
Temperature creep at idle, in stop-n-go traffic, or on the 4x4 trails is a symptom of a weak mechanical fan clutch.
All the research I have done suggests it is the fan clutch as well and I would agree with this. My radiator went out a couple of months ago and I replaced it and the t-stat, went back to the scene of the crime (where the radiator went out - in the mountains) and it still got so hot I had to pull over and let it cool down. I have a ZJ fan clutch in my backseat waiting to be installed. It is possible it's something else, but I've played with the fan shroud off and on and it makes a big difference in stop and go traffic, which leads to air flow, or lack thereof, as the main cause and a bad fan clutch will result in less airflow.



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Oh man Chili. I feel like a recovering addict that just had a bag of blow, a bottle of Jameson, and a sack dropped in his lap. You screwed me man!
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post #4 of 15 Old 07-02-2020, 04:51 PM
wildbill23c
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Most likely a bad fan clutch, or if it has an electric fan, a bad fan, relay, switch, etc. A water pump typically don't cause temp fluctuations like that, and a thermostat could if its sticking, but more likely just a worn out fan clutch and can easily be diagnosed, they'll start leaking oil out of them so the clutch may be covered in oil/dirt. If the fan just spins freely with absolutely no resistance when turned by hand its a good sign its worn out too...on the other hand you can get them where they lock up and sounds like a jet engine taking off, better than not working, but annoying and you lose power as a result.
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post #5 of 15 Old 07-03-2020, 01:48 AM
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A viscous clutch loses about 5 % of its stickiness each year if you do regular mileage, they just wear.

If yours is 30 years old then it is due for replacement.

They are not expensive, a new water pump, thermostat, radiator cap, hoses and viscous clutch will be a good investment. I would also have the radiator serviced / rodded at your local rad shop. Inspect the core plugs for leaking. With the correct coolant it should run fine.

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post #6 of 15 Old 07-03-2020, 03:56 AM
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I never had any problems with my '00 as far as overheating goes.
One day in internet land I came across this:


Well mine spun like a not properly working one would.
So I replaced it despite not having an problems.
Was considering the ZJ fan clutch but just went with a aftermarket stock one.
Napa one which best I can tell is a rebranded Hayden.
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post #7 of 15 Old 07-03-2020, 06:34 AM
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Quote:
Originally Posted by Ralph77 View Post
I never had any problems with my '00 as far as overheating goes.
One day in internet land I came across this:
.
Excellent video. Those spinning blades can fool you the fan works!!!

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post #8 of 15 Old 07-07-2020, 11:53 AM
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I finally replaced mine (I actually went with the ZJ one from NAPA) and spent the entire day exploring in the desert Saturday with zero issues. Had the AC on all day and never an issue, temp hovered around 210 all day. It wasn't exceptionally hot (sub 90 but above 80) but it was colder than that the last time out when it overheated.

That being said: at the very end of the day when I was parking at the campsite it did get hot and the only thing that changed was the approach to this campsite is seriously off cambe (in 20 yards it's up, down and left and right) so I believe I had an air pocket somewhere or what I really think happened was the overflow bottle allowed air in the system. It was FLAWLESS all day, it basically ran from 10AM until 5PM with the AC on without a blip and has been perfect since then. I'm going to try topping off the radiator and overflow bottle this week and see if I get more bubbles.



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Originally Posted by Sparrows View Post
Oh man Chili. I feel like a recovering addict that just had a bag of blow, a bottle of Jameson, and a sack dropped in his lap. You screwed me man!
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post #9 of 15 Old 07-08-2020, 08:42 AM Thread Starter
kerian159
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Xj

what did you replace? I checked my clutch fan and it stops turning within 2-5 seconds so I don't think it's that (for mine)

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post #10 of 15 Old 07-08-2020, 10:44 AM
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Quote:
Originally Posted by kerian159 View Post
what did you replace? I checked my clutch fan and it stops turning within 2-5 seconds so I don't think it's that (for mine)
Creeping to 215 is normal. If the fan clutch seems good, I'd use a good chemical flush like Blue Devil. It fixed my XJ problems. You wouldn't believe the crap that came out after the flush. Two years later my original 1999 radiator cracked and a bunch more crud was still in there.

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post #11 of 15 Old 07-09-2020, 10:12 AM
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Quote:
Originally Posted by kerian159 View Post
what did you replace? I checked my clutch fan and it stops turning within 2-5 seconds so I don't think it's that (for mine)
I didn't catch that it just creeps past the 210 mark, that's pretty normal and my Jeep will still do that when parked for extended times even with the extended idle on. I wouldn't worry too much about it.



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Oh man Chili. I feel like a recovering addict that just had a bag of blow, a bottle of Jameson, and a sack dropped in his lap. You screwed me man!
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post #12 of 15 Old 07-09-2020, 12:04 PM
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Quote:
Originally Posted by kerian159 View Post
what did you replace? I checked my clutch fan and it stops turning within 2-5 seconds so I don't think it's that (for mine)
If you are meaning.. when you spin the fan by hand and it stops spinning in 2 - 5 seconds then the fan clutch is shot.
When I spin my jeeps fan it has resistance against my hand when trying to spin it and then when I spin the fan and let go, it Immediatly Stops. (I will re-phrase that... it stops quickly, maybe 2 or 3 fan blades pass by before it stops the spin by hand)

If I were to keep my jeep long term and my clutch fan were to start to get bad I think I would Drop the Clutch part of the fan and replace it with a Clutch Fan Hub Eliminator (see below). I think my decision is based strongly on the fact the my engine has the #0331 head that can easily crack if there is an overheat situation and I would rather have a little worse gas mileage but also have some relief knowing the Fan is Always Turning when ever the engine is running But, that's just me.

https://www.ebay.com/itm/Clutch-Fan-...r/114269884685

Thank You,
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post #13 of 15 Old 07-10-2020, 08:31 AM Thread Starter
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Originally Posted by riderboy1961 View Post
If you are meaning.. when you spin the fan by hand and it stops spinning in 2 - 5 seconds then the fan clutch is shot.
When I spin my jeeps fan it has resistance against my hand when trying to spin it and then when I spin the fan and let go, it Immediatly Stops.

If I were to keep my jeep long term and my clutch fan were to start to get bad I think I would Drop the Clutch part of the fan and replace it with a Clutch Fan Hub Eliminator (see below). I think my decision is based strongly on the fact the my engine has the #0331 head that can easily crack if there is and overheat situation and I would rather have a little worse gas mileage but also have some relief knowing the Fan is Always Turning when ever the engine is running But, that's just me.

https://www.ebay.com/itm/Clutch-Fan-...r/114269884685
I tested it after shutting off the engine, I have not tried to turn it by hand yet (I guess I need to try that), if it's good it shouldn't turn by hand correct?

I'm actually still learning about these engines that have water moving through them i'm used to the air-cooled variety :-)

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post #14 of 15 Old 07-10-2020, 08:54 AM
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Originally Posted by kerian159 View Post
I tested it after shutting off the engine, I have not tried to turn it by hand yet (I guess I need to try that), if it's good it shouldn't turn by hand correct?

I'm actually still learning about these engines that have water moving through them i'm used to the air-cooled variety :-)

Just push a fan blade as fast as you can,quickly, and let go... it should have Some resistance And it should only spin maybe 2 or 3 blades before it stops. If it spins more or longer than that, your fan Clutch may be wearing or worn. Let us know the outcome of this.

I am just learning about these jeeps myself. However I Do have about 40 years of general automotive experience, including Aircraft maintenance.
I have only had this one for 4 months now (first jeep ever). I have learned quite a bit on this site on my jeep though!! There are many Highly knowledgeable folkes on here!!

Thank You,
Bo
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post #15 of 15 Old 07-10-2020, 09:19 AM
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Quote:
Originally Posted by kerian159 View Post
I tested it after shutting off the engine, I have not tried to turn it by hand yet (I guess I need to try that), if it's good it shouldn't turn by hand correct?

I'm actually still learning about these engines that have water moving through them i'm used to the air-cooled variety :-)
Can you post a video? If not, I can PM my number and I can post it for you. That way you could get more eyes on it for a better idea.

Quote:
Originally Posted by riderboy1961 View Post
Just push a fan blade as fast as you can,quickly, and let go... it should have Some resistance And it should only spin maybe 2 or 3 blades before it stops. If it spins more or longer than that, your fan Clutch may be wearing or worn. Let us know the outcome of this.

I am just learning about these jeeps myself. However I Do have about 40 years of general automotive experience, including Aircraft maintenance.
I have only had this one for 4 months now (first jeep ever). I have learned quite a bit on this site on my jeep though!! There are many Highly knowledgeable folkes on here!!
The people on here simply amaze me sometimes. I've been on here for quite a while but I'm still amazed at some of the info others post.



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Oh man Chili. I feel like a recovering addict that just had a bag of blow, a bottle of Jameson, and a sack dropped in his lap. You screwed me man!
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