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Fan clutch or coolant flush first?

red02tj

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Looking for some advice on which todo first to fix my high temps on my 02 (35k, original radiator). As long as I’m moving, OBDII shows ~210, when I idle, temps will creep up to ~235. Coolant was replaced last October.

Should I replace the fan clutch or do a full coolant flush first?

FWIW Is still in the 90s in GA.

Thanks
 

freedom_in_4low

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If it's only sitting still that it gets warm, I'd 100% do the fan clutch first. It's cheap and it's quicker to do, and since the problem is occurring specifically when the fan is in play, it's a reasonably likely culprit.

I've personally never had a coolant flush actually make one iota of difference in cooling system performance. Not that I think they don't work because I work in heat transfer so I know the impact of heat exchanger fouling... I just think that I haven't done one on a vehicle that was really in dire need of one.
 

TexasTJ2004

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I am dealing with my overheat issues, which were also temperature going high in idle only, not when I drive. When I was in idle with ac on, it would start to creep north of 210 very fast. Fan clutch is new (Hayden 2771), thermostat is Mopar new, radiator is autozone crap.
I flushed (blue devil and 2 rounds of thermocure) with full engine block drain plug and it did improve.
However,
Then I found that my water pump is leaking, and now replacing a water pump.
Also, I found that heater core is leaking, so I bypassed it.
 
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red02tj

red02tj

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Of course after I do the fan clutch, temps drop back into the 70s. I did a test ride for 15min and let idle with AC on for 30min and I topped out at 226. I guess a real test will wait until next summer.
 

Irun

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Of course after I do the fan clutch, temps drop back into the 70s. I did a test ride for 15min and let idle with AC on for 30min and I topped out at 226. I guess a real test will wait until next summer.

Why wait? Ignoring the cooling system can be result in a blown head gasket or cooked engine. It's best to take care of any possible issues immediately.
 
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red02tj

red02tj

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Why wait? Ignoring the cooling system can be result in a blown head gasket or cooked engine. It's best to take care of any possible issues immediately.

I meant that in I don’t have any temp issues driving, no coolant loss and no milkshake in the oil. I only notice higher temps at idle in the 90+ degree weather, so I did the fan clutch last week and after 30min of idle it was at 226. Coolant was replaced last October. And now the weather has dropped 20+ degrees.

Certainly open to other/next suggestions.
 

Irun

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I saw the comment from @freedom_in_4low, but given the low miles on your Jeep I'd be doing a flush. I've used this stuff a couple times and was surprised just how much came out in the process. Just be sure to follow the process as it's written.

 

JKP

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I meant that in I don’t have any temp issues driving, no coolant loss and no milkshake in the oil. I only notice higher temps at idle in the 90+ degree weather, so I did the fan clutch last week and after 30min of idle it was at 226. Coolant was replaced last October. And now the weather has dropped 20+ degrees.

Certainly open to other/next suggestions.

That's def not normal. Spent 2 hrs idling 10 mi over a mtn when I24 was shut down due to helicopter crash earlier this yr and mine never got a needles width over 210 on the gauge and 215 or so on the OBDII.

Do you know the history? How did the old coolant look when it was changed?

Original water pump?
 
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red02tj

red02tj

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That's def not normal. Spent 2 hrs idling 10 mi over a mtn when I24 was shut down due to helicopter crash earlier this yr and mine never got a needles width over 210 on the gauge and 215 or so on the OBDII.

Do you know the history? How did the old coolant look when it was changed?

Original water pump?

History is spotty, I picked it up last October with ~32k on the clock after it was mostly parked during the PO’s divorce. I did the typical fluid changes when I got it last year + replaced the rad cap with a new stant after the coolant was changed. Attached is what the coolant looked like before it was changed last year. Everything I’ve worked on has been original, so I’m assuming the water pump is as well.

Thermocure is in order for this weekend.

C2750B7B-6746-4E71-B158-E6878C1466F4.jpeg
 

JKP

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Look for good circulation when you do the thermocure. My buddy never changed his coolant and the impeller corroded/cavitated away! His wife could get to work before it got hot amazingly enough.
 

PRNDL

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History is spotty, I picked it up last October with ~32k on the clock after it was mostly parked during the PO’s divorce. I did the typical fluid changes when I got it last year + replaced the rad cap with a new stant after the coolant was changed. Attached is what the coolant looked like before it was changed last year. Everything I’ve worked on has been original, so I’m assuming the water pump is as well.

Thermocure is in order for this weekend.

View attachment 365026

You might remember my thermocure results.

I'm a believer. At 136k and on a very not new water pump and radiator, I have had zero cooling issues all summer.
 
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TexasTJ2004

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History is spotty, I picked it up last October with ~32k on the clock after it was mostly parked during the PO’s divorce. I did the typical fluid changes when I got it last year + replaced the rad cap with a new stant after the coolant was changed. Attached is what the coolant looked like before it was changed last year. Everything I’ve worked on has been original, so I’m assuming the water pump is as well.

Thermocure is in order for this weekend.

View attachment 365026

Your coolant looks horrible
 

TexasTJ2004

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When I did flush, I opened the drain plug in the block, drained all the coolant, then flushed with water, then put distilled water with BlueDevil, flushed for like a day, and then ran 3 sets of thermocure flushes.
At the end the engine from inside looked like new.
I think that if you do the flush yourself, drain the block. All you need is 8mm square socket
 
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freedom_in_4low

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I saw the comment from @freedom_in_4low, but given the low miles on your Jeep I'd be doing a flush. I've used this stuff a couple times and was surprised just how much came out in the process. Just be sure to follow the process as it's written.

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I certainly didn't mean to to imply that a flush wouldn't be helpful, just that a fan clutch could explain the symptoms and was less expensive (or at least similar) and less time consuming than a flush, so I would try that first.

Now that I've seen what the coolant looked like at time of purchase I'd say absolutely a thorough flush is in order. While I did say I've never noticed a benefit from a flush, I also have never had one where the coolant was opaque enough that I couldn't see the aluminum in the top of the radiator.
 
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red02tj

red02tj

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I certainly didn't mean to to imply that a flush wouldn't be helpful, just that a fan clutch could explain the symptoms and was less expensive (or at least similar) and less time consuming than a flush, so I would try that first.

Now that I've seen what the coolant looked like at time of purchase I'd say absolutely a thorough flush is in order. While I did say I've never noticed a benefit from a flush, I also have never had one where the coolant was opaque enough that I couldn't see the aluminum in the top of the radiator.

All good, fan clutch gave me a place to start. Thermocure is up next.
 

cpwolf

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All good, fan clutch gave me a place to start. Thermocure is up next.

I would take out the Thermostat before putting in the Thermocure. Put it in, that way it can run and will move around without the need to get it hit over and over. Leave it In a day, then drain, fill, 5 mins, drain, until it runs pretty clear.

If you leave the thermostat in, you have to let it come to temp to get I to circulate, and then it’s hot AF, and on and on. Way easier without it.

Yours looked solid rust water, definitely looks like Thermocure will be big help.
 

PRNDL

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When I did flush, I opened the drain plug in the block, drained all the coolant, then flushed with water, then put distilled water with BlueDevil, flushed for like a day, and then ran 3 sets of thermocure flushes.
At the end the engine from inside looked like new.
I think that if you do the flush yourself, drain the block. All you need is 8mm square socket

Definitely drain the block. Its a little bit of a hassle, but worth it.