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Old 05-26-2012, 07:58 AM   #1
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Angry Thermostat

My 03 is running hot so I thought i'd try the Thermostat first as it's the least expensive option..... Well apparently that didn't cure my prob. The question today is I've been looking at past posts to find an answer as not to repost a question that has been discussed. The thermostat did not have a weap hole or air hole in it that i've read so much about in old posts. Could that be part of the problem. It was the most expensive TS they sold. For all that trouble didn't want to cheap out. Any suggestions. I don't know if that is the prob. or if its the radiator or WP. This just cost me a weekend in the mountains as we had to limp back home and give up a rental in the mnt.$$$ lost on that.

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Old 05-26-2012, 08:22 AM   #2
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From my understanding you should only replace the thermostat with an exact factory replacement. . . i have heard some of the "better" ones are quite better. . .

Have you done a radiator flush?

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Old 05-26-2012, 08:30 AM   #3
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Is it actually running hot or does gauge just say its hot? Do you have an electric fan or motor mounted fan? Do you have enough coolant and like gunner said have you done a flush?
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Old 05-26-2012, 08:32 AM   #4
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Quote:
Originally Posted by TJgunner
From my understanding you should only replace the thermostat with an exact factory replacement. . . i have heard some of the "better" ones are quite better. . .

Have you done a radiator flush?
I want to say the tj uses a 190 thermo. I have heard of people putting in 160 thermos to reduce the chance of overheating.
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Old 05-26-2012, 08:49 AM   #5
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I want to say the tj uses a 190 thermo. I have heard of people putting in 160 thermos to reduce the chance of overheating.
the TJ's thermo is 195, so the engine's normal operating temp is 195-210.

don't use a 160 thermo, you're asking for computer issues.
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Old 05-26-2012, 09:09 AM   #6
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I have heard of people putting in 160 thermos to reduce the chance of overheating.
Ask some of those people how a fully open 160 thermostat prevents overheating any better than a fully open 195 thermostat.
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Old 05-26-2012, 10:36 AM   #7
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Not only will a 160 degree thermostat not prevent overheating when compared to a properly functioning 195 degree thermostat, for the reason posted by tangofox, the engine computer is programmed around a 195 degree thermostat. That means running a 160 degree thermostat can cause the Jeep to stay in a warm-up stage too long causing the engine to run too rich, not to mention taking the engine too long to warm up on cold mornings which means your heater won't work as well. In some situations, running a 160 degree thermostat could actually generate a Check Engine light. And on REALLY cold days, the engine would never fully warm up and the heater would have more trouble warming the interior and take longer to do so.
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Old 05-26-2012, 10:41 AM   #8
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let me ask some questions: how hot is it running, in the red? what if anything changed between it running normal vs hot? With no thermo does it still run hot? Is there air in the system that needs burped out?
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Old 05-26-2012, 11:18 AM   #9
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Also, When is it running hot, at freeway speed but ok at slower speeds, or at slow speeds but ok at freeway speeds, or all of the time where a simple rad cap could be the problem?

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Old 05-26-2012, 11:21 AM   #10
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Quote:
Originally Posted by tangofox007

Ask some of those people how a fully open 160 thermostat prevents overheating any better than a fully open 195 thermostat.
How would it not? It's gonna be open sooner and stay open longer.
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Old 05-26-2012, 11:27 AM   #11
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Also, When is it running hot, at freeway speed but ok at slower speeds, or at slow speeds but ok at freeway speeds, or all of the time where a simple rad cap could be the problem?

Donn
These questions will need to be answered and then I can help. I learned a lot in my journey of replacing thermostat, water pump, fan clutch, radiator, radiator cap and hoses.

My problem is fixed but expensive. Give us your exact overheating scenario and we can help.
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Old 05-26-2012, 12:50 PM   #12
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How would it not? It's gonna be open sooner and stay open longer.
Trust us... while it may seem counter-intuitive to some, a lower temp thermostat doesn't help prevent an engine from overheating. No matter if it opens at 160 or 195 degrees, both of those temperature thermostats are already wide open well below the engine's normal operating temperature. If an engine is overheating, the coolant temperature is already well over the opening temperature of both of them.

Overheating is NEVER EVER the fault of a properly operating correct temperature thermostat. Installing a cooler thermstat in a misguided attempt to prevent or help reduce overheating is like putting a band-aid on a finger to help prevent a toothache.

If an engine is overheating, fix the real root cause of the problem. Air in the cooling system, hard water deposits blocking coolant flow in the radiator, mud/dirt in the radiator's cooling fins blocking air flow, a stuck/defective thermostat, defective fan clutch, etc.
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Old 05-26-2012, 01:46 PM   #13
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One reason for the lower-rated thermostat myth is that, when people try it, it seems to work. They replace a failed thermostat with a good one, and give all the credit to the lower temp rating.

Same thing with spark plugs. They have worn out Brand X, which they replace with new, properly gapped Brand Y. Engine runs better. Conclusion: Brand Y is so much better than Brand X.
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Old 05-26-2012, 04:45 PM   #14
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hi everyone, let me give a few more details and todays update. We bought it in cold weather and haven't driven it much but now that it's in the 90's we are driving it some. It stayed at 210 until last week when at highway speeds it creaped up to the red line and just as fast would drop back to 210. it did this for the hr. drive home in which we ran the heat ( what i've heard helps) Well i put in a 195 thermostat thinking that would fix it....or i had a faulty hot reading. Well yesterday I put a new radiator cap on it and we packed up to go on a road trip and it started again so we turned back. It hit the red so i pulled over to cool it off and it went to the far end of Hot and the engine light came on. so we sat for a while and it really was Hot. i could hear the water boiling or rumbling so i knew it was hot. Planning to do a coolant flush today when I read about air pockets etc and found i'd pay half the cost of the dealer doing it my self so I took it to the dlr. didn't get hot on 25 mile hwy trip. coming home it was a touch over 210 so i tried a test and turned the A\C on and it got about a third of the way to the hot. I checked the fan clutch and it isn't oily and doesn't spin freely and has some resistance to it. So now i've got a new radiator cap, thermostat and newly flushed system. The wp doesn't make any noise and there is no coolant leaking anywhere. I'm not sure what to try next. I'm not a wrench turner so i don't want to tackle a job that isn't needed but i don't know what to look for next. oh its 03 sahara auto. Thanks everyone for your imput. Oh, the thermostat didn't have an air hole nor a side that said UP like the factory one. Both sides were identical if that helps any.
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Old 05-26-2012, 08:59 PM   #15
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Like Jerry said in his post, check the radiator fins for mud blocking air flow as the previous owner could have been a mudder.

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Old 05-26-2012, 11:10 PM   #16
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i'll give that a look first thing in the a.m. thanks.
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Old 05-27-2012, 01:31 AM   #17
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You did install an 18 lb. radiator cap right? It needs to be an 18 lb. model so the coolant won't start boiling at a temp lower than it should.
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Old 05-27-2012, 01:41 PM   #18
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...edit...It stayed at 210 until last week when at highway speeds it creaped up to the red line and just as fast would drop back to 210. ...edit...

My Jeep was doing the exact same thing once it started warming up here in Arizona. I also bought the Jeep in the winter with no problems. The jeep would do fine at slower speed and even do fine off roading in the heat. At highway speed it would creep up above 210 (a little less than halfway to red) then instantly go to red and I would slow down and the temp would go down rather quickly back to above 210.

I have replaced everything in my cooling system (including a new 195F thermostat). The last thing I replaced was my radiator and that was the problem. The phenomena of instantly going red on temp at highway speed was my lower radiator hose collapsing causing the water pump to lose suction and cavitate which means no pumping of water was occurring. I thought I had a weak hose or was missing a spring (lol) inside of it. That was a wild goose chase. The old radiator was plugged up and my new water pump couldn't get enough suction flow due to the restriction in the radiator and only showed up as a problem at high rpm (highway speed).

Recommend you replace the thermostat with a new 195F one (cheap, easy and rules out a potential problem), flush the radiator or get a new one (super easy to replace). Get a brand new 18 lb. radiator cap from autozone (cheap, easy and rules out a potential problem)
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Old 05-27-2012, 03:07 PM   #19
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Get a brand new 18 lb. radiator cap from autozone (cheap, easy and rules out a potential problem)
Brand new, yes but not from autozone, radiator caps are so affordable that you want to either get an OEM or a Stant cap, don't settle for less.

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Old 05-27-2012, 04:00 PM   #20
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I put a stant 18lb cap on and replaced the fan clutch. I took it out for a test drive and seemed to do well till i got 25 miles from home and instantly got so hot i shut it down and waited a few min before trying to crank it. The engine sounded bad so i shut it down fast and called the ole AAA to get me home. Needless to say i saw about 18 jeeps go by me all riding with the tops off. Well after reading M1arks situation i don't know whether to go with the water pump and replace my hoses or jut order a new radiator. I had it flushed at the dealership yesterday so i would have thought they would know if it was clogged up or not? Got to wait on this to cool before anything. Any Ideas anyone?
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Old 05-27-2012, 04:01 PM   #21
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oh, on the 1 to 10 scale for a novice what is the waterpump replacement on it. I did ok on the Tstat and fan clutch.
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Old 05-27-2012, 04:24 PM   #22
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My recommendation is that you pressure test your system before you do anything else. At what elevation are you driving?
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Old 05-27-2012, 07:15 PM   #23
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?..edit...M1arks situation i don't know whether to go with the water pump and replace my hoses or jut order a new radiator. I had it flushed at the dealership yesterday so i would have thought they would know if it was clogged up or not? Got to wait on this to cool before anything. Any Ideas anyone?
Your symptoms are that the water pump is losing suction. Remove your lower radiator hose and look into the radiator. You might see what your problem is. Don't look into the radiator cap... It won't tell you much.
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Old 05-27-2012, 07:28 PM   #24
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oh, on the 1 to 10 scale for a novice what is the waterpump replacement on it. I did ok on the Tstat and fan clutch.
It's a good job for a less experienced mechanic who is at least comfortable wrenching and isn't afraid to start removing stuff and get dirty. For my 64 year old bones, it's a back breaker for me to replace because I have to get up over the top of the radiator of my TJ with its 35" tires and 5" of lift. For anyone else, it's not difficult at all.

I put the following suggestion that will help with the job out by itself for emphasis.

When you get the old water pump off, TAKE YOUR TIME and get every last shard/scrap/iota/spec/atom of the old gasket off the block where the water pump mounts. I mean every last atom of the old gasket needs to be removed or you'll end up with a leak when you mount the new water pump and gasket. Hang a bright light over where the water pump mounts so you can make sure that gasket mounting surface is clean enough for your heart surgeon to lay his scalpel and not worry about it getting dirty. Once you have gotten every last piece off you can see, then use a small fine wire brush on the surface and then wipe it off with a towel. By then, it should be ready to mount the new paper gasket and water pump.

Trust me that if you don't do as suggested above, you'll be kicking yourself afterwards when the non-pristine gasket surface doesn't seal against the gasket well enough and you get a big leak.

Ask me how I learned this many years ago.

Oh, tighten the water pump bolts with a 3/8" drive ratchet wrench. It's too easy to overtighten that size bolt with a 1/2" drive ratchet wrench. Also note that there are different lengths of bolts with one extra long bolt that can only go back where it came. Wire brush the threads of those bolts before reinstalling them, they will probably be rusty or slightly corroded. When tightening the water pump bolts, they are tightened to something like 32 ft-lbs. but if you don't have a torque wrench, that just means "good and tight" with your 3/8" drive wrench.
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Old 05-27-2012, 08:42 PM   #25
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To add to Jerry's post, one thing you can do is overtighten the thermostat housing bolts. This will crack the cast iron housing. I did that on my first one and there is no fix other than replacement.
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Old 09-15-2012, 10:46 AM   #26
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I always use a fail safe thermostat. they cost a couple bucks more but if you have a over heating problem and the fail safe kicks in it makes the thermostat stick in the open position so the fluid can still flow and cool the engine unlike the factory or cheaper ones that stay closed when they fail and cause the engine to over heat leaving you stranded
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Old 09-15-2012, 10:50 AM   #27
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Over the years, I've noticed so-called "fail safe" thermostats don't always work according to their theory of always failing in the open position. I stopped recommending them years ago, they just don't seem to be as reliable as a good conventional brand-name thermostat like Stant or Robertshaw.
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Old 09-15-2012, 11:20 AM   #28
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Over the years, I've noticed so-called "fail safe" thermostats don't always work according to their theory of always failing in the open position. I stopped recommending them years ago, they just don't seem to be as reliable as a good conventional brand-name thermostat like Stant or Robertshaw.
In the 30 plus years of jeeping ,racing and aerospace that I have been in I have never had a issue with the fail safe brand thermostat not working as they should and as a experimental aircraft pilot I need to have nothing but the safest equipment I can
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Old 09-15-2012, 11:22 AM   #29
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As a pilot myself Scott who has flown Experimental class aircraft, what does that have to do with the subject of cooling system thermostats? I doubt any of the aircraft you are flying has any need for a thermostat since aircraft engines are generally air cooled.
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Old 09-15-2012, 12:35 PM   #30
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I doubt any of the aircraft you are flying has any need for a thermostat since aircraft engines are generally air cooled.
Plenty of reciprocating aircraft engines have thermostats.

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In the 30 plus years of jeeping ,racing and aerospace that I have been in I have never had a issue with the fail safe brand thermostat not working as they should and as a experimental aircraft pilot I need to have nothing but the safest equipment I can
How many aircraft have you encountered with fail-safe thermostats?

The whole concept of the fail-safe thermostat is significantly flawed. Just having "safe" in the name doesn't make it so.

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