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Unread 05-08-2013, 08:01 PM   #1
herqulees
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I can't really make sense of the thermostat temp argument

Their is nothing wrong with my Jeeps cooling system, I'm just curious as to what the pro's and con's are of cooler thermostats. I bought my Jeep with a water pump that had literally shattered to pieces. So I got a new water pump, new hoses, and a new 180F thermostat, because I don't like the idea of any engine reaching, let alone exceeding, 200F, that's just insane to me, and I see it as a "buffer"; the cooling system can start working at full capacity before the engine starts exceeding its designed 195-210F.
I would of bought a 160F but that was too cold IMO for it to run safe internal engine clearances and I wasn't aware of how the computer controlled open and closed loop as far as engine temp.
Now that I've had my Jeep hooked up to a computer I've seen it's the usual computer, it could care less what the engine temp is as long as the O2 heaters are working it'll switch to closed loop by the time the engine is 120F, if not before. My Jeep has gone through thousands and thousands of miles since I bought it and the only time it touches 200+F is a hot day with the A/C on while idling or in traffic, the rest of the time it runs at 180-190F, my fuel mileage ranges from 15 to 20mpg, from hauling engines in the back around town to cruising on the interstate nonstop from full to empty at 70-80mph, respectively.

So. Can someone explain what is bad about my 180F thermostat? I just can't figure out what all this talk is about non-stock temp thermostats being bad.

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Unread 05-08-2013, 08:47 PM   #2
KoreaZJ
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Bought my ZJ new in 2/94. After the original water pump went out, am on my second FlowKooler pump. Each time, have installed a Robert Shaw 180 stat to reduce operating temperatures. Only difference is it runs cooler, still plenty of heat during cold winters. Highway mileage is 20+ mpg.
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Unread 05-08-2013, 08:55 PM   #3
PolkaPower
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I put the 180* in and it got too cool this last winter. It's perfect now though. I have my trans bypassed too so that made the motor cooler to begin with.
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Unread 05-08-2013, 08:58 PM   #4
herqulees
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Quote:
Originally Posted by PolkaPower View Post
I put the 180* in and it got too cool this last winter. It's perfect now though. I have my trans bypassed too so that made the motor cooler to begin with.
I haven't had any issues reaching operating temp in winter, though it is noticeably slow for the last ten or so degrees it warms up, but the heater starts blowing semi-warm just as the temp gauge starts to touch 100F.
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Unread 05-08-2013, 10:12 PM   #5
zander21510
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I have the stock 195 with the rest of my cooling system in great shape, warms up to 190ish during winter, have yet to see it during summer but its always been around 210.

Before it had a 185 thermostat in it that broke, stuck partially open I think. It wouldn't warm up past 160 in the cold days, and my MPG suffered.

I think its just that its designed to run at 210, you should only go with a lower temp thermostat if everything else is fine and you need it to achieve the nominal 210.
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Unread 05-08-2013, 11:50 PM   #6
5-90
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Much depends on the control system.

OBD-II? I don't recommend going away from OEM-spec. You are very likely to get a code and a persistent CEL/MIL
OBD-I? You can probably go down a step, but you may get a code
Pre-OBD? You have leeway. I've had five RENIX rigs (all pre-OBD, obviously,) and I've been able to do the following:
- OEM 195* thermostat: used with Water Wetter, coolilng flush & fill every two years, held right about 200-205*F operating temp out of traffic.
- Cooler 180* thermostat: as above, held an op temp of 195* or so (earlier coolant flow kept op temps down.)
- Coolest 160* thermostat: as experiment. Conditions and operation similar to that for 180* thermostat.
- No thermostat: My 88 is one of three vehicles I've had that simply did not tolerate a thermostat in place. Would overheat within five minutes of running. (Other two vehicles were 1985 Cavalier V6-173 and 1980 Honda Accord 4-1800CVCC.) Water wetter, cooling maintenance, &c as above, plus installation of copper heater lines (got tired of buying moulded hoses every time,) and operating temperature may as well be fixed at 190*F; rain, snow, s**t, or mud.)

I honestly don't think that an operating temperature of 210-215*F is any good for the engine - and, it's too hot for the engine oil to do its job effectively. Depressing the operating temperature of the engine is possible - and, with RENIX, I think it's a good idea.

For those of you who would argue that it's necessary for emissions control, I've noted that depressing the operating temperature of the engine had no negative effect on tailpipe emissions, had a small net increase on fuel economy, and probably increased oil longevity (I never had a UOA test done.)
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Unread 05-09-2013, 05:24 AM   #7
Technohead
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Engine efficiency depends on the operating temperature. Too cold = less efficient. There is no reason to deviate from the factory configuration unless you are continuously operating in an extreme climate.
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Unread 05-09-2013, 05:49 AM   #8
herqulees
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Quote:
Originally Posted by 5-90 View Post
Much depends on the control system.

OBD-II? I don't recommend going away from OEM-spec. You are very likely to get a code and a persistent CEL/MIL
OBD-I? You can probably go down a step, but you may get a code
Pre-OBD? You have leeway. I've had five RENIX rigs (all pre-OBD, obviously,) and I've been able to do the following:
- OEM 195* thermostat: used with Water Wetter, coolilng flush & fill every two years, held right about 200-205*F operating temp out of traffic.
- Cooler 180* thermostat: as above, held an op temp of 195* or so (earlier coolant flow kept op temps down.)
- Coolest 160* thermostat: as experiment. Conditions and operation similar to that for 180* thermostat.
- No thermostat: My 88 is one of three vehicles I've had that simply did not tolerate a thermostat in place. Would overheat within five minutes of running. (Other two vehicles were 1985 Cavalier V6-173 and 1980 Honda Accord 4-1800CVCC.) Water wetter, cooling maintenance, &c as above, plus installation of copper heater lines (got tired of buying moulded hoses every time,) and operating temperature may as well be fixed at 190*F; rain, snow, s**t, or mud.)

I honestly don't think that an operating temperature of 210-215*F is any good for the engine - and, it's too hot for the engine oil to do its job effectively. Depressing the operating temperature of the engine is possible - and, with RENIX, I think it's a good idea.

For those of you who would argue that it's necessary for emissions control, I've noted that depressing the operating temperature of the engine had no negative effect on tailpipe emissions, had a small net increase on fuel economy, and probably increased oil longevity (I never had a UOA test done.)
Thanks for all the information, and am glad someone else agrees 200+F is too hot for oil to be reliable, that was another main reason I went with the cooler thermostat that I forgot to mention. And also glad someone else can agree that the cooler thermostat had little/no emissions and fuel efficiency issues.
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Unread 05-09-2013, 05:54 AM   #9
herqulees
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Quote:
Originally Posted by Technohead View Post
Engine efficiency depends on the operating temperature. Too cold = less efficient. There is no reason to deviate from the factory configuration unless you are continuously operating in an extreme climate.
But I haven't suffered any worse fuel economy or had issues with emissions, same as 5-90 said, the 180F thermostat doesn't change anything more than knocking 20 or so degrees off the engine temp, it's when you go down to the 160F and your engine actually starts running at ~170F and lower things won't be happy.
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Unread 05-09-2013, 07:52 AM   #10
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I'm running a 195* stat in my 5.2 and have yet to see it hit 210* on the temp gauge. Oddly enough, when I first bought it, the PO had the water pump replaced and a colder 180* stat installed, and during the winter it would sit just past 210*. I first replaced the temp sending unit and it read the same. My next maintenance was a full cooling system and heat core flush and replacement stat. I found the heater core plugged with stop leak, along with old coolant in the radiator and some corrosion on the radiator core.

After flushing the block, radiator and heater core, I filled with the newer Chrysler spec Zerex G-05 coolant, installed the OE spec 195* stat and now I consistently run well below 210*, and that's still with a questionable radiator. It should be interesting to see what happens this summer once I fix the AC and temps hit 95*+
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Unread 05-09-2013, 11:15 AM   #11
ratmonkey
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Uao's regularly indicate no thermal oil breakdown in jeeps running stock temperature thermostats. Contaminants are the usual reason to change oil and many well maintained jeeps can see oci's in the 7500-10000 range with the right filter before the oil sees any mechanical or heat break down.
Assuming a quality semi synthetic, synthetic, or blend is used.

There is absolutely no reason to deviate from stock equipment unless other modifications have been made.

Given enough time, most vehicles will reach designed operating temperatures no matter the thermostat installed.
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Unread 05-10-2013, 06:21 AM   #12
herqulees
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Quote:
Originally Posted by ratmonkey View Post
Uao's regularly indicate no thermal oil breakdown in jeeps running stock temperature thermostats. Contaminants are the usual reason to change oil and many well maintained jeeps can see oci's in the 7500-10000 range with the right filter before the oil sees any mechanical or heat break down.
Assuming a quality semi synthetic, synthetic, or blend is used.

There is absolutely no reason to deviate from stock equipment unless other modifications have been made.

Given enough time, most vehicles will reach designed operating temperatures no matter the thermostat installed.
But still the question is, why run such a high temp when it serves no (known and proven) purpose.
My Jeep is getting close to 20,000miles since I installed a 180F thermostat, and it is a very rare event for it to go over 190-195F. It uses no oil, it uses no coolant, I get no ECM codes, all readiness monitors pass without issue, the engine switches to closed loop before it's even warm enough to blow reasonably warm air through the heater, it averages 16-18MPG. It's a perfectly sound engine, so why should I have it run hotter?
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Unread 05-10-2013, 07:02 AM   #13
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Originally Posted by herqulees View Post
But still the question is, why run such a high temp when it serves no (known and proven) purpose.
My Jeep is getting close to 20,000miles since I installed a 180F thermostat, and it is a very rare event for it to go over 190-195F. It uses no oil, it uses no coolant, I get no ECM codes, all readiness monitors pass without issue, the engine switches to closed loop before it's even warm enough to blow reasonably warm air through the heater, it averages 16-18MPG. It's a perfectly sound engine, so why should I have it run hotter?
I think they run hotter than they need to because of emissions laws.
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Unread 05-10-2013, 02:15 PM   #14
ratmonkey
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almost every modern gas vehicle runs at 200-210 for emissions purposes. the computers are tuned to run well at this temperature. it's not too hot for the oil, it's not too hot for the coolant mix under proper pressure, and it's not too hot for mixed metal blocks/heads.

you have to be really outside the normal parameters on many sensors to throw a code. there's no reason to go out of your way to go hotter, just as there's no reason for anyone with a factory system to go out of their way to install a 180* stat. your vehicle doesn't have problems with it, but there have been people here that got codes and their jeeps wouldn't pass all emissions monitors.
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Unread 05-10-2013, 02:41 PM   #15
PolkaPower
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Quote:
Originally Posted by ratmonkey View Post
almost every modern gas vehicle runs at 200-210 for emissions purposes. the computers are tuned to run well at this temperature. it's not too hot for the oil, it's not too hot for the coolant mix under proper pressure, and it's not too hot for mixed metal blocks/heads.

you have to be really outside the normal parameters on many sensors to throw a code. there's no reason to go out of your way to go hotter, just as there's no reason for anyone with a factory system to go out of their way to install a 180* stat. your vehicle doesn't have problems with it, but there have been people here that got codes and their jeeps wouldn't pass all emissions monitors.
You get like 50 hp if you put a 180* stat in though.
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