What are your coolant temps?

[rc51kid]

185-195 idle or traffic all day. but gets warm at highway speed up long gradual hills. 215 or more some times. the temp drops like a rock when i get going down hill. i would love to figure this out. everything is new oem except water pump and a few year old koyo (sp) rad. clutch is black with 10,000 in it. i drained it and filled the one side until it wont hold any more oil. Is that right? i also have 8" hellas mounted on a TJM bumper but just dont think that should make it run that hot. the worst i saw was 75mph with ac on in 85 deg temp long low up hills in kansas. i think it was over 220 before i turned on the heat.

 

[greentruck]

Adam,
Do this...

Stock OEM blue fan clutch seems to be pretty whimsy for the southwest climates. Many of us upgrade the silicone fluid in them to 20,000 - 30,000 cst fluid for superior cooling results. Many threads on the subject . John

Between altitude and heat in Utah, the air is thin and hot. The stock fan clutch runs its off, but can't quite keep up.

94SRUNNER's suggestion to make sure there's no air in the system could also help. A common culprit is an air blockage due to the long rear heat lines.

BTW, our truck is running in the 190-201 F range right now with temps in the higher 80s.

 

[FXJ 96]

I have had my truck for a year now, 233K miles on the odometer, but just took my first longish trip in it this past weekend. Put almost 700 miles on her and much of it was on 75 MPH highway, also spent a couple hours creeping at 15 MPH on a beach. Because of this thread I left the Scangauge hooked up the entire time and noticed coolant temps 185-197 over the trip. I'd say 90% of the time is was 188-193 and tended to stay 190-193 when going 80 MPH with A/C full blast and outside temps around 80-90. Intake air measured around 130 on the highway. I have a ARB front bumper, winch, and a couple largish lights which block some airflow but it seems to stay in the range most here have described. I was also fairly loaded with family of five and gear for the beach weekend, and I have 35" tires, but she just chugged along and seemed happy.

 

[Onefastrx7turbo]

Unless it's super hot outside, my coolant sits at 179F. Recently with the AC on and driving around town i'll see 182-188F. Prolonged idling or extended slow speed I have seen 190F. The only time it goes over 190 is climbing hills. Ive seen 210 climbing the hills in 100F degree heat.

 

[rockstate45]

Unless it's super hot outside, my coolant sits at 179F. Recently with the AC on and driving around town i'll see 182-188F. Prolonged idling or extended slow speed I have seen 190F. The only time it goes over 190 is climbing hills. Ive seen 210 climbing the hills in 100F degree heat.

What type of cooling maintenance has your rig seen?? Those are some pretty good numbers.

Open question for anybody here: What exactly is "operating temperature" on our rigs?

 

[Onefastrx7turbo]

New belts, WP, T-stat and fan clutch mod. I'm running the factory radiator and about 80/20 distilled water to Toyota red.

 

[120mm]

Never seen really radical heat, but using a Torque II, mine either sits at 186 or 193.

186 if it's cool temps and no load and 193 if over 80 F and/or climbing hills.

 

[zapatius]

Replaced leaking stock radiator with aluminum Koyorad. Replaced original fan clutch with new blue fan clutch. Replaced all hoses, Toyota red coolant, Toyota thermostat, Denso waterpump, new Goodyear belts, Denso A/C drier, Denso condenser and installed a Koso digital temp gauge running off upper coolant hose.

With A/C off in 95 degrees/90% humidity, running 185-189 in city or highway at 70 mph.

With A/C on in 95 degrees/90% humidity, runs 192-197 in city, 187-192 on highway at 70 mph.

I live at 600 feet above sea level. I run a Thule roof rack but not towing anything.

 

[FXJ 96]

Is cooler always better? Based on an earlier post from 2011, it was said that having monitored many 80's with scan gauges they all seem to settle in around 190 degrees. If designed to run at 190, is 180 better? 170? Or is running at the temp the designers intended better? Does it affect performance, mpg, to run at different temps - either high or low?

 

[BILT4ME]

No, cooler is not always better. @scottryana can give the exact numbers, but when an engine is cold, it is in "open loop" mode and the computer holds the injectors open linger, dumping in more fuel (just like the automatic choke of yesteryear) and when it warms up, the computer goes into "closed loop" mode, and the fuel is not held on as long, thus, reducing the fuel consumption.

If an engine is cold, it uses more fuel than when it is warm.

When an engine gets too hot, is has other issues with pinging, overheating, and (on carbureted engines, vapor lock) the air conditioning cutting out due to overheating, and eventually cooking the engine to the point of lock-up due to thermal expansion.

These are designed to operate in a "sweet spot" of temperature. The T-Stat should start to open about 180*F and be fully open at 195*f. So, closed loop is probably about 180*F.

Run an engine without a thermostat and it will always run cold and have poor efficiency.

 

[Tools R Us]

...
Open question for anybody here: What exactly is "operating temperature" on our rigs?

How long is a piece of string? Kind of a difficult question to answer and widely debated. Most engines from the era are designed to run in the 190-220F ish range, my guess, the 1FZ is about the same.

The 3FE and 1FZ are both bypass systems. When cool all of the coolant bypasses the radiator goes directly back to the water pump. As they warm, it is mixed. When fully hot, the bypass is closed and all of the coolant goes through the radiator. The 3FE is an upper/output thermostat system, the 1FZ is a lower/input system.

Some clues for the 1FZ: The thermostat starts to open at 176-183F, the spec for fully open, bypass fully closed is 203F. These are specs for the coolant entering the engine, the coolant sensors are in the head. Before getting to the sensor, the coolant will travel through the block, oil cooler, head, etc, absorbing heat (doing it's job). So, the amount of absorbed heat will depend on loads, conditions, etc. Depending on loads, the operating temp as seen by the sensors will be significantly higher than intake/thermostat.

 

[greentruck]

SNIP

The 3FE and 1FZ are both bypass systems. When cool all of the coolant bypasses the radiator goes directly back to the water pump. As they warm, it is mixed. When fully hot, the bypass is closed and all of the coolant goes through the radiator. The 3FE is an upper/output thermostat system, the 1FZ is a lower/input system.

Some clues for the 1FZ: The thermostat starts to open at 176-183F, the spec for fully open, bypass fully closed is 203F. These are specs for the coolant entering the engine, the coolant sensors are in the head. Before getting to the sensor, the coolant will travel through the block, oil cooler, head, etc, absorbing heat (doing it's job). So, the amount of absorbed heat will depend on loads, conditions, etc. Depending on loads, the operating temp as seen by the sensors will be significantly higher than intake/thermostat.

Thanks for stating that so clearly, Tools.

I think the fact that the temp sensor sends higher temps than the block actually sees is part of why the stock water temp gauge is neutered. They don't want people panicking when they see that needle climb, because the engine won't actually see that high a temp for the most part, as it's the output after picking up all the heat and before it's shed in the radiator and cooled for its next journey back through the engine.

I must admit, even now, several years after doing the temp gauge mod, every once in awhile I'll look down and panic over one of those brief spikes, before I realize everything's cool

 

[Tools R Us]

Mine ran ~190F ish on the way in this morning, the humidity is coming up so, easier to cool. Relatively useless trivia.

 

[baggar11]

1994 Cruiser here w/ 203k miles

Silla 2 row 2 inch aluminum radiator
black hub fan clutch set @ 95F opening w/ 7k cst silicon
toyota pump and thermostat
70/30 water/coolant ratio

95-100F ambient temps produce the following w/ AC on
187-190F coolant temps idling
183-187F coolant temps stop and go traffic
176-180F coolant temps constant movement, ie: 25+mph to highway cruise speeds

All temps read from a koso gauge installed in between engine block(outlet) and radiator(top inlet).

 

[Dave 2000]

I think the fact that the temp sensor sends higher temps than the block actually sees is part of why the stock water temp gauge is neutered. They don't want people panicking when they see that needle climb, because the engine won't actually see that high a temp for the most part, as it's the output after picking up all the heat and before it's shed in the radiator and cooled for its next journey back through the engine.

If you look here https://forum.ih8mud.com/threads/my-lc-80-thread.365673/page-13, post # 243, I have come to the same conclusion, I have also thrown in some factual numbers.

regards

Dave

 

[greentruck]

Dave,
Whoa, yeah, lots of data. Will keep this in mind if I ever feel the need to add an electric fan. Using the blank shift indication panel on the manual truck dash for the fan op indicators was brilliant

 

[NLXTACY]

97 4.6 SC LX with 315s and 105-110º ambient BEFORE @lantanks 's Orange Hub mod I thought I was doing ok. I fixed a LOT on my truck but still saw my temps spike up into 210º territory every now and then.

Same truck AFTER LT's orange hub mod and after doing a 700 mile round trip this past weekend with MANY miles of hill climbs including the 180 in and out of Sequoia plus the Grapevine and Buck Rock Jeep trail and my temps never got over 193º. Of course I scored a PO302 and then my temps went up another 10º but even still. Grapevine at 193º is UNHEARD of.

 

[Dave 2000]

Dave,
Whoa, yeah, lots of data. Will keep this in mind if I ever feel the need to add an electric fan. Using the blank shift indication panel on the manual truck dash for the fan op indicators was brilliant

Thanks for that, I expect the new LED's any time now, soon as it is installed I will post up a pick.

regards

Dave