I see no reason to! OEM is what systems is designed for. We go down a rabbit hole, as we deviate from stock.
2UZ-FE Normal Operating Temperature
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What year do you have?
Although we run above thermostat base temp. Running over 195F is running hot.
OEM Thermostat is 82C (179.6F)
The guy was wrong about the thermostat, but the other part about asking a toyota tech, there is merit in that.
There is a range of temps that are normal.
There is deviation in the coolant temp sender.
There are 7 degrees of variance in the thermostat opening.
There is a number of some degrees of variance in the valve lift at 203 degrees. Only a specified opening of 10mm of travel at 203 degrees. IT could be less travel at 203 degrees, which is bad, or more than 10mm of travel at 203 degrees, which is good. It also needs to close at 104 degrees.
The fsm does not state a normal operating coolant temp. (that I know of) You can only infer from the opening and closing of the thermostat that it is related to normal coolant temp operating range.
You can take into account the AC compressor shut down temp and the idiot lights turn on characteristics on the combo meter.
Changes over facelift years- exhaust and intake designs, evap systems etc will all affect coolant temp, and oil temp. They have changed to higher and higher temps over the decades.
New part change outs may keep coolant temps lower to a level that YOU think is correct. Educate yourself.
Chase whatever temp you like but if it's in the operating range of the thermostat, and a certain amount above and below, it's normal.
Don't rely on my opinion, do your homework.
There is a range of temps that are normal.
There is deviation in the coolant temp sender.
There are 7 degrees of variance in the thermostat opening.
There is a number of some degrees of variance in the valve lift at 203 degrees. Only a specified opening of 10mm of travel at 203 degrees. IT could be less travel at 203 degrees, which is bad, or more than 10mm of travel at 203 degrees, which is good. It also needs to close at 104 degrees.
The fsm does not state a normal operating coolant temp. (that I know of) You can only infer from the opening and closing of the thermostat that it is related to normal coolant temp operating range.
You can take into account the AC compressor shut down temp and the idiot lights turn on characteristics on the combo meter.
Changes over facelift years- exhaust and intake designs, evap systems etc will all affect coolant temp, and oil temp. They have changed to higher and higher temps over the decades.
New part change outs may keep coolant temps lower to a level that YOU think is correct. Educate yourself.
Chase whatever temp you like but if it's in the operating range of the thermostat, and a certain amount above and below, it's normal.
Don't rely on my opinion, do your homework.
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Is there any reason to replace the Coolant temperature sensor as part of PM? I was trying to link a thread where a guy replaced because a code was thrown and his old one looked really bad.
I'll add: Whereas deviating from stock design, is a rabbit hole best to avoid. That is, in a pure stock rig.
That said:
In a build rig we should be able to get temps back factory normal. Or rather engine running at factory spec. But with added weight, large mass of metal absorbing than radiating heat and blocking air flow. Some mods may be called for, in certain parts of the globe.
@gungriffin does have a lower temp thermostat. His TRD package requires it apparently. He has a heavy built rig, and has stated he's not seen the boil fuel issue. He runs his rig all over Colorado in all season.
This is further andodate evidence that engine heat is our primary cause of fuel boiling. Fuel blend is secondary. Failure of EVAP component, is last and should give us a DTC (code).
Testing the ECT sending unit is a good idea. The FSM does have a procedure for this. But a simple test, although can be misleading. Is to shoot a temp gun near the sending unit. Compare that to ECT tech stream read out. I shoot my IR temp gun, just downstream of thermostat. I also try to shoot on front water by joint near sending unit. I'm usually with a few degrees of tech stream reading.
Yeah I've been looking for what factory consider normal operating temp range. I do suspect we've variation in the years and milage of engine. But I'm sure hitting 197F or higher in normal driving, is indication of system issues that needs correcting. 06-07 I've biggest question on as to what is "normal" from factory. But I do have logs indicating that 187F (high I hit) is baseline in the 06-07. That with full metal skids and belly pan, the temps jump up to ~192F average (w/o heavy bumpers). That was Merlot 07LC w/63K miles. In it, I did hit in the 201F when I ran it up (high RPM run) w/bellypan, trying to heat CATS. So was not a good ECT test. It also was without doing a full coolant system service. But just driving around with the full metal skids and belly pan, it did run hotter.
Lately I've been looking more 98-02. Which I see consistently 184 to 187 F in well turned engine. The two I'm looking at currently, are high mileage. With high mileage comes wear. So they are looser running engine presumable. I suppose that would likely mean less friction and as such low temps may by a few degrees.
Today I'll be running short term logs on a heavy 05LC, no bell pan or #1 or #2 skids on. I just serviced coolant system. Engine seem okay no apparent vacuum leaks, with report newer spark plugs. Does have some unusually wiring. One wire is tap into #1 coil??. Some fuel injector wires have been spliced. Seem to run okay. It's actually a Tundra long block in it, of unknown year and mileage. I did find it had non OEM thermostat and rad cap. It was running cool ( no boiling issues) ~187F. I'll report back on its temps.
One more factor, to be fair to the discussion, is that my fuel tank is aftermarket too. It is aluminum and sticks down another inch or two into the under body airflow. The bottom of the tank is also thick enough that it has been used as a skid plate once or twice (or more...).
I just can't agree that a vvti 100 running at 197 degrees needs correcting. Even less that a normal operating coolant temp is 187 for a vvti.
It's all good though, there's no harm in buying parts. There's nothing more I could replace on mine chasing a lower than 194.7 techstream temp.
The definition of normal is not defined.
It's all good though, there's no harm in buying parts. There's nothing more I could replace on mine chasing a lower than 194.7 techstream temp.
The definition of normal is not defined.
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I love that episode and I've been thinking about it everyday since I got the lx!
So I just thought I'd update anyone who was following my search of lowering my temps. Did a 2000 mile roundtrip, AC on, outside temps between 78-98. Cruising at GPS 78 mph, temps fluctuated from a low of 195 to 203. Couple traffic times, temps went as high as 205. Stayed in that range well. This seems OK? Although many people report temps of 185-190 cruising. Not sure why. New stat I put in was a 82C.
For a 99 that is definitely running hot.
ECT 184-187f (98-02)
I just did a short 15 mile city asphalt st and concrete HWY OAT 97-98 Sunny 3PM in mile high city hot and dry. IAT running 106 to 115f. ECT 184-187f, A/C off. Touched on 189f for 3 seconds then back down to 187F, while parked and idling to email the log data.
I've logged a few well tuned pure stock w/coolant systems serviced 98-02. They're consistently run 184-187 A/C off. A/C on, 1-2 f higher if that.
ECT 187-190 (05LC heavy), A/C on 190-194F.
05LC w224K miles. Log yesterday after coolant system service (old fan clutch). Had to double wash radiators and still could see crud around edges. No belly pan of skids. Steel bumpers, winch, tire rack swing, ladder, rack, sildders, OME lifted. Tundra engine of unknow miles in 100 series.
Had a local mud guy stop by, friday evening, with his 03LC w276K mile heavy. Said temps normal. I ask what he was seeing. He said: "197 to 212F" IIRC. That is not normal op temp, I said. I looked under his hood, of a very sharp looking build rig w/Tesla screen & scan gauge.
In 1 minute I spotted: ECT 198F idling at sundown for 20 minutes, OAT ~82F.
1) coolant reservoir empty.
2) older looking radiator cap
3) clogged radiator fins and possible leak.
4) Brake fluid over filled.
5) Air filter very dirty and seal curled over, allowing dust in intake (very common).
I see this stuff day in a day out. High 190 and low 200F is not normal OP Temp when in factory spec. NOT!
In 1 minute I spotted: ECT 198F idling at sundown for 20 minutes, OAT ~82F.
1) coolant reservoir empty.
2) older looking radiator cap
3) clogged radiator fins and possible leak.
4) Brake fluid over filled.
5) Air filter very dirty and seal curled over, allowing dust in intake (very common).
I see this stuff day in a day out. High 190 and low 200F is not normal OP Temp when in factory spec. NOT!
shtbrwn86
SILVER Star
In an earlier post I shared that during my 600 miles road trip where OAT temps ranged from 95-100 I only ever saw 203 when doing 75 uphill over a pass, and even then it was a blip. In those scenarios it tended to average 195-199.
Cruising at high altitude, same outside temps but no hill climbing I was seeing between 192 and 195. Normal temps for me in sub-90 degrees are 185-188 pretty much all the time.
The only thing left to do that I can think of is to add foam to the radiator assembly and replace the thermostat. Will be tackling that soon. I'm hoping that gets my temps down a bit more, but I live in Western Washington where it's hard to do any extreme temp testing.
Not knowing your year, stock or built. Makes difficult to say if that is what your best ECT can get down to. Adding that info to the signture line would be helpful.
If all stock, that's on the high side for 98-02.
With steel bumpers and winch OAT 95-100. The 192-195f ECT with A/C on, sounds about right, but on high side.
There may be more you can do. Like washing the condenser and transmission oil cooler radiators, tune up, transmission flush. I'll assume that is a new fan clutch, based on statement "only thing left to do".
I did some wheelin today ambient temp
A new radiator cap seemed to help me. I did not have an oem one on there (no Japanese characters) but it was 1.1 bar.
Well I'm not sure what more to do. Here's a refresh what I've done.
- New OEM fan clutch
- New OEM thermostat
- Radiator about 3 years old - Not OEM and doesn't have foam.
- All radiators washed very well.
- Over the last two years, the trans fluid has been changed about 6 times from the sump.
- Coolant was changed a year ago with Toyota Red.
- Rad cap is not OEM and has a 0.9 BAR, but cap pressure doesn't effect running temps. It changes your boiling temp.
- Coolant system bled with method suggested in this thread. This lowered temps 3-5 degrees from initially fitting Stat.
- TB and WP done at 224k. 240k miles currently on truck.
Advice on where to go from here?
- New OEM fan clutch
- New OEM thermostat
- Radiator about 3 years old - Not OEM and doesn't have foam.
- All radiators washed very well.
- Over the last two years, the trans fluid has been changed about 6 times from the sump.
- Coolant was changed a year ago with Toyota Red.
- Rad cap is not OEM and has a 0.9 BAR, but cap pressure doesn't effect running temps. It changes your boiling temp.
- Coolant system bled with method suggested in this thread. This lowered temps 3-5 degrees from initially fitting Stat.
- TB and WP done at 224k. 240k miles currently on truck.
Advice on where to go from here?
I agree, should not affect ECT. Provided it allowing proper flow of coolant in and out of reservoir. But recheck level under cap periodically, after 8 hour cool down, with heaters set to hot the drive before cool down. The check needs to be when cool OAT in the morning out of the sun, and with front higher than rear of vehicle, to get best results.
What I have found with non OEM caps. They do not fit as tight. That when I pressurizing system for test or to blow out during a flush, with ~10PSI into rad through reservoir hose. I'll see and hear leakage out of non OEM caps.
Once coolant system to spec. Which includes the foam arounds side and top of radiator (lower foam seems to have less effect). Tune engine and make sure no vacuum leaks and PCV valve working. Also run a fuel system cleaner through the gas. I like 44k and or Chevron Techron (at different times). I also have been using IK20TT denso spark plugs. Don't have any comparison to non TT, but may drop cylinder head temp a tad, but IDK.
Watch fuel trims too see if running lean.
I just learned from @abuck99. That the coil on front of fan clutch, even new OEM. Are reportedly varying from one to another.
What I have found with non OEM caps. They do not fit as tight. That when I pressurizing system for test or to blow out during a flush, with ~10PSI into rad through reservoir hose. I'll see and hear leakage out of non OEM caps.
Once coolant system to spec. Which includes the foam arounds side and top of radiator (lower foam seems to have less effect). Tune engine and make sure no vacuum leaks and PCV valve working. Also run a fuel system cleaner through the gas. I like 44k and or Chevron Techron (at different times). I also have been using IK20TT denso spark plugs. Don't have any comparison to non TT, but may drop cylinder head temp a tad, but IDK.
Watch fuel trims too see if running lean.
I just learned from @abuck99. That the coil on front of fan clutch, even new OEM. Are reportedly varying from one to another.
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I just learned from @abuck99. That the coil on front of fan clutch, even new OEM. Are reportedly varying from one to another.
To clarify, not exactly the spring varying from one to another but the set temperature the internal valve responds (opens). On our blue AISIN fan clutch this setting is adjustable.
As the bi-metal temperature sensing spring heats up from hot airflow coming across/through radiator, the spring responds and expands which is connected to and opens a valve inside the clutch to allow the fluid to flow from and back to the reservoir. Technically speaking, the variance could either be the spring itself: maybe material differences, or how its wound and affixed to the outside of the clutch but mainly it's been the position the valve is set to open in relation to the temperature- which proportions the fluid to flow to the drive mechanism inside the clutch.
Over on the 80 series forum there has been considerable thread discussion, experimentation, and confirmed success with modification on the AISIN blue FC. Summing up the findings: there is a wide variance in valve opening temperature among the same part number of (blue) FC. Anywhere from 10F to 30F+ degrees variance = engine runs hotter until fan fully engages vs engaging at lower running temps. Also lot of experimentation with the clutch fluid viscosity. Stock fan clutch comes with a minimal amount of silicone fluid its "just" enough to work while maintaining optimal fuel efficiency (but it's not optimal for trail use). IDK the stock fluid viscosity; reportedly its 4,000 (4K) Cst Silicone Fluid. Adding a higher viscosity fluid such as 15k or 20k+ CST, impacts engagement, reducing slip which moves more air. The biggest benefit I've found is lower trans temps on trail and more stable ECT.
Another issue with the life cycle and optimal operation of the FC is age/miles and environment. A rusted temp sensing spring ( rust belt trucks) may not respond as well as a new spring- that impacts cooling. Also the fluid breaks down at a certain point; 150k 200k? IDK. This is what causes the fan slip more- which impacts cooling. If the bearing on your fan clutch is in good shape, and the temp sensing spring is in good shape, you can refurb your FC with fresh fluid and check or adjust the opening temperature.
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Mine seems to operate fully (when I hear the roar) at around 195. However, when driving on the highway, isn't the fan redundant due to the natural increased airflow? If pulling hard up a mountain pass towing, it may then be needed. This is how my diesel landcruiser has behaved.