Coolant Temp, what's the maximum, 2UZ-FE VVT-i (1 Viewer)

[NoTempoLimit]

I recently took a road trip that included the desert areas of SE California and West Arizona. I saw ambient temps between 105 and 117ºF [40.5 to 47.2ºC]. My engine coolant temp (viewed on ScanGage) varied up to 204ºF [95.5ºC] under high load (climbing, AC on). Under lower loads (descending) the engine temp would settle at around 193ºF [89.4ºC]. I was not towing and have no external accessories. Speeds were flow of traffic for interstate highway. I sometimes slowed and joined the semi's on the right when my temps got above 200ºF.

I know ECU map controlled thermostats vary the temperature. Does anyone know the correct upper limit for coolant temp for the 2UZ-FE? I have the VVT-i version. I searched this forum with no result.

I checked coolant level (absolute) and mixture (checked with refractometer, coolant was slightly over 50% mix). My LC has 180k miles and is coming due for timing belt, so if I need to have any cooling system work done, now is the time.

Thanks!

 

[2001LC]

In summer heat, the 06-07 VVT, ECT (engine coolant temp) runs at 194F to 197F. They will go over 197F to ~200F, usually for only a few moments. Then fan clutch locks up to increasing air flow through radiator fins and ECT drops back down. I've only run test at 103f OATs max in full 3PM sun driving on blacktop.

Thermostat is controlled by temperature of coolant. It's not connected to electronics. Although ECU does use/read ECT, using info for a number functions.

Classic sign of clogged Radiator fins. Stop a a red light, in summer heat and sun, A/C on. ECT jumps over 200F, than drops as we drive.

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

forum.ih8mud.com

 

[NoTempoLimit]

Thanks @2001LC you confirmed my suspicions. Yes the 95ºC temp spikes were brief. Yes rear AC was on, forgot to mention that. I'm at 182k mi. If no debris is found, perhaps its time for a radiator replacement?

 

[NoTempoLimit]

In summer heat, the 06-07 VVT, ECT (engine coolant temp) runs at 194F to 197F. They will go over 197F to ~200F, usually for only a few moments. Then fan clutch locks up to increasing air flow through radiator fins and ECT drops back down. I've only run test at 103f OATs max in full 3PM sun driving on blacktop.

Thermostat is controlled by temperature of coolant. It's not connected to electronics. Although ECU does use/read ECT, using info for a number functions.

I should have been more clear: I saw ECT of 202 - 204ºF briefly WHILE at highway speed. I don't see how the fan clutch could have made a difference. It should have been freewheeling.

 

[2001LC]

As heat raises, radiator shed more heat on coil of fan clutch (FC). Coil expands open valves inside fan clutch. This locks fan increases resistance within FC.

FC does not "free wheel". It has more of less resistance, in response to its coils temp. The higher the heat the more resistance (locking fan as if solid drive).

As I said. I've not tested ECT with OATs at above 103F OAT. At 117F OAT, 204F ECT may be normal.

Many youtubes on checking FC. Timmy has a good one.

Inspect radiator fins and washing them, is simple. See link I posted above.

Note the coil on FC.

 

[NoTempoLimit]

@2001 Thanks, did not know about the coil. I was thinking old-school that it was just a clutch. I wondered why it was so big. Perhaps it’s time to change it out at 182k mi?
BTW I still remember the 1976 Ford Maverick my dad had. It was so basic it had NO fan clutch at all. Fan was just bolted to the front of the engine and made a ton of noise.

 

[2001LC]

FC is to reduce drag on crankshaft, when max cooling is not needed. Saving horsepower, thus increasing MPG.

You'll hear fan roar loudly on cold start-up, first ~90 seconds. Until oil inside moves to reduce resistance of FC. Then again, as ECT gets above optimal operating temp to increase cooling (air flow over radiator fins & pipes).

Old school solid fan, were direct drive. Most attached to water pump, driven by fan belt. Those took more HP at all times/temp. When gas was $0.25/gallon and OPEC didn't have us over-a-barrel.