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Thermostat Fan Switch 1MZ-FE


TommyM
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Hey guys, i'm not a complete noob but i'm actually curious about those that have actually owned 1MZ-FE powered vehicles. I've recently had an interesting thing pop up in my mind, so i figured i'd ask the community their opinion.

 

Right, so first things first.....

The 1MZ-FE runs a factory 82°C thermostat (which in my opinion is perfect) considering comparable vehicles (Holden 3.8L's run significantly warmer, same with Falcon's 91°C & 92°C thermostats respectively. But fans don't really kick on till 104°C, now i'm well aware the more pressure you have, raises the boiling point of coolant and all that. I don't need that.

 

But my question is, so... seeing as the 1MZ-FE is such a simple engine to work on. Factory fan switch (which controls the cooling fans) in my opinion isn't really the ideal temp for Australian climate.

 

82°C thermostat 

Fans don't kick on till

ON @ 95°C 

OFF @ 90°C 

(Theoretical operating temp @ cylinder head before thermostat with stock fan switch is approx 110°C - 120°C)

Mind you the 1MZ's do have up to 20° higher head temps by design, thus likely to sludge without regular oil changes, they shear oil pretty heavily. Now, i can get a replacement fan switch that drops the temp to

 

ON @ 90°C 

OFF @ 85°C

 

(Now calculating temps that drops the theoretical head temps before the thermostat running a lower temp fan switch to around 100°C - 110°C) - which personally i'm alot more comfortable with. 

In my opinion it's all for emissions, i don't really see an issue in doing so, just to bring head temps down, i'm not altering the operating temp, simply keeping it more in line with the actual temp range (82°C - 90°C) - might help in other areas too. Especially on a hot day. 

 

Bit of info or opinions is highly welcomed 

Kind regards 

Tom

Edited by TommyM
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Remember that a lot of Toyota thermostats are installed on the inlet side to the engine/head (ie the "cool" side, or the bottom radiator hose) so they will be rated significantly lower than the boiling temp of the coolant etc unlike thermos installed in the top hose/"hot" side.  Need to be careful when comparing temps between engine manufacturers.

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8 hours ago, Hiro said:

Remember that a lot of Toyota thermostats are installed on the inlet side to the engine/head (ie the "cool" side, or the bottom radiator hose) so they will be rated significantly lower than the boiling temp of the coolant etc unlike thermos installed in the top hose/"hot" side.  Need to be careful when comparing temps between engine manufacturers.

Pretty sure the 1MZ-FE's thermostat on the outlet side, because i know they have an external cast alloy filler neck. But the fan switch is located on the thermostat (near the starter motor) in simple term. I unplug it, they go into a "default" HIGH fan speed in the event that cooling fan switch fails, if it was a hot day (like that warm day we had in vic not long ago, i unplugged it then turned the ignition on, thus instantly the fans kicked on HIGH), ran them for about 1 - 2mins to cool the radiator down, started the engine and temps plummeted, then i shut it off. It wasn't overheating but i know how it operates on the temp gauge normally vs a warm day. 

Figured a lower temp fan switch won't cause any drama anyhow. I got to flush (well, drain & refill) my radiator with pink super long life coolant anyhow seeing as it's due for replacement.

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17 hours ago, campbeam said:

Sounds like a good idea to me.

Lower head temperatures should help prevent or reduce potential of head gasket blowing. 

1MZ's don't really blow head gaskets, but they sure destroy oil 😂😂😂

Hence why i'm trying an alternative to Mobil 1 0w40 with near or similar specs. 

Hence why i feel dropping the fan switch parameters to 85°C - 90° (82°C thermostat which is factory) instead of 90°C - 95°C. It can only be beneficial realistically. Unplug that switch & them fans really ramp up. The ECU/Air con calls for high speed fans commonly with temps outside past 25°C, which is good. So either that switch calls for them OR the ECU. 

Pretty sure i'm not exactly stupid 😂

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4 hours ago, TommyM said:

1MZ's don't really blow head gaskets, but they sure destroy oil 😂😂😂

Hence why i'm trying an alternative to Mobil 1 0w40 with near or similar specs. 

https://www.penriteoil.com.au/assets/pis_pdfs/HPR 5 5W-40 (Full Synthetic).pdf

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8 hours ago, campbeam said:

I already run HPR 5 in the Calais, loves it. I'm actually trying the GF-S (formally GF-5) next service on the Avalon. Biggest thing i look at is their shear protection. Not to mention it calls for a 5w30 "preferred", no real need to go thicker considering it was on 5w30 before i tried 0w40. Many cars can run 5w30 well past 400,000km, engineers simply would state "you don't need to go thicker" they have a broad temp range to work with

 

Not to mention the ENVIRO+ GF-S/GF-5 is a f**king brilliant oil. I've just been trying to find a trusted oil that actually protects, does what i want, keeps the engine clean, etc. I'm not leaking or burning oil so 5w30 is offering very similar specs to the 0w40, which is more closer to a 30 weight than a 40 weight when hot.

Edited by TommyM
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14 hours ago, TommyM said:

Pretty sure the 1MZ-FE's thermostat on the outlet side, because i know they have an external cast alloy filler neck

Nope, bottom hose (so cool side/engine inlet)

spacer.png

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52 minutes ago, Hiro said:

Nope, bottom hose (so cool side/engine inlet)

spacer.png

I've actually seen so many diagrams with two sensors on that side, so i was like "hang on where's my bloody diagram with the single fan switch" lol

But thanks to you, well it's the switch i'm after. So knowing it's the cool side, a lower temp fan switch can only be beneficial then 😁

I dunno why some are vertical & others horizontal 😂

Different applications maybe ?, Lexus might call for a different placement, etc. The Avalon's up until 09/2003 had a lower temp fan switch that came (ON @ 90°C) (OFF @ 85°C) ones built after 09/2003 were fitted with the one below.

Dunno why they went to a hotter one for (ON @ 95°C) (OFF @ 90°C)

Edited by TommyM
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