Thermostat & Temperature question

[toyotarave]

Hi

If my temp gauge needle during normal driving indicates that it is just slightly above Cold - that means my radiator fan is working overtime right - because the thermostat is open all the time?

If yes, would this increase my fuel consumption - just asking

[mspringer]

Originally Posted by toyotarave

If my temp gauge needle during normal driving indicates that it is just slightly above Cold - that means my radiator fan is working overtime right - because the thermostat is open all the time?

Probably not. My guess would be that the thermostat is stuck "open" and is constantly circulating. Your radiator fan may actually be working less often, because the motor is staying below normal operating temp. (Or, it is working exactly as before - if you drive with the AC on, the fan should be on, regardless of engine temp.)

Originally Posted by toyotarave

If yes, would this increase my fuel consumption - just asking

Maybe, but my guess would be not significantly, and it wouldn't be due to the radiator fan - it would be due to the computer compensating for the lower temps with more fuel and possibly advanced timing. Depending on the ability of the Camry computer to adapt, the car may move to a richer fuel table (and more timing) to compensate for the lower engine temperature.

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Recommend: Change the thermostat and see if things return to normal - on my 4cyl, the t-stat looks to be super easy to change, and the part is less than $10 - go to Autozone or any parts store - its not necessary to get a Toyota part.

WHY: If the t-stat is stuck open, the car is NOT NECESSARILY running cooler. The water may be cooler due to the continuous circulation, but the continuous circulation is also causing less heat to transfer from the engine block, so the engine itself may actually be hotter, and you cannot tell. This is why it is not recommended to remove the thermostat.
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Parts Note & Personal Opinion: The factory thermostat is 195 degrees. Depending on where you live, you may want to try a cooler t-stat (180 degree, which really isn't a lot lower), although the factory would not recommend it (largely for emissions purposes - hotter engines burn more completely, but make less power). A cooler running engine IMO will wear less (less heat fatigue - although this is debatable with today's high quality metals), and may produce more power, although at the low power levels that the Camry produces, this is also debatable.

I have a ScangaugeII, and the surprising thing to me is that (with the temp gauge in the middle, where it always is) my 4 cyl is running at 205 degrees (water temp), which I personally think is too warm, especially since I live in the Houston area, and it hasn't even started to get hot outside, yet.
I will soon be switching to a 180 degree thermostat, just to see if I can get the water temp down. I also think I will add an auxiliary transmission cooler, since the factory cooler is a JOKE - one row on the bottom of the radiator which cannot be cooling the transmission much, and that hot transmission fluid, in addition to wearing the transmission, is heating the water in the radiator.)

[toyotarave]

thanks you've been a great help - with petrolprices as they are now - i want to ensure i get the max of any inefficiencies the engine may have been with up to now

I think where i am in the tropics - a 180 degree stat will be best since it take pretty fast for the engine to warm up

[jatan1986]

Same prob here with my mom's Camry - sometimes it stays at 1/4 or 1/3 above the C and rarely at 1/2 where it should be (averaging 20mpg city/hwy mix with new plugs, O2 sensor, PCV, air filter, and 35psi tire pressure)

Going to change out the t-stat, plug wires, clean TB & IACV, and Seafoam it

[hooRAH]

Originally Posted by mspringer

WHY: If the t-stat is stuck open, the car is NOT NECESSARILY running cooler. The water may be cooler due to the continuous circulation, but the continuous circulation is also causing less heat to transfer from the engine block, so the engine itself may actually be hotter, and you cannot tell. This is why it is not recommended to remove the thermostat.

Most of what you said makes sense except for this. While not necessarily "simple", a simple fluid mechanics or heat transfer textbook shows that heat transfer will increase with fluid velocity. I could go into details, but the point is that the faster the coolant flows, the cooler the block will be.

[Eye8Pussies]

as the others said- check your thermostat- it's an easy fix and cheap as well

[mspringer]

Originally Posted by hooRAH

Most of what you said makes sense except for this. While not necessarily "simple", a simple fluid mechanics or heat transfer textbook shows that heat transfer will increase with fluid velocity. I could go into details, but the point is that the faster the coolant flows, the cooler the block will be.

I'm not a fliud dynamics expert, by any means. I am merely reiterating what I have been told time and time again by mechanics I trust and also other websites. My guess is that there are more variables in an automotive application than a "simple fluid mechanics" model will encompass, otherwise, if what you state is true, cars wouldn't have thermostats at all, as it would be a bottleneck in the system.

Also, my experience with streat racing is that if you remove a thermostat, the gauge will read cold, but the car is much more likely to blow a head-gasket because the heat is not getting pulled out of the head properly.

[hooRAH]

Originally Posted by mspringer

I'm not a fliud dynamics expert, by any means. I am merely reiterating what I have been told time and time again by mechanics I trust and also other websites. My guess is that there are more variables in an automotive application than a "simple fluid mechanics" model will encompass, otherwise, if what you state is true, cars wouldn't have thermostats at all, as it would be a bottleneck in the system.

No biggie, I'm just trying to help out, and appreciate the information you put forward.

The cooling that occurs in the head from the coolant flow is actually very simple, its just simple convection flow over a surface. The complications of the problem are in the details of the geometry of the fluid flow. In any event, yes, what I say is true, the faster the coolant flows, the lower the temperature of the block. Now, the reason why cars have thermostats is to keep the temperature of combustion higher by keeping the block temperature higher (by higher, I mean around 180F.) You want it to be higher than "maximum cooling", but not too high that the oil varnishes and gums up the head. The higher the temperature of combustion, the more efficient the burning of the fuel is.

Originally Posted by mspringer

Also, my experience with streat racing is that if you remove a thermostat, the gauge will read cold, but the car is much more likely to blow a head-gasket because the heat is not getting pulled out of the head properly.

First of all, if you remove the t-stat, yes, the gauge will read cold because the coolant temperature IS low, and the head IS cold. I wouldn't think that this would make the car more likely to blow a head gasket, rather less likely. I will look into it and see if I can dig up any more research on it.

If it turns out that a low temperature head DOES correlate to a higher risk of blowing a head gasket, I would think it would be due to one of two things:

1 - the fact that you're racing in the first place. I'm not against racing in any way (see my sig), but if you're removing the t-stat to lower engine temps (probably because you have a turbocharger) and racing on a regular basis, you're at a much bigger risk for headgasket damage to begin with, or

2 - The thermal shock between a suddenly increased (launching the car) combustion chamber temperature and the low temperature coolant can cause enough deflection to warp the head, which would cause the headgasket to fail.

No offense to your experience at all (like I said, I appreciate you putting the information forward to help this guy), but I am a mechanical engineer with a lot of experience in heat transfer and fluids.