Cooling issues? Not anymore

2nd gen here, fully stock cooling system which is identical to 3rd gen, done that drive MANY a time up the backside of the grapevine loaded down, most recent was in ~100*f ambient, doing 65+ loaded with ~2.5klbs total between gear and a stand up jetski in the bed + 2 jetskis on a trailer just letting her sing in 3rd n 4th, temps never got above 205 with the AC blasting. Never understood why someone would ditch the stock mechanical fan all together, when heated up there is hardly any parasitic drag if its not needed, comes in when needed, no programming to worry about etc.

I COULD see adding a supplemental electric pusher fan to aid in low speed stuff/AC performance if you were having those issues in those conditions, but there is a reason why almost all full size trucks run a mechanical clutch fan.

 

You shouldn't need a fan at 65, if you do you have other issues. But they eat up more HP than you think. Here's back to back dynos from MotorTrends Engine Masters episode on exactly this (on a SBC). You can see how much they hurt both unlocked and locked.

This is an unlocked clutched fan.





Fixed fan which should be about the same as a clutched fan when fully locked.

 

Loaded, high ambients, almost WOT for lengths of times, yeah you will need a fan at 65 or even 45 (especially if you are in the wind column of a busy highway), just ask the poster above. Id gladly take a slight hit in power/torque to have the knowledge that I can climb a BUSY ass highway grade without a worry in my mind.

 

Did the cooling fan change on the 2021 models?

 

The faster you go the less you need the fan. But if you need the fan at that speed it means the clutch is locked and its not a slight power hit. It's a big one. A third gen will be at 4500+ rpm to pull that hill with that load and be using nearly 30 hp to turn the mechanical fan in your example. While the electric fan at full blast will be drawing less than 3 hp and properly setup have no issue cooling the truck down.

There's no way around it; an electric fan is much more efficient in every scenario. We still have mechanical fans for the same reason we have drum brakes. They're cheap, simple and get the job done. But that doesn't mean there isn't a better option out there.

 

No doubt that an electric fan is more efficient.

But, reliability wise when it matters the most, debatable. Quite a few people have done aftermarket electric fan setups and have gone back from that standpoint. To each their own, just pointing out that the person I initially quoted would of not had a single issue driving up that grade with a stock cooling system.

 

I agree, though I do not like the idea of using the Lengenfelter 100% trigger wire. Full load amp draw in stop and go traffic would quickly be a problem.

In looking at the sensor chart for the electric fan, the resistance of the sensor goes down as the temperature rises. This is good, so we can install a NO relay and resistor in parallel with the sensor; energize the relay from the compressor; to put the resistor in parallel with the sensor, and affect the sensor reading enough to kick up the fan speed a notch. This should work really well, as it would fail safe; meaning if the relay fails, we are never breaking the sensor circuit, so the sensor will still work properly (as opposed to needing the relay to be series).

I am going to try a 4K ohm resistor, as this seems it would boost the temperature reading 20 to 25 degrees F in the neighborhood of my operating temperatures (affect of resistor varies on a curve, depending on sensor temperature at the time; I chose this resistor, as my sensor will be immediately after the radiator; cooler sensor temps). May take some monitoring and tweaking, but seems like this should work.

 

I don’t wrangle pixies so I’m not 100% sure what you’re getting into, but it sounds solid. Basically the relay closes when AC clutch is engaged, then the load side of the relay “introduces” the resistor to the fan controller to report a “higher” temp? Only thing I’m curious about is the ability for the fan to ramp up fast enough, even with the 100% bypass switch, the ramp up is pretty slow, so the AC clutch might be off by the time the fan reacts.

I’m not that big of a fan of having the temp sensor before the rad. But it does lend itself well to cooler AC temps. Be curious to see how this experiment plays out tho!

 

Alright I did this to my 92 3.0 and yes the results were amazing way more power

 

Do 3rd gens have a water to oil oil cooler on the tow package trucks? I know the 2nd gens did - so basically most all 2nd gens. Ive never seen a cooling circuit diagram, but would imagine the water circulating the cooler would be pre-tstat? In which case Id imagine the ambient temp doesnt have much influence over the oil temps and probably warms up quick, once the engine is warm.

 

Yes and yes.

 

So I did a few things to help out free air cooling (for a/c and engine), and to run the fan a bit more than necessary and help out A/C with the fan. I cut and installed the flapper vents from the GM fan into the corners of the Toyota fan shroud, I added baffles to seal up everything from the grill to the radiator, so ALL air that crosses the grill must pass thru the radiator.

I also did research, and found that the difference between the inlet water temp and the outlet is 20 deg F. so for normal running temperatures, and a 195f T-sat, we technically are good with 175f, entering water temperature, but I set my electric fan start temp. at 140f. Figure this is pretty easily attained by free air, at normal loads and speeds over 45, even on a hot day, so should minimize how often the fan runs, a considerable degree. Yet this seems it may be plenty low enough, that in slower speeds, it may well run the fan often enough for acceptable AC cooling. Ttime will tell, and I can always add the relay and resistor, if it proves necessary. For now, simpler is better. When we get a real hot day, I will report back.

 

@Pinchaser great mods! Did you measure these temps? The Taco has the weird heated t-stat that helps the thermostat open quickly to reduce temps under heavier loads...

From Toyota...
When the ECM determines that the engine is under a high load based on the engine operation and load conditions according to signals from various sensors, current is supplied to the heater element in the thermostat sub-assembly in order to open the valve of the thermostat. Therefore, it ensures the fuel economy by raising the oil temperature and reducing the friction when the vehicle is on light duty. It also achieves lower water temperature that assists opening a vent by heating the wax inside the thermostat while the vehicle is on heavy duty.

 

For me, the controller settings are basically moot. Like air is gonna flow through the rad basically no matter what, (as long as your settings aren’t supremely dumb and temp sensor is at the outlet). My issue the the warm up. Like some times the truck will take quite a bit to warm for the controller to start adding pwm to get the fan going. It can be brutal. Even if the temp is reasonably warm. I’m grateful for your contributions here. This is the exact fine tuning road that I love going down.

 

Just curious but when tacoma and 4runners start up, the fan blows loud like a big storm and I don't hear it from any other truck or BoF suv. Anyone know why the tacomas and 4runners are so loud in start up?

 

• Jowett, I did not measure them, and not even sure which temps you are asking about. The research temperatures are generic from the internet. Very interesting Toyota statement, and I didn't know it had a heating element at the T-stat. I may want to find that and tweak my control scheme. I was disappointed to learn how the Lengenfelter controller works, as what I think would work better is a controller that varies fan speed to maintain a steady temperature at the sensor. Then we can use it at the inlet to the engine, and maintain a target (cool enough) temperature. But it ramps up according to the delta between start and 100% settings, and too narrow a delta will probably make it hunt. So with the electric T-stat, I could use that heater signal to energize a relay, that connects a resistor in parralel with the fan control sensor, and trick the fan to ramp up speed (same idea as for the A/C ramp up mentioned elsewhere.)
  
• So what is the easiest way to actually see the temperatures i am running at? do I need to add sensors and a gauge? Right now I am just seeing that the factory Temp. Gauge stays pointed up the center.

Skydvrr, why do you care how long it takes for the fan to start spinning? you want the engine to com up to temp quickly, and running the fan sooner than necessary is only defeating that (by lowering the coolant T entering the engine, lower than needed, and by blowing more air under the hood; contributing to cooling the block. Is this an A/C issue for you?

If the fan does this for more than a minute or two, it typically indicates a bad fan coupler. If only stays loud for a minute or so on start-up; then I speculate that the viscus coupler of the mechanical fan, may operate on a U-shaped curve for temperature. Though it is designed to couple tighter with T-Rise, it seems that at some low temperature, that the coupler becomes stiff, like the oil thickens in cold enough temperatures; and that oil needs to warm up before it can properly De-couple. I think that the friction within the spinning coupler, is enough to warm itself, so it decouples fairly soon after start-up, independentof the engine temp; and the fan quiets. Again this is speculation, to make sense of why it might act this way. Maybe someone else has learned something more specific on this.

 

The 175 and 195 t stat temps you listed... I was hoping you had measured them so we have real data to pull from. If we can pinpoint the thresholds for activating HD mode, we may actually be able too see coolant and oil temperature drop, depending on how much load there is.

 

Was really hot Friday, and i was on a road trip. Learned that with by bottom hose sensor for the fan; from a cold start, the AC blows warm in stop and go, parking lot traffic, for an uncomfortable amount of time (until the engine temp is full up, and exchanges the full volume of the radiator too). This is Without the resistor/relay mentioned in a prior post. I also learned that at only 20 mph, the AC was wonderful Cold, Fan still OFF; so it does not seem to need much air for the AC. I am going to add the resistor/relay for sure, BUT also brainstorming, as what I really want is for: if the AC is on, want the fan to run at its slowest speed until or unless, the normal fan sensor is calling for fan, then that should dictate. The Lengenfelter does not provide this option, it only has an option to run by sensor or be triggered for 100%.

Going to add the relay/resistor and see how it goes, but already know this will have an impact to fuel economy, just hope it is small.

With regard to the electric fan and fuel economy, I did some calculations, and was surprised at the outcome: This truck has a mechanical fan delete, and the electric fan is off at highway speeds (and runs variable speed only as needed at other speeds). The sensor is at the bottom hose, very near the radiator, and fan starts at 140f, so as long as free-air cooling is effective in the radiator and cools the fluid to below 140, the fan remains off. This fan at full speed is 70 amps, that totals very near 1000 watts, so with engine efficiency at about 33%, this means running this fan at 100% for 11 hours burns one gallon of gas, or 0.09 gallons/hour to run the fan. This translates to that: 19.5 MPG (without fan) would be reduced to 17.7 (With fan running 100%); a difference of 1.8 MPG just to run this fan at 100%. This also translates for a general sense, that if the Toyota mechanical fan happens to move an equivalent amount of air as this electric fan (seems it is likely to be considerably less, but just for the understanding), then simply deleting the mechanical fan on a stock truck would increase fuel economy by this same 1.8 MPG for daily driving. I say for daily driving, because if your current fuel economy is substantially less than 19 MPG, then the 1.8 MPG for the fan will also be less; as the fuel saved by turning off the fan, will carry the truck a shorter distance. Moral of this story, Save $10.00/ fill-up, by converting to an electric fan, and controlling it to sense the bottom hose of the radiator, and only run when needed. Return on a $1000 investment is 101 tanks of fuel, or 36,000 miles. (@ $5.50/gallon and 19mpg avg). 3 year return on investment is pretty good. Not to mention the free-ed up horsepower from the mechanical fan delete!

 

What is the reason?

 

That’s pretty nifty math! I agree with everything you mentioned. Terrible warm humid air from the vents with no air over the condenser, but it doesn’t take much mph to get it working nice.

I used a fluke amp clamp on mine and only saw around 50. Idk if that’s an inneffective / dumb way to measure tho. I’m not too keen on the pixie wranglin yet. Haha