Fan Clutch Fluid?

Driving up mild inclines on the highway yesterday my coolant temp got to 207 degrees. Also noticed TC temp was getting to 210, which is never seen it over 186 before. It was 90 degrees, 65% humidity, inclines af maybe 3-4 degrees but a mile or so long. I don’t think I’ve ever noticed it get above 195 before (always between 184-195). In the LC community, we’d add fan clutch fluid of a thicker kind and it made some big differences. Is that something anybody does on a 2nd gen Tacoma? I have an OR so it came with the pink fan clutch (some of us swapped out our LC stock ones for these pink ones), which is a pretty good and stout fan clutch. 102K miles. All original parts. I’m going to flush the coolant and replace it but wondering about the fan clutch fluid.

 

On the highway, you don't need the fan. You can take it off and throw it in the ditch. If you are experiencing high temps at highway speeds, it's not a fan problem. Try blowing the dust out of the radiator.

 

Op, its a silicone oil and available from Toy dealers.

 

You can always add a pusher fan and a tranny cooler if you don’t have one, or if you do get the bigger one

 

We don’t use that oil. We use RC car shock silicone oil. Usually in the 10,000-15,000 range. Toyota is only 6,000 or 7,000.

 

Thanks for that info.

 

x2 Exactly, something is failing within your cooling system.
It's finally being exposed from the heat.

 

Totally slipped my mind the fan does next to nothing going down the highway. Thanks.
We’re about 4 hours from home so hopefully we make it back before whatever it is totally shits the bed.
I just sat in a drive thru for ~10 minutes. It only got to 195.8 degrees and it’s now 97 ambient temp. I haven’t washed it in quit some time so I’m going to find a self service car wash and gently spray off the radiator and tranny cooler. They’re probably coated in dust and bugs. I’m going to let it cool a bit and look in rad. to make sure it’s full. I know the overflow, when warmed up, is about halfway full.

 

Just went on a 15 mile highway drive. 92 degrees. Spraying off the radiator didn’t help.
Flat highway and it’s stays about 190-194. Slight inclines and it hits 204.
It never hit 204 last summer. Not sure what’s different now. Coolant level is normal, no leaks, etc. What’s weird is it seems the tranny is running hotter as well. Never seen it get above ~175 before but this trip it’s been over 205 multiple times.
Hope we make the 250 mile trek home in the morning!

 

That's a real bummer. I'm in Houston and the heat index is nearly 110, which doesn't really help either.

A few things I would probably do in this scenario:
Check radiator cap seals, ensure no air is in the system and water pump is good and not weeping.

 

I believe the tranny fluid goes through the radiator before the cooler and the life of the coolant is 10 years or 100k. If the radiator isn’t cooling enough well then you know the rest. If you’re not low on coolant or leaking, then I’d start with replacing the thermostat and radiator cap. You can do a water pump while you’re at it but may not need to.

 

I’m in New Braunfels right now. There’s a bit of humidity, making it feel like 103.
No air in the system, don’t see water pump weeping, can’t tell if the cap is good or not. There’s a Toyota dealership about 10 miles into my trip home. I might swing in there just in case.

 

I tend to go overboard so if I replace the t-stat, then I’ll also replace the water pump, all hoses and flush the system a couple times. I planned on doing it this fall but looks like I’ll be doing all that a lot sooner.

 

I wrote a lengthier response earlier that included replacing those key components if you were to tear into the cooling system. I do agree with you on overhauling the system while you're at it because it is cheap insurance. I also believe the thermostat would be very likely causing your issues as the spring may have deteriorated and compromised your vehicle's cooling capability.

That being said, I would start with the cheapest fix first and confirm your radiator cap's integrity.

 

If you replace the thermostat get a OEM unit from Toyota. It’s worth the added cost.

 

Yes, I do this on all my Toyotas. I buy a OEM one, crack it open drain, adjust the on temp, and fill with RC oil. Then throw my stock one in my toolbox as a backup.

Has worked well on Tacos, T100s, Tundras, 4runners, and Fjs.

 

Just drove a bit. When cold, the overflow was at the low line. Once warmed up, it was halfway between the low and full mark. This leads me to believe the rad. cap is doing its job, correct?

 

Elevated trans temp tells the tale. On GM vehicles I've seen them boil the radiator from the bottom - divorcing the trans cooler from the rad worked wonders on engine cooling system.

 

Sounds like it is functioning correctly. As @GREENBIRD56 stated, trans temp is a definite indicator. The transmission fluid has a line that runs into the radiator on automatic vehicles. When the vehicle portrays warmer than usual temperatures, this in turn will reflect in the transmission temperature. I'm going to recommend the thermostat to be swapped out.

 

Made the trip home. Engine temp stayed about 204 degrees going 75+mph. When I’d drop down to ~60mph, temp would drop to 190-194. ~45 and slower it’d drop to 184-186. Higher RPM’s didn’t change temp but load definitely did.