Clutch fluid question

I realize that there are usually a number of posts asking about the stiff clutch pedal in cold temps on this truck, and I kind of get the reason why: The fluid viscosity goes up as the temps get closer to 0F. I've never had this happen on any of the other three manual vehicles I've owned, but ok, sure. I'll just chalk it up to yet another design flaw. Right up there with a AC drain line designed to rust the frame and tag lights designed to blind the backup camera.

I have an idea that I'd like to try but I figured I'd throw it out to the hive mind before I do as an Idiot Check. As I understand it, the Clutch and Brakes use the same fluid and same reservoir and the OEM fluid is DOT3. DOT3 has a maximum viscosity at -40 of 1500cst. I do NOT want to switch out to DOT4 because the maximum viscosity at that temperature is actually higher than DOT3, at 1800cst.

I'm thinking about swapping out to DOT5.1 (not to be confused with DOT5, I know not to use DOT5), which is also a Glycol based fluid (like DOT3/4) but it has a much lower viscosity of only 900cst.

My question to the hive-mind: Will it be safe to replace the stock DOT3 fluid with DOT5.1 for year-round service, or is there some part of the system that will only work properly with DOT3 and DOT4?

 

Don't do it. I tried that on my bike and it shrunk the seals a bit. I thought the master was toast and swapped it. Over time, it also started to weep. Finally remembered that I had DOT 5.1 in there and swapped back to DOT 4. That fixed the weeps pretty quickly. But, I was using Racing DOT 4. That stuff formed solids by missing a bleed . . . on a non-rebuildable master. So, now I'm running regular DOT 3 and bleeding yearly fo sho.


Just a note for the clan, I did not confuse DOT 5 and 5.1.

 

Hmm, I'm not sure how the different fluid could shrink the seals since they are the same basic fluid, but I could see the lower viscosity fluid sneaking past the seals since seals are often designed with the viscosity of the fluid in mind (more viscous fluids don't need as tight of a tolerance). Hmmm.

 

Just use what you are supposed to use

 

Could be. Either way, you don't want the fluid weeping inside or underneath. I didn't have any significant issues with air getting in, but you wouldn't want to risk that either.


BTW, the reservoir is combined on the SR and Sport but separate on the OR and Pro.

 

I prefer to address design flaws rather than just live with them, if I can. Every time I jump in the truck when it's in the teens my first thought after I start the truck and release the clutch is, "How the fuck did Toyota screw that up?" 1997 Nissan 200SX, 1982 Datsun 280ZX, 2013 Mazda3, hell even my wife's 2015 Impreza doesn't have this behavior. Yet, all over this forum the consensus for Tacoma's new and old is "yeah, that's normal."

 

You delete your accumulator already or no?

 

I don't think there's any concern with air getting in, but if enough is weeping out to cause drops to form that could be bad news for the paint on the rear of the truck.

Also, why on earth would they be separated for the OR and Pro? Every day I'm learning something about these trucks that makes me go

 

I have not. Is that the actual reason this is such an issue with these trucks? I don't think any of my previous vehicles had one.

 

Pro/OR trucks use a different/better brake system than the rest of the lineup.

 

If it is getting out, there is alway a possibility of air getting in.

Never had a paint issue with brake fluid. But, you are correct that it can mar paint.

The OR and Pro have a different, electrically boosted brake system. Not sure why that needs a separate res as it uses the same DOT 3, I believe.

 

The ADM helps only a bit with the cold pedal. I actually recently experienced it for the first time and I've had the ADM for years.

 

It's not just this forum. Engineers design specific parts with specific tolerances requiring specific viscosities.

As others stated, the PRO/OR setup is different. It's not a design flaw... it's just cold AF.

 

Ah, ok. Fair enough. Now I'm extra glad I got the OR.

 

Damn... was hoping for a silver bullet.

 

just lookin at Ur mental excercise the mental permutations are abundant

no way U can cover them all

not actually knowing the environs U operate in no one can advise U

DOT brake fluids vary widely so its a crap shoot to recommend or guess to make a choice

the one basic rule is NOT TO MIX Them a slurry mix will usually occur

any hope.....gain.....upgrade will be lost if that occurs

 

Sorry, but folks say that it still happens. It is definitely worth doing though and takes minimal effort if you have something to pinch off the res line and a flare fitting wrench. 10mm if sticking with the dremel method.

 

lol, I've been through colder, a lot colder, in other vehicles and I've never had this happen. I'm not sure what Nissan, Subaru, and Mazda figured out but I wish Toyota would get wise to it.

 

I mean, if I'm going to replace the fluid, I'm going to do a full flush not just turkey-baster it out of the reservoir, fill it back up with new stuff and hope for the best. That would be silly.

 

I hear ya man. It's always something across the board. Does it at least get better when it warms up?