Brake fluid (dot 3) in the transmission

[nimnar]

I drive a 2001 Corolla and put very few miles on it each year--right now it has about 100,000 miles on the odometer.

The transmission is occasionally a little rough when shifting but I haven't noticed any slipping. An old-school mechanic I use for oil changes thought he saw a small leak in the transmission case and suggested half a cup of dot 3 brake fluid, which I let him add. Now I'm having second thoughts.

Could this make any sense long term? Will this amount of brake fluid damage the 16 year old transmission? Does anyone have any experience with such things?

My goal is to continue putting 5000 miles a year on this car for the indefinite future. Thank you in advance for your comments.

 

[kschachn]

Interesting, first we had someone adding brake fluid to the cooling system and now it is the transmission.

Not all elastomers are resistant to brake fluid, and I would not trust that the ones in my transmissions are. Yes it will likely cause them to swell but it also may cause them to degrade and disintegrate.

If it were me I'd cooler line flush that ATF and find a new mechanic. But maybe that's just me.

 

[CorvairGeek]

An old trick to swell/soften seals. It may swell more than you want. The old timer that told me this as well said to change the fluid before it swells 'too much'. I don't quite know how to quantify that.

 

[bioburner]

I would be changing the fluid out and giving Valvoline Maxlife for tranny a shot. Its supposed to have a additive package for helping restore seals etc and its touted for vehicles over 75k

 

[Kuato]

No. Have the fluid replaced with the correct fluid. Transmissions are designed to run on fresh fluid, not old dirty fluid and certainly not brake fluid.

 

[Leo99]

I would stop worrying. By doing nothing you should get another 50k miles on it.

 

[RF Overlord]

I agree with the others above: get that stuff out of there ASAP. Take it to a shop with a fluid exchange machine and make sure they use the correct fluid for that year Corolla, not some generic universal fluid.

 

[i_hate_autofraud]

Brake fluid is a mineral oil, not nearly the same as ATF.

If you had rough shifts, I'd wonder if the tranny filter was ever replaced, the OEMs design them to plug way sooner then in the past!

Then I'd look at a proper ATF additive instead of DOT 3 fluid. So far I've found Seafoam Trans Tune to work great on GM 4T65E trannies, not sure about a Corolla tranny.

In your case also check the true tranny fluid level after a 10 mile drive, I was surprised to find a 'hot engine' from idling is not the same as a 'hot tranny' from driving, a false fluid level on the dipstick will mislead. If you're anywhere near the low limit, it can contribute to rough shifts.

 

[kschachn]

Originally Posted By: i_hate_autofraud
Brake fluid is a mineral oil, not nearly the same as ATF.


I've never seen a mineral oil based brake fluid. If it were, then it would be compatible with ATF.

 

[Tman220]

Originally Posted By: i_hate_autofraud

Brake fluid is a mineral oil, not nearly the same as ATF.


You're right about brake fluid not being nearly the same as ATF, and that because it is Glycol Ether based, not mineral oil.

If It were me, I'd flush that stuff out, brake fluid has no place in a transmission

 

[ragtoplvr]

This is the old car dealers trick. Put some brake fluid in what ever part is leaking. Drive car a few times. Detail, steam clean and turn it quick.

The kid of one of my friends bought one treated with Dot 3 (as we found out later). The leaks came back with a vengeance. We called it the Exxon Valdez.

Get transmedic or something made for transmissions.

Rod

 

[eljefino]

Get it out of there. This car should have a drain plug, and it would be easy. But do it even if it's hard.

 

[JimPghPA]

Drain it and refill but add some ATP AT-205 Re-Seal that you get from Amazon.

 

[MolaKule]

Originally Posted By: RF Overlord
I agree with the others above: get that stuff out of there ASAP. Take it to a shop with a fluid exchange machine and make sure they use the correct fluid for that year Corolla, not some generic universal fluid.

Make sure you get ALL of it out of there using a complete replacement strategy.

Uneducated mechnics can sometimes do more harm than good.

Never let a mechanic add ANY OTC product to engine oil or transmission fluid.

 

[meborder]

No fluid additive in the world will help with a leaking case.

Get it flushed.
This was a bad plan for a guy who wants to keep his vehicle indefinitely....

 

[Nissan101]

Same
A person also told me that it can help with slipping....not too sure on the topic though

 

[Yah-Tah-Hey]

That "old school mechanic" is probably "Pop" in one of the Seinfeld episodes where Pop is tinkering around on the LeBaron engine. LeBaron went up in flames a few episodes late. Paaaaaaop!!!!! You gotta like it.

 

[nthach]

Glycol will wreck the friction material in a tranny. Get it out ASAP, if you must swell the seals before a proper rebuild use Trans-X or AT-205. Only thing should be in there is ATF, any Dex/Merc fluid will work in those.

 

[MolaKule]

Originally Posted By: Nissan101
Same
A person also told me that it can help with slipping....not too sure on the topic though



Yes, by pouring it on iced-over concrete.