ATF added to brake fluid. What, specifically, are the implications for ABS?

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Not my finest hour, but yes, I added ATF to brake fluid. Less than an ounce, about a week ago. I know to restore the vehicle to safe operating condition, all things rubber must be replaced in the brake system. Ergo, the entire brake system must be replaced. Not negotiable. That's already been bought and paid for and the vehicle won't be operated until that's done. That is calipers all around, hoses, a flush, a master cylinder.

What I cannot find consensus about, is the ABS system. Some are saying it gets replaced with all else. Others say various things:


- probably fine. If the flush happens and it still works, you're home free.

- maybe the ABS will be killed due to my stupidity now or at a later time, but that just means it'll be like driving a car without ABS.

- the ABS is a time bomb; it may function perfectly now but can contaminate newly installed components in the future.

-if you do attempt to reuse the ABS, the flush must occur with denatured alcohol, not brake fluid. Then again, I've heard denatured alcohol can be harmful to the very rubber components we're trying to save here.

My mechanic is of the opinion to pressure flush, and then hope for the best. But I don't think he thought about it until I asked.

I trust the opinions of BITOG more then anyone else in real life or online. But I really didn't want to admit what I did to you all! Hoping for clarity. Thanks all.
 
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I know to restore the vehicle to safe operating condition, all things rubber must be replaced in the brake system. Ergo, the entire brake system must be replaced. Not negotiable. That's already been bought and paid for and the vehicle won't be operated until that's done.
Says who? The shop that is going to profit on all the parts and labor? 1 oz. in the reservoir? Suck it out and replace with brake fluid. Maybe do a flush for good measure. If you have problems down the road, take care of them then, but unlikely you will. What car is this anyway?
 

3Aone

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Ok. The replace it all information i found prior to my mechanic. His initial intention was flush and fill. I found it in more than one place, including here, to replace all rubber. I drive a lot of miles, sometimes with my two year old in back. I gotta sleep at night. Plus, two weeks of operation, you know? I only realized it when the brakes got spongy yesterday. Could very well be air introduced when I added that atf. The reservoir was pretty full.

This was a 17 forte. Atf was maxlife- I've even heard I am in the clear because it's full synthetic! (I wish.)
 
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I have some questions about adding brake fluid at all.

In times past, the level only went down as the pads were used up. When the level was low you probably needed new pads or you had a leak.

I change out the brake fluid about every 3 years and between changes I don't find the level changes much.

I check the level periodically but haven't had to add brake fluid for about 20 years.
 
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I gotta sleep at night. Plus, two weeks of operation, you know? I only realized it when the brakes got spongy yesterday. Could very well be air introduced when I added that atf. The reservoir was pretty full.

This was a 17 forte. Atf was maxlife- I've even heard I am in the clear because it's full synthetic! (I wish.)
What does the rubber seal in the cap look like?
 
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Ditto on the above. The only time I EVER even take the top off the master cylinder is if I'm bleeding the system. Under normal conditions, you should never ADD brake fluid.

During a pad swap, when you compress the caliper pistons, it will push the fluid back into the master cylinder and will likely overflow it.
 
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Trav wants you to see if the rubber seal is going soft, kinda mushy, since you say the brakes are spongy, i would go to DOBBS, They replaced a rotted brake hose and flushed and filled the system on my 2005 Century, for $200, so the flush should be about $80.
 
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I think the thing that worries me is that you drove two weeks with the system contaminated and now experiencing a spongy pedal. If the transmission fluid was introduced and you quickly knew you screwed up and siphoned it out? I wouldn’t be concerned, but it’s a different story with two weeks.

As for the ABS module...I would unfortunately think it is damaged as well, but you could take a chance with that for a bit to see if it’s malfunctioning (And then replace it if it is). Sucky situation all around.
 

3Aone

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I think the thing that worries me is that you drove two weeks with the system contaminated and now experiencing a spongy pedal. If the transmission fluid was introduced and you quickly knew you screwed up and siphoned it out? I wouldn’t be concerned, but it’s a different story with two weeks.

As for the ABS module...I would unfortunately think it is damaged as well, but you could take a chance with that for a bit to see if it’s malfunctioning (And then replace it if it is). Sucky situation all around.
Right. I am hoping maybe there were some bubbles in that atf,i think there were, and i just put air in. The sponginess was barely perceptible, someone who didn't drive the car every day wouldn't have noticed. The pedal wasn't going to the floor; it just wasn't responsive to the lightest tap like normal.

Ok, take a chance for a bit.... am I taking a chance losing ABS, or taking a chance losing brakes?
 
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It really comes down to chemical compatibility of the various seals used in the braking system and if they are compatible with both ATF and brake fluid. EPDM is most commonly used in brake systems and in theory it has BAD chemical compatibility with ATF or any hydrocarbon.

That being said, as a bit of anecdotal evidence I have accidentally mixed mineral oil and brake fluid on my bike's brakes (Shimano and Avid) but flushed it out after a day and have yet to have any issues. Shimano uses hydraulic fluid and Avid brake systems use DOT brake fluid.
 
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Right. I am hoping maybe there were some bubbles in that atf,i think there were, and i just put air in. The sponginess was barely perceptible, someone who didn't drive the car every day wouldn't have noticed. The pedal wasn't going to the floor; it just wasn't responsive to the lightest tap like normal.

Ok, take a chance for a bit.... am I taking a chance losing ABS, or taking a chance losing brakes?
Flush it through now not tomorrow. Get some 90x% IP alcohol and flush that through followed by brake fluid, a couple of quarts will do to get any oil out of the lines and parts, you will need to activate the ABS pump with a scan tool. Now at least you will have stopped the damage.
I would get a seal kit pop the master cylinder and dissemble it check the seals against the new ones, if they look okay you possibly dodged a bullet as those would be the seals effected first, if not you have a resealed part ready to go back in.

If the seals are soggy you need to reseal (not replace) the calipers and replace the hoses which is not a big deal and replace or reseal the ABS pump, you can find a good used one for that.
You can use IPA, denatured alcohol or acetone to flush the system. All pose no issues with EPDM rubber, ATF on the other hand is deadly to it.
I fear it may be too long a time and the job is going to be a bit longer than a flush out.

 

JHZR2

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These systems don’t mix and flow a ton, so I’d start at the top and go from there. Turkey basted isn’t enough to be definite though - you do need to pressure flush the whole system after cleaning the reservoir and checking the MC.

I agree with the mechanic to hold off on replacing abs parts. The system should be functional without ABS, and no guarantee fluid got there. You do need to flush it with clear fresh fluid and then be able to test functionality.
 
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Right. I am hoping maybe there were some bubbles in that atf,i think there were, and i just put air in. The sponginess was barely perceptible, someone who didn't drive the car every day wouldn't have noticed. The pedal wasn't going to the floor; it just wasn't responsive to the lightest tap like normal.

Ok, take a chance for a bit.... am I taking a chance losing ABS, or taking a chance losing brakes?
Honestly, I couldn’t tell you, but let’s say the issue was only isolated to the ABS module...technical if the abs module is not working you shouldn’t lose your brakes, but just the ABS capabilities.

With having a little kid and obviously not wanting to take chances, I’m not all that comfortable giving advice, BUT if it were ME...I’d probably inspect or replace the master cylinder (where the transmission fluid probably resonated) and “chance” it. I know what failing rubber seals feel like...I know what a distorted rubber cup in a master cylinder feels like...I know to pump the brakes and get that seal (sealing again), to come to a stop and then get the problem fixed, but is that something you’d feel comfortable doing? Doing 70 on the highway heading for the exit ramp and realizing...uh oh, no brake pedal...got to pump that brake pedal and get that pedal back. I feel as if I’m in a different situation than you. Me? I don’t want to say I’m unsafe with cars, but I’m so used to diagnosing brake problems, driving with those problems and fixing them (that I’d probably want to save a few bucks, chance it and probably be ok). But I think you’re in a much different situation.
 
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If u drove for awhile and have a spongey pedal, you REALLY need to change all the stuff with rubber in it...and flush lines with brake clean ......that includes replacing the abs hydraulic unit. There are rubber seals in the valve assys. U can also make an insurance claim if u have comp. insurance. If you don't change it, u are taking a risk. Thats my opinion as a dealer tech. And its not about selling parts as I am sure others will chime in. Not only is it almost impossible to clean the abs module, say if you have a valve stick during an abs event, due to valve hang up. U will either quickly lose pedal , or have a wheel ,lock.
 
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