Three Year Brake Fluid Changeout

[Glenn C]

I had to Google the "for safety reasons" comment. I've been working on cars for the better part of 4 decades and have been flushing brake systems for nearly as long. I've never read anywhere in any technical documentation or the numerous repair manuals I've collected over the years that stated brake fluid is purposefully formulated to absorb water (and especially for "safety reasons"). My understanding has always been, brake fluid chemicals absorb water over time and require changing because the absorbed water (a) can lead to internal corrosion of the brake system, and (b) can create reduced braking effectiveness at high fluid temperatures if the air trapped in the fluid boils (turns to gas vapor) and causes a "spongey pedal".

Too my astonishment a Google search did bring up the idea DOT 3, DOT 4, and DOT 5.1 are formulated to suspend water in the fluid to prevent "pooling" in the system and reduce the chance of corrosion forming in the brake components. I found the "pooling" phenomenon is discussed in relationship to DOT5 fluid, which is silicone based and doesn't absorb water, which makes sense. But DOT 3/4/5.1 being purposefully formulated to absorb water "for safety reasons" (i.e. corrosion prevention via "pooling") I'm not buying that argument. The internet is full of misinformation.

DOT 3, 4 & (I think) 5.1 are made with glycol ethers which are hydroscopic. They were used because of their boiling point, the hydroscopoic nature is an undesirable property but glycol ethers are cheap compared to compounds with similar boiling points. The only water that sould get into the system either comes from contamination or from the huidity in the air that is sucked in as pads wear and the fluid level drops. I suspect the 3 year change recommenndation was developed empirically because the glycol ethers used were by-products (I worked for years at a chemical company that produced them) and have impuruties that oxidized to acids that caused corrision, much like old coolant formulations based on ethylene glycol did in the coolong systems. DOT 5 Silicone fluids don't have this issue, but they require more expensive elastomers in the seals.

Sponsored

 

[dalola]

Timbucktoo is near Perfection, but no one knows how to get to either place...

I'd bet it would take decades for enough water to pool in a brake system to cause an icing problem, but as always, one should follow the manufacturer recommendations for brake fluid type. Since DOT5 is not compatible with conventional brake fluid and nearly every production car (I'd bet every one) sold to the public for street use uses either DOT3 or DOT4 brake fluid, adding, or even flushing a DOT3/4 system, and using DOT5 would damage the system regardless of freezing temperatures.

My debate is with the internet saying DOT3/4 brake fluid is formulated (for safety purposes) to absorb water - the safety reasons being corrosion prevention and freezing of pooled water in the system. I'll stay with what I've learned over the past 35+ years that DOT3/4 brake fluid is flushed periodically to prevent corrosion in the system because the fluid has accumulated too much water content. In other words being that DOT3/4 attracts water is a bad chemical trait and increases the risk of internal corrosion.

DOT5 will not "damage" a brake system, it's a superior fluid as far as actual braking performance, but not being hygroscopic makes it a poor (unsafe!) choice for passenger vehicles. So, you think it's just bad luck that DOT3/4 brake fluid absorbs water? You really think chemical engineers are that stupid? WOW. ?

 

[RockinVs]

Was curious about this as well. Not that I need it any time soon on my MME.

I just had the brake fluid flushed in my mazda 3 for the first time. 12 years old, 120000 miles.

 

[steve.panse]

I’ve always bled my own brakes to change fluid every 2-3 years, with the two person pump-the-pedal method.. At the cost of a few quarts of fluid it’s cheap insurance against corrosion and component failure, as well as loss of braking under emergency stopping.

I’d rather not take it to the dealer for this, would love to hear from anyone who has tried it…successfully or not.

 

[ChasingCoral]

I was wondering what in the world y'all were talking about. I looked again at the maintenance schedule on the app and there is nothing about the brake fluid change.

So I searched the MY2021 Manual and found this on page 370:

You find the same thing in the 2022-23 manuals.

However, the 2024 manual doesn't have these two tables.

The 36 month brake fluid doesn't appear in the maintenance items in the app. However, the "Other Maintenance Items" do appear at 20,000, 150,000, and 200,000 miles. ?‍

I guess I'm overdue for fresh brake fluid.

 

[GreaseMonkey]

I was wondering what in the world y'all were talking about. I looked again at the maintenance schedule on the app and there is nothing about the brake fluid change.

So I searched the MY2021 Manual and found this on page 370:

You find the same thing in the 2022-23 manuals.

However, the 2024 manual doesn't have these two tables.

The 36 month brake fluid doesn't appear in the maintenance items in the app. However, the "Other Maintenance Items" do appear at 20,000, 150,000, and 200,000 miles. ?‍

I guess I'm overdue for fresh brake fluid.

I noticed the same thing. It’s unusual that they wouldn’t list all items under maintenance schedule regardless if they are based on distance or time. My Mach-E has 13k miles after 2.5 years and it’s very confusing to figure out what’s due when.

 

[eponey]

This car has no maintenance schedule, it's all literally made up. Changing a cabin air filter based only mileage is the dumbest thing that anybody has ever written down. Just wait till you try to go to a dealer and they don't even know what the maintenance schedule or tasks are...lol.



2024 manual says go to ford.com to see the maintenance schedule and ford.com says look at the manual, singularity complete, cheers ford on your incompetence hahahahahaha

 

[pottslaw]

I asked my dealer about the 30K brake fluid replacement requirement. They tested the brake fluid and said it did not yet need to be changed. I live in Arizona so it is hot and dry most of the year. I will ask them to test it again the next time I take it in.

 

[Ned]

Correct advice is always follow maker’s specifications.

It’s there for a reason.

Changing brake fluid is a preventive measure worth taking - a good insurance policy.

Not only is there a risk of vapour-locking and so complete brake failure, there is a risk of the hidden effects of moisture and other wear debris within the hydraulic system corroding, deteriorating and wearing parts from within the consequence of which we’d all moan about when they let us down and we would not know that the brake fluid was the reason.

I have been driving for 70 years and over a million miles and have never changed brake fluid (or cooling system fluid on older cars). I normally trade in before 100,000 miles.

 

[zvez]

I looked at the newer manual for the 24s and as others have stated, they've apparently removed the replacement intervals for everything, now it seems it's mostly visual inspections and replace as needed.

 

[Teslaeata]

I have been driving for 70 years and over a million miles and have never changed brake fluid (or cooling system fluid on older cars). I normally trade in before 100,000 miles.

So what ??‍

 

[eponey]

I looked at the newer manual for the 24s and as others have stated, they've apparently removed the replacement intervals for everything, now it seems it's mostly visual inspections and replace as needed.

Nah it's more like the dealers complained so now they can do whatever they want and you can no longer be an informed consumer.

 

[Trick.Mach-E]

Timbucktoo is near Perfection, but no one knows how to get to either place...

Perfection (AKA Rejection Valley) is pretty easy to find.

As always, be on the lookout for American Graboid's that are known to be in the area...

Sponsored