Brake Fluid question
Cruiser
Joined: Oct 2009
Posts: 216
Likes: 172
From: Edgewater, FL.
Where would brake fluid pick up moisture?
My understanding is that brake fluid is hygroscopic, it will absorb moisture. This causes corrosion. i.e. locked up ABS or pitting in the caliper.
Flushing 90% of the fluid reduces the amount of moisture even if not 100%.
I don't know the pathway in a module well enough to even know if any old fluid is still trapped if it is not cycled.
When I had to replace my $863 module it came full of fluid. I was able to install with no need to bleed. I still had a firm brake. Both front and rear.
That was last year, this year I flushed the full system and still a firm lever.
Thanks for the copy Skratch, I must have missed it in my manual. However there is not procedure listed for flushing, only bleeding. And I read your manual as only needing the DT to remove air.
My understanding is that brake fluid is hygroscopic, it will absorb moisture. This causes corrosion. i.e. locked up ABS or pitting in the caliper.
Flushing 90% of the fluid reduces the amount of moisture even if not 100%.
I don't know the pathway in a module well enough to even know if any old fluid is still trapped if it is not cycled.
When I had to replace my $863 module it came full of fluid. I was able to install with no need to bleed. I still had a firm brake. Both front and rear.
That was last year, this year I flushed the full system and still a firm lever.
Thanks for the copy Skratch, I must have missed it in my manual. However there is not procedure listed for flushing, only bleeding. And I read your manual as only needing the DT to remove air.
Road Captain
Joined: Jun 2013
Posts: 671
Likes: 168
From: Ontario, Canada
Ford had basically the same recall on certain model year Fusions. The only way to get any potentially dirty or contaminated fluid out of the pump and some of the valves is to cycle them. Some valves in the HCU are normally open and some are normally closed, depending on what and when their function is. Any fluid behind or around these valves can not be removed without cycling the pump and the valves to flush it out.
Every HCU is designed differently. Some don't even need you to cycle them when installing a new unit, just bleed and go. Others have an extensive bleeding procedure. I don't know about technicians anywhere else, but I know my crew would never half *** a process like this. It's a combination of pride and liability.
Riding your bike an slamming on your brakes will never be enough to cycle through this adequately. How do you even know if all the valves cycled or if the pump ran long enough or at the right times. I'm a 30 year tech and do all my own work. I hate paying anyone to do things I can do myself. Doesn't matter if it's the car, house, bike, whatever. There are, however things that you're better off paying for or at least buying the right tools.
I don't want my obit to say He died while riding his $30k bike, with thousands in upgrades, trying to save $200
Every HCU is designed differently. Some don't even need you to cycle them when installing a new unit, just bleed and go. Others have an extensive bleeding procedure. I don't know about technicians anywhere else, but I know my crew would never half *** a process like this. It's a combination of pride and liability.
Riding your bike an slamming on your brakes will never be enough to cycle through this adequately. How do you even know if all the valves cycled or if the pump ran long enough or at the right times. I'm a 30 year tech and do all my own work. I hate paying anyone to do things I can do myself. Doesn't matter if it's the car, house, bike, whatever. There are, however things that you're better off paying for or at least buying the right tools.
I don't want my obit to say He died while riding his $30k bike, with thousands in upgrades, trying to save $200
Thread Starter
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Cruiser
Joined: May 2022
Posts: 131
Likes: 64
From: Cleveland
You can do whatever you want...
But I used to just do a regular flush, then take a ride making sure to activate the ABS, and then re-flush. I was content with that procedure.... Then I read of all the people needing to buy a new ABS module during the recall... That's when I decided to make sure it was flushed thoroughly, including the ABS module, and bought the Twin Tec, Twin Scan tool...
But I used to just do a regular flush, then take a ride making sure to activate the ABS, and then re-flush. I was content with that procedure.... Then I read of all the people needing to buy a new ABS module during the recall... That's when I decided to make sure it was flushed thoroughly, including the ABS module, and bought the Twin Tec, Twin Scan tool...
My intent is to get a scan tool. I was just trying to clarify from the earlier post saying bleeding is the same as flushing. I know the process is the same, but the goal is different. Kind of concerns me a bit though that I have not done that on other abs equipped vehicles.
all with no need to bleed. I still had a firm brake. Both front and rear.
That was last year, this year I flushed the full system and still a firm lever.
Thanks for the copy Skratch, I must have missed it in my manual. However there is not procedure listed for flushing, only bleeding. And I read your manual as only needing the DT to remove air.
That was last year, this year I flushed the full system and still a firm lever.
Thanks for the copy Skratch, I must have missed it in my manual. However there is not procedure listed for flushing, only bleeding. And I read your manual as only needing the DT to remove air.
Seasoned HDF Member
Joined: Sep 2017
Posts: 12,186
Likes: 4,908
From: England
Still can't believe that you need this to do a simple brake fluid change.
Seasoned HDF Member
Joined: May 2018
Posts: 5,814
Likes: 7,142
From: Las Vegas
It's really this simple ---
Bleeding is getting air out of the system. Nothing more, nothing less. In many cases this leaves cruddy, high moisture brake fluid in the system.
Flushing is replacing the brake fluid in the system, entirely. Because there is fluid in it, this includes the ABS module.
All service manuals assume the user has mechanical ability and knowlege. If it were written with every instruction imaginable it would be as thick as that book on how to understand women.
Bleeding is getting air out of the system. Nothing more, nothing less. In many cases this leaves cruddy, high moisture brake fluid in the system.
Flushing is replacing the brake fluid in the system, entirely. Because there is fluid in it, this includes the ABS module.
All service manuals assume the user has mechanical ability and knowlege. If it were written with every instruction imaginable it would be as thick as that book on how to understand women.
Last edited by 702; Feb 22, 2023 at 09:08 AM.
Seasoned HDF Member
Joined: May 2018
Posts: 5,814
Likes: 7,142
From: Las Vegas
The brake system INCLUDES the ABS module.
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Seasoned HDF Member
Joined: Sep 2017
Posts: 12,186
Likes: 4,908
From: England
Sometimes you have to be meticulously verbose such that nothing is left to chance or be misconstrued. 
On my bike air hasn't got into the system over the 2 years before the fluid has been flushed. In the UK the price for flushing the system is negligible and is part of the 2 year service pattern when doing less than 5k miles a year.
On my bike air hasn't got into the system over the 2 years before the fluid has been flushed. In the UK the price for flushing the system is negligible and is part of the 2 year service pattern when doing less than 5k miles a year.
Last edited by Andy from Sandy; Feb 22, 2023 at 08:50 AM.
Thread Starter
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Cruiser
Joined: May 2022
Posts: 131
Likes: 64
From: Cleveland
This just has me rethinking my neglect of the fluid in the abs unit on my other vehicles.