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Question about brake fluid changes + mystery wires

532 Views 11 Replies 8 Participants Last post by  DanaH
Hi there, i have 2 questions. The first is one I haven't seen asked in this forum (though I'm sure someone better at searching could find something), the second is a question I've seen asked but get contradictory responses.

Question 1: What are these wires on the brake fluid cap (circled below), and do they need to be connected to anything?

Font Circle Auto part Drawing Diagram


It kind of looks like they could mate with these others wires (see photo below). I'm trying to figure out whether I accidentally separated them without noticing while unscrewing the cap:
Automotive tire Motor vehicle Tread Fender Hood




Question 2: Why can't I just do the equivalent of a drain + fill of the brake fluid in the master cylinder, without bleeding the brake lines?

Some people say you need to bleed the brakes because there's no circulation in the brake lines, so the new stuff wouldn't actually mix. Other people say water sinks to the bottom of the lines and that's what you really need to get out.

Why, if there is no circulation in the brake lines, does the fluid in the master cylinder dirty over time? If there really is no circulation than it should stay clear, no?. That doesn't make sense to me. The water point I have no argument against, seems sound if that's actually what water does in a brake line. As you can probably guess I'm just trying to avoid removing my wheels and bleeding the lines because I rent and have no driveway/limited tools.

Thanks for the help!
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Question 1 see above.
Question 2 brake fluid is hydroscopic and absorbs water just like a sponge.
Get a one way check valve in the picture and you can replace the fluid by yourself.
Just hook this device up, arrow on it points to the jar or bottle that the used fluid is going into and pump away on your brake pedal and fill your reservoir up.
Tip: Use a turkey baster type tool to suck out the old fluid from the master cylinder. Add fresh fluid from an unopened bottle of DOT 4. Then your sending fresh fluid into the lines and secondary cylinders.
Never let it run dry, if you do, take it in and get it professionally bled.

Motion pro brake bleeder check valve
Font Auto part Rim Metal Engineering
 

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Discussion Starter · #5 ·
1 - Those wires to indicate low brake fluid
2 - Bleed the brakes. Even if you're parked on the street. Park in low-traffic area and do it. If you have some one to assist you, great, if not, buy speed bleeders and you can bleed the brakes solo.
Do the wires attach to the other wires? The repair manual doesn’t mention anything about it but it sure looks like they should.
 

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Of course the fluid in the reservoir on top mixes with the fluid in brake lines over time. It is just you can only remove a limited amount of fluid from the top. My guess it is less than a 1/4 you can remove from the top without risking introducing air in the system.

I don’t know if it is true that water tends to accumulate at the lowest point and not mix with the rest of the fluid. There are testers that you stick In the brake fluid reservoir to measure water content in the fluid to determine if the fluid is good. If water accumulated only at the bottom these testers would be pointless.
 

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Paintbucketbrush,
The fluid, should be clear/amberish in the master cylinder. If's darker, bleed the system. if you didn't change fluid in the last 5 years, bleed the system, too. if the brake pedal spongy, bleed it...
Please note, that bleeder screws could be rusty and there's a possibility to strip the heads. Purchase 4 new bleeder screws locally, or speed bleeders online (i doubt that auto parts store would carry proper speed bleeders for Honda).
Note: see if you can turn cap 180 degrees, so the wire connectors are closer to each other.

There are testers that you stick In the brake fluid
Easier/cheaper to bleed the system... Unless you have many old cars.
 

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Hi there, i have 2 questions. The first is one I haven't seen asked in this forum (though I'm sure someone better at searching could find something), the second is a question I've seen asked but get contradictory responses.
Why, if there is no circulation in the brake lines, does the fluid in the master cylinder dirty over time? If there really is no circulation than it should stay clear, no?. That doesn't make sense to me. The water point I have no argument against, seems sound if that's actually what water does in a brake line. As you can probably guess I'm just trying to avoid removing my wheels and bleeding the lines because I rent and have no driveway/limited tools.
Here's the scoop. Connect those wires! Male to female. Binary genders.
Brake Fluid (Use Dot 3) is hygroscopic. It deteriorates inside the Master Cylinder by absorbing moisture from the air. The Brake Fluid and water do not "separate." The brake fluid also deteriorates at each brake cylinder. It turns black due to use and heat. For both reasons, the fluid deteriorates over time and needs replacement.

The normal way to bleed is to suction out the master cylinder and replace with new fluid from unopened container. Then bleed the rear brake cylinders. Keep adding fresh fluid in the master cylinder. Never allow the master cylinder to empty. Then bleed the front brakes, adding more fluid to the master cylinder.
 

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…..also deteriorates at each brake cylinder.
This is more commonly called a brake caliper, found at each wheel. There is only one brake master cylinder found under the hood below the brake MC reservoir.

Here's the scoop. Connect those wires! Male to female. Binary genders.
Brake Fluid (Use Dot 3) is hygroscopic. It deteriorates inside the Master Cylinder by absorbing moisture from the air. The Brake Fluid and water do not "separate." The brake fluid also deteriorates at each brake cylinder. It turns black due to use and heat. For both reasons, the fluid deteriorates over time and needs replacement.

The normal way to bleed is to suction out the master cylinder and replace with new fluid from unopened container. Then bleed the rear brake cylinders. Keep adding fresh fluid in the master cylinder. Never allow the master cylinder to empty. Then bleed the front brakes, adding more fluid to the master cylinder.
 
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