Changing the Brake Fluid

[ORRadtech]

I did it.

The biggest problem was that it was really hard to tell when fresh fluid was coming through the tube. The old fluid wasn't that dirty. It was light yellow, while the new one was just a sliiiightly lighter shade of yellow. There was no clear-cut separation between them as they came out of the caliper. So I was just sitting there staring at it, wondering if it really was a tad lighter than it had been at first, or it was just my imagination. In the end, seeing that the catch can was beginning to fill up, I decided that it must be clean already and moved to the next wheel. And indeed, as soon as I opened the next bleeding nipple I noticed a tiny difference.

After bleeding each rear caliper I pulled and released the handbrake five times, then opened the screw again for a few seconds. No air bubbles came out.

Two things.
Flushing shouldn't produce bubbles, the system wasn't opened.

Did you notice any difference/ improvement in stopping or pedal feel.

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[Vlad Soare]

Flushing shouldn't produce bubbles, the system wasn't opened.

True. Then what’s the purpose of pulling and releasing the handbrake five times, I wonder? Will it expel some extra fluid that would have otherwise remained in the system? The service manual advises to do that but doesn’t say why.

Did you notice any difference/ improvement in stopping or pedal feel

No, no difference whatsoever. Everything feels exactly the same. Granted, the old fluid was still in good shape, so an obvious improvement would have been quite unlikely. I’m glad I can’t perceive any difference for the worse, though. It gives me confidence that I did it right.

 

[ORRadtech]

True. Then what’s the purpose of pulling and releasing the handbrake five times, I wonder? Will it expel some extra fluid that would have otherwise remained in the system? The service manual advises to do that but doesn’t say why.

Well, if it's capable of having bubbles the it has fluid so working the lever would(should?) Move old fluid out.

No, no difference whatsoever. Everything feels exactly the same. Granted, the old fluid was still in good shape, so an obvious improvement would have been quite unlikely. I’m glad I can’t perceive any difference for the worse, though. It gives me confidence that I did it right.

Thanks for that. I wouldn't expect to notice a difference but???

One more question. Did you happen to check the fluid for moisture content before you flushed it?

 

[Vlad Soare]

Did you happen to check the fluid for moisture content before you flushed it?

Yes. It showed yellow (less than 1%) in the reservoir, before starting the flush. Then I tested it again in the catch can at the end, and the indication oscillated between yellow and green (I guess it was mixed with a bit of fresh fluid, because I had bleeded the first wheel a bit too long - hence the very slight improvement).
This was after three years and 14K miles.
I should have changed it one year ago according to the manual, but somehow I didn't get around to doing it at the time, and then I tested it and it showed green, so I postponed it a bit.

My wife's Kuga is showing yellow after only 1.5 years and about the same mileage. Which makes me think that mileage has a more pronounced effect on its aging that time.

 

[Vlad Soare]

Most of you are probably aware of this trick, but I wasn't, and I discovered it myself after quite a lot of head scratching and swearing. How are you supposed to check the fluid level in an opaque container?

No idea where the actual level is. The reservoir could very well be empty.
Removing the cap and looking down the filling neck doesn't help either, because the only thing you can see in there is just a small hole, not the actual space where the bulk of the fluid is.

In the end I tried to shine a flashlight through the side of the reservoir opposite to where I was looking, and voilá! A portion of the right hand side wall is slightly more transparent than the rest (which otherwise you wouldn't have noticed), and the brake fluid can now be clearly seen.

 

[GTP]

I just wiggle the reservoir a little to see the fluid moving.
Hardest to tell when the level is right at that seam.

 

[Biggsy]

In the end I tried to shine a flashlight through the side of the reservoir opposite to where I was looking, and voilá! A portion of the right hand side wall is slightly more transparent than the rest (which otherwise you wouldn't have noticed), and the brake fluid can now be clearly seen.

I only learned this trick after 100s of brake bleeds lol and it was by accident. my helper had a flashlight and sat it on the reservoir. Shining the light from the top pointed down allowed me to see the fluid level clear as day.

 

[WItoTX]

I bled my brakes at night, and discovered that trick on attempt #1. Accidentally.

 

[BlueThunder16]

Read through this thread as I'm getting ready to do a flush on my car. Just wanted to double-check the process since I've bled brakes on other cars before, but not an S550.

I'm pretty sure I didn't see anyone bring it up yet, and maybe it's a silly question. But is any consideration given to the clutch during this whole process, since they share the same reservoir and fluid?

 

[Vlad Soare]

See here:

https://www.mustang6g.com/forums/threads/replacing-clutch-fluid.181642/

Long story short, don't worry about it.

 

[gfcobra04]

Be careful topping off your brake fluid reservoir. If you track your car at all, you do not want to fill the brake reservoir up to the max. It will overflow due to the heat and the G forces on turning.

you can always use a syringe to suck out fluid from the reservoir if you need to.

 

[GTP]

Be careful topping off your brake fluid reservoir. If you track your car at all, you do not want to fill the brake reservoir up to the max. It will overflow due to the heat and the G forces on turning.

you can always use a syringe to suck out fluid from the reservoir if you need to.

Has that happened to you?

I'm concerned about the level at minimum on track because G forces causing the bottom hole to be exposed to air.

 

[gfcobra04]

Yes, this has happened to me with my 2000R. The supposed fix was to just take a rag and wrap around it with a zip tie and then just remove the rag and replace it. I’m not talking about a lot of fluid but fluid does seep out of the brake reservoir.

The brake fluid will expand over a track session because of the heat generated in the engine compartment and that includes all your fluids oil, transmission, radiator. The oil in my 2020 GT 500 expands considerably over one session. In fact in my GT 500 when the oil expands, its measures around a quarter to half a quart more fluid on the dipstick. I have not been able to duplicate this thermal expansion in the oil by driving on the street no matter how hard I push the car.

 

[Vlad Soare]

I've just noticed something.
The instructions for my pressure bleeder state that I should not exceed 28 psi.

On the pressure indicator the red zone starts at 32 psi.

However, here's what the service manual says:

Why do they recommend such a high pressure? 20 psi worked just fine for me.
Does this have to do with the valves in the ABS module? Do you need higher pressures to open them up?

 

[GTP]

I pump up to 30psi, empty tank. Works fine, no issues. $0.02.

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