Brake fluid Black-ish in reservoir - should it be clear?

[PINBALL]

Brakes A1, but reservoir bottle shows fluid as dark almost black.

How does it get dirty?

Or is it meant to turn this shade when air / age has corrupted fluid?

Should I be concerned & get the system flushed before damage occurs with cylinder seals?

As always your comment are appreciated.

Keith.

 

[Myros]

new fluid

looks golden or brown in the reservoir. The blackness is due to absorbed dirt and moisture from the atmosphere. Wise to have it replaced every 2 years or so any way, as it will have absorbed enough moisture by then to make it more prone to fading in extreme conditions.

 

[TimN]

I think that a chemist could tell you about the chemical reaction that occurs because of the contact of the fluid with rubbers and different metals in the breaking system. The build up of the brake fluid include inhibitors to minimise the effects. It is recommended that brake fluid is changed every two years. If you are going to do this then remove as much as you can from the reservoir. I use a hydrometer as a syringe. Then top up with new and start working through the system starting with the brake furthest away from the reservoir towards the closest to it.

 

[MW]

It really should be light yellow in colour. After about 2 years it will darken. Compare new and 2 year old fluid. The problems will arise if it is not changed regularly. Most important is the ABS pump which is about £1000 if it fails due to corrosion etc etc. Also calipers will fail if in contact with hydrscopic fluid. The peddle may also go spongy as the fluid aborbs water.
I change mine every 18-22 months. The fluid (you need a litre) is only £4 -50p in Wilkinsons. Amazingly cheap compared to the ABS pump.
I have used an Easibleed kit for years and it works wonderfully well. I would pump just air through first and blow out the old fluid. Then double bleed through. Maybe use a litre and a half of fluid and have a really good flush through. I also put a tiny tiny smeer of copper grease on the brake nipple threads. Barely any, to avoid contamination, but enough to stop corrosion and a sticking bleed nipple. The whole job should cost a fiver and take just over an hour.

 

[Ramius]

Couldnt agree more with the sugestions here already. Like ATF fluid....Colour is a clue to age and/or issues.

 

[paulcallender]

I didn't know you could bleed the entire system with air first of all, to guarantee all the old fluid is out, then refill with brake fluid. Handy to know for the future! By sheer chance, I bled my brakes and changed the fluid today, too. I found out the hard way that the 20psi limit really is a limit, becuase at 30psi or so (of the tyre originally), the Easibleed cap explosively detached from the fluid reservoir and sprayed the engine bay with brake fluid! Oops....

Also, I think mine is past its best, it hisses and I guess this is whats responsible for flattening the tyre, on one bottle of fluid (I needed around 5-6 bottles of it in the end). But, my local Halfords don't sell them any more.

 

[MW]

Thats interesting as I have often wondered how sentitive the 20 lbs limit was.
I like blowing air through really to avoid putting new fluid 'on top of' old fluid. It must get mixed and contaminated.
The hissing sound could be a leaky rubber seal. The Easibleed screw-on cap is a little tempremental. Try picking the seal out, and turning it over. I am surprised you used so much fluid, as one benifit of Easibleed is that I find I can bleed the system all round twice easily, with a litre of fluid.

 

[woodturner-fran]

The WIS DVD gives this method for changing the fluid if you don't have the equipment:

Empty brake reservoir as best you can.
Refill with new fluid.
Start with wheels at back and open bleed screw. Pump pedal 8-10 times. If no air is coming through and flow is clear, lock up the bleed screw and move on.
Keep an eye on the fluid reservoir and top up as needed.

For my W210 they talk about 0.6L, but would be wise to have more on standby esp when its so cheap

Fran

 

[davidsl500]

The WIS DVD gives this method for changing the fluid if you don't have the equipment:

Empty brake reservoir as best you can.
Refill with new fluid.
Start with wheels at back and open bleed screw. Pump pedal 8-10 times. If no air is coming through and flow is clear, lock up the bleed screw and move on.
Keep an eye on the fluid reservoir and top up as needed.

For my W210 they talk about 0.6L, but would be wise to have more on standby esp when its so cheap

Fran

I wouldnt recommend anyone trying this - open bleed screw and pump pedal ? - surely you will be pulling in air every time you release the brake pedal?

 

[paulcallender]

I've always done it with a combination of 2 kits. A one-way valve and tubing on the bleed nipple, and an Easibleed kit on the fluid reservoir. This way, one person can observe the fluid flow at the brake nipple end, thus ensuring no air bubbles remain.

 

[MW]

If you are using Easibleed, why use a one way valve as the fluid can only go one way...i.e. outwards? It can never go backwards.
I agree the above bleeding method would suck in air. Many years ago I use to have a terrible job bleeding brakes, with all the usual equipement, jamjars etc. All was solved when a mechanic told me that if bleeding manually, you must close the bleed nipple on the peddle upstroke, regardless of what valve system you are using (except Easibleed). This is because air gets sucked back into the systen via the bleed brake nipple threads.
It's really true, and works. So, if you are working conventionally the sequence is....
open, peddle down, close, peddle up, open, peddle down, close, peddle up etc etc.
It really works, and saves using too much fluid.

 

[paulcallender]

If you are using Easibleed, why use a one way valve as the fluid can only go one way...i.e. outwards? It can never go backwards.

.....Because, the Easibleed provides a remote, continious way to keep brake fluid flowing towards the caliper (and out the nipple), therefore you can stay near the caliper and observe the air coming out, also looking closely at how dark/light the fluid is, which will give a vague indiction of when you've expelled the old fluid and the system is full of new fluid.

I agree too, the above procedure must have missed out a few steps. With the (obvious) step of closing the bleed nipple before the assistant brings up the brake pedal, it would be effective too. But, requires 2 people and is prone to error.

Of course, the best way to bleed brakes is to use a vacuum kit which attaches to the bleed nipple and does not require the pressurisation with air, of the top of the reservoir. This would have avoided my indident when the Easibleed cap blew off!