Brake fluid flush and colors

[JFENG]

I flushed the entire brake system. The fluid in the reservoir was like strong tea so I suctioned it out to avoid pushing it thru the rest of the system.

Then I bled the lines with a very old Bav Auto pressure bleeder. I also put a vacuum bleeder on the nipples because it has a large waste fluid container that can do a couple car’s before needing emptying. Plus, the vacuum prevents leaks at the nipple keeping everything nice and clean.

Anyway, here is my point: The PO used a mechanic who alternated brake fluid colors on each flush to make it easier to tell when the new fluid had reached each caliper. What was in the system was faint blue Motul. The fluid I got out of each caliper had not darkened at as far as I could tell. I suspect I might be ok changing the fluid in the reservoir every two years and the lines/calipers every 4 years if I don’t drive it.

 

[deQuincey]

i too did use alternatively blue and yellow ate fluid,
but blue is NLA
we discussed it here, some brilliant guys decided to ban the use of blue, so we can only go through different grades of yellow

 

[deQuincey]

I flushed the entire brake system. The fluid in the reservoir was like strong tea so I suctioned it out to avoid pushing it thru the rest of the system.

Then I bled the lines with a very old Bav Auto pressure bleeder. I also put a vacuum bleeder on the nipples because it has a large waste fluid container that can do a couple car’s before needing emptying. Plus, the vacuum prevents leaks at the nipple keeping everything nice and clean.

Anyway, here is my point: The PO used a mechanic who alternated brake fluid colors on each flush to make it easier to tell when the new fluid had reached each caliper. What was in the system was faint blue Motul. The fluid I got out of each caliper had not darkened at as far as I could tell. I suspect I might be ok changing the fluid in the reservoir every two years and the lines/calipers every 4 years if I don’t drive it.

I suspect I might be ok changing the fluid in the reservoir every two years and the lines/calipers every 4 years ...



i would not recommend this,
considering that 1-the theoretical period change for the whole fluid is one year
2-the fluid circulates so you have the same stuff in the reservoir and in the lines
i would say, make it 2 years and do it complete

 

[adawil2002]

Buy a Brake Fluid Tester from either an auto parts supplier or choose one of the several available on amazon. Take the guess work out of the equation. Moisture content should be below -3% if 3%+ or above change. There's a whole thread on routine maintenance & intervals.

 

[JFENG]

the fluid circulates...

Based on my experience with my few classic cars this partially true, and the degree of circulation is partly dependent on usage.

The fluid in the reservoir seems always much more contaminated (darker) than the fluid in the lines and calipers on my cars. This was certainly true on my E9 last night. Maybe it’s because the caliper seals were replaced 16 years ago?

I should have saved separate samples of the old fluid from the reservoir and calipers to test but unfortunately I put all of it into the same waste bottle. I will do this on the next fluid change. On older cars the reservoir is vented directly to the atmosphere and is therefore the point of highest moisture contamination. The risk at the caliper, AFAIK, is also copper contamination (IDK where it comes from). Supposedly there is a NHTS study saying that copper contamination related brake failure dominates water based failures. I’ve not seen the actual report. Anyway, testers for copper and water contamination are inexpensive And give us amateurs a way to perform maintenance based on data rather than standard assumptions. Test strips


Well, I left me step back by saying flushing the hydraulic system every1 or 2 years is a very safe assumption, and you won’t go wrong with this schedule. As an engineer, I’d like to know enough to functionally justify my maintenance schedules.

 

[bavbob]

What to do with the old fluid. I don't know any place for recycling. This is what stops me from such frequent changes.

 

[Luis A.]

What to do with the old fluid. I don't know any place for recycling. This is what stops me from such frequent changes.

For me, the same place I take my waste oil.

 

[JFENG]

For me, the same place I take my waste oil.

I’m sending you a gift package....

 

[bavbob]

They usually let me in the back to dump my oil, no other receptacle there.

John, just bring it by, then you take take all the images you want of the seat platform.

 

[JFENG]

Bob, hope you know what you’re getting into. . . DQ has me going wild with hydraulic fluid flushes.

 

[Cornishman]

When I do my flush I just one rear caliper and pump a couple of reservoirs worth through, then move onto the other calipers and do about half a reservoir worth for each. This ends up about 1.5 litres for each flush. Just need to be careful to not let the reservoir run empty.
Is this 2 litres what the experts find is about correct?

The first time I did this the brake system was empty so to get rid of the air took about 2 litres, plus some swearing and final advice from SF Don. Bleed until I got a reasonable brake pedal, drive it for a week, then do it again.

 

[JFENG]

I used about 1 liter yesterday. But consider my pads are thick so there is not a lot of fluid inside the calipers. I bled till the color change was complete. The clutch will take another 1/4 liter at the most. 2 liters seems like a lot.

 

[Cornishman]

Thanks bfeng, mine is RHD so the brakes are a PITA to get the air out, 2 services etc.
I always find the clutch difficult to flush, but to bleed it just seems to do itself. However, fully agree it is necessary to flush that out also. The first time I did that something like vintage sump oil came out, so yes the master and slave were soon history when I drove the car

 

[JFENG]

Get a cheap pressure bleeder and a cheap vacuum unit. When I use both together I believe I can bleed anything....

My pressure bleeder can hold brake fluid in the pressure vessel, so you don’t run the reservoir empty on a long bleeding session. This makes it easier to fill a system that has been totally drained.

 

[deQuincey]

Get a cheap pressure bleeder and a cheap vacuum unit. When I use both together I believe I can bleed anything....

My pressure bleeder can hold brake fluid in the pressure vessel, so you don’t run the reservoir empty on a long bleeding session. This makes it easier to fill a system that has been totally drained.

all you said is good

+add a compensation bottle to your bleeding equipment, essentially, a big bottle that can hold 1 liter of fresh fluid, with a narrow mouth, put it upside down into your reservoir and let the needed fluid fall as required, it is not magic it is physics

 

[deQuincey]

Get a cheap pressure bleeder and a cheap vacuum unit. When I use both together I believe I can bleed anything....

My pressure bleeder can hold brake fluid in the pressure vessel, so you don’t run the reservoir empty on a long bleeding session. This makes it easier to fill a system that has been totally drained.

Lan-Engine M30B30 Maintenance thread. Periods, products, processes,...tips and FAQs

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e9coupe.com

#19

When I do my flush I just one rear caliper and pump a couple of reservoirs worth through, then move onto the other calipers and do about half a reservoir worth for each. This ends up about 1.5 litres for each flush. Just need to be careful to not let the reservoir run empty.
Is this 2 litres what the experts find is about correct?

The first time I did this the brake system was empty so to get rid of the air took about 2 litres, plus some swearing and final advice from SF Don. Bleed until I got a reasonable brake pedal, drive it for a week, then do it again.

found that to do the complete 5 ends, 4 wheels + 1 clutch i need 1,5 liters

 

[Cornishman]

DeQ, thanks for the confirmation re volume to flush.
I have had a look at your suggestion above with the feed to the reservoir.
What stops the fluid in the 1 litre bottle all going into the reservoir until it overflows, whilst still enabling enough fluid to go into the reservoir to keep the reservoir full?
What is the device that goes from the 1 litre bottle up to the hood bracket, is that an air valve to allow air into the 1 litre bottle thereby letting the fluid out? If so, do you have to manually control it?

 

[Honolulu]

Holdonaminnit. Brake fluid simply pulses back and forth in the M/C, lines and calipers. It doesn't, strictly speaking, "circulate". Blood circulates in that it passes through separate pipes outbound from you heart, through your system, and then back to the heart via different pipes. At least mine I think mine does...

I think if one sucks out the contents of the M/C reservoir before adding new fluid, you can get a 4-wheel brake flush with 1 liter. It would help to have each caliper piston fully retracted first, to push the maximum amount of fluid back into the reservoir, but if fluid is sold by the liter, use it all and don't keep any to go stale on the shelf.

 

[deQuincey]

DeQ, thanks for the confirmation re volume to flush.
I have had a look at your suggestion above with the feed to the reservoir.
What stops the fluid in the 1 litre bottle all going into the reservoir until it overflows, whilst still enabling enough fluid to go into the reservoir to keep the reservoir full?
What is the device that goes from the 1 litre bottle up to the hood bracket, is that an air valve to allow air into the 1 litre bottle thereby letting the fluid out? If so, do you have to manually control it?

what stops the fluid to go and splash into the reservoir until overflows is the famous principle of the water drinking bottles for ducks, probably there is a tedious name of a scientist, but believe me it is the duck drinking bottle principle, aka, from now on the dQ principle.

so esentially, if you put an open bottle full of a fluid upside down inside an empty glas, or cup, the fluid will go out from the bottle and start filling the glass, but the fluid will stop falling in the very moment the rising fluid touches the mouth of the bottle

hence when you hang this brake fluid bottle upside down you have to touch the surface of the brake fluid in the reservoir, then when you start bleeding you will suction some fluid through the lines, and the level in the reservoir will decrease, this will force more fluid to come from the bottle to level the reservoir

tha "device" that goes from the bottle to the hood bracket is a rope with a hook to keep the bottle vertical

ducks are clever animals, they drink water in a very educated manner

hope it is now clear, no magic, simple physics

regards

 

[deQuincey]

Holdonaminnit. Brake fluid simply pulses back and forth in the M/C, lines and calipers. It doesn't, strictly speaking, "circulate". Blood circulates in that it passes through separate pipes outbound from you heart, through your system, and then back to the heart via different pipes. At least mine I think mine does...

I think if one sucks out the contents of the M/C reservoir before adding new fluid, you can get a 4-wheel brake flush with 1 liter. It would help to have each caliper piston fully retracted first, to push the maximum amount of fluid back into the reservoir, but if fluid is sold by the liter, use it all and don't keep any to go stale on the shelf.

i am holding my breath now...

brake fluid circulates, not in a perfect rotational manner, but those pulses are not perfect, so sometimes more comes than goes, sometimes it is the opposite, proof, i have found dirty deposits in my reservoir, where do they come from ?

as to the 1 litre bottle, yes, it is advisable to use all to circulate and clean the lines, it makes no sense to keep it in the shelf, it will be degradated when you try to use it.
and i do not remove the old fluid, i simply let new fluid pass through the lines until i finish my compensation bottle, that is my trick, i fill the compensation bottle and i use it all

regards