Fed brake MC fluid flush in situ PROBLEM

[tedtaylor]

i'm going over brake system and attempting to flush the brake fluid, however upon sucking out the old fluid from the master cylinder in situ, there appears to be a rear most compartment (where fluid level sensor mounts) that I cannot get to in order to clean/flush/ or suck out. The baffle wall seals the whole compartment and is holding back about an inch deep of old dirty fluid. I'm trying to keep everything in place without MC removal to ease my overall operation.
any suggestion or procedure on what to do with that compartment???

I did pry off the top black plastic cap to the fluid sensor (which fell into the engine area !!! fun, fun, …. I did find it eventually), however pulling up the wire and sensor it is a computer board with diodes and only comes up so far and hits the wiper arm area. I can't pull it out in situ, but decided I probably shouldn't since this computer board is not exposed to the fluid. Must be a bigger plastic tube it sits down in?

Please advise what to do.
thanks!!!

[Brit-Car-Nut]

Ted,

Can you stuff the reservoir with a clean shop rag? Use it like a sponge and let it soak up the old and then carefully remove the rag into a plastic bag so you don't contaminate the engine bay or the paint work. Do it a little bit at a time and then top it up with fresh fluid.

You could also put fresh fluid in the reservoir and use an EZ-Bleed to push the fluid thru the system one caliper at a time. That replaces ALL of the fluid, not just what is in the reservoir.

https://www.ebay.com/itm/Gunson-EEZIBLE ... Sw58VamTYy

[steve matthews]

Ted, geta power bleeder and bleed the entire system. If this dark fluid is in the reservoir its also in the rear proportioning valves.

[tedtaylor]

Steve & John, thanks for responding. This issue is not bleeding or cleanliness of the reservoir, it is that little hidden inaccessible compartment at the rear most part of the reservoir that still holds a half inch of dirty fluid. I have sucked out the rest of the reservoir bone dry and cleaned with rag. I will be flushing entire system with new fluid, but at the worst right now, that old inaccessible dirty fluid will mix with the new I put in.
I was able to move the wiper arm enough to pull the circuit board low level sensor out of the top, however I don't think brake fluid fills that little tube? or does it? is the sensor an optical (without touching fluid) or contact one (that does interact directly with fluid)???

I stuck a bleeder tube down that hole where the sensor came out, but it doesn't seem to go down far enough into the fluid and thus my question above.

[steve matthews]

Ted, will be at shop tomorrow and look at the reservoir.

[Brit-Car-Nut]

After looking at my master cylinder, I realize what you are asking.

You can NOT drain the rear chamber easily.

OBVIOUSLY, you need to do everything you can to prevent the brake fluid from getting anywhere on the paint. Use LOTS of towels at the BMC to capture the brake fluid.

DO NOT USE HIGH PRESSURE TO BLEED THE BRAKES You could push some gunk into the proportioning valves.

I have a pressure bleeder as well as a few EZ Bleed kits, so I can bleed brakes by myself.

Each BMC chamber services one front and one rear caliper (or so I was told).

If you have a helper, just put fresh fluid in the now empty chamber and pedal bleed the FRONT brakes FIRST. You should see the fluid level go down in one of the chambers as you bleed a front brake. If the front chamber goes down first, switch to the other front caliper and use it to push the old fluid out until you see the dark fluid come out. It sounds wrong, but you want to push the bad fluid out without pushing it through the proportioning valves. When you have pushed the dark fluid out the front bleeders (you will see it in the bleed tube), start again and do the rears first and then the fronts.

If you have a low pressure bleeder, do the same thing but you won't have to open and close the bleeder as the helper "pumps up" the system.

[tedtaylor]

i'm tempted to use a long drill bit and drill a hole in the inner wall side of that rearmost chamber. then the fluid will drain forward and allow me to suck it all out.
I can't understand the reason behind this design which allows old fluid to congregate and not be drained/cleaned out.

[Brit-Car-Nut]

That is probably not a great idea.

The chambers are separated or isolated so that if one wheel cylinder, hose or line fails, you will only lose 50% of the braking capacity. If you "merge" the tow chambers, then ALL of the brake fluid can go out the bad wheel cylinder, hose or line.

[tedtaylor]

I hear you, but isn't that what the low fluid sensor is all about? if fluid loss, the warning light on the dash would come on.

Looking at the inner plastic dividing wall, it appears to be two pieces. I could understand leaving/having the lower wall section, but there should be no reason for the upper half of the wall. The fluid would spread between front and rear sections only so much and leave a "reserve" amount at the half way point. That way, without the top section, one could get a siphon hose in that rearmost compartment to suck out the old fluid and better clean it up.

Why am I trying to redesign what should already be factored in with the original design????

[tedtaylor]

well just to close this post out, I have completed the brake job successfully and i'm very pleased. In the end, I was unable to get to that back little compartment in the MC with it in situ, so I could only dilute it with new fluid and flush the system. Very disappointed with the design.

I ran into a problem (my lack of knowledge/experience) with the rear calipers and that funky E-brake ratcheting the piston further out. I kept trying to push the piston back in with a large C-clamp without success and almost ruined the seals/boot with a close call nearly hyper extending the piston out of the caliper completely, however I read the shop manual and quickly learned the trick to turn the puck counter clockwise (right rear) and it retracts. DUH!!!! Didn't have the special brake tool, but was just as successful with a flat blade screw driver turning it back in.

all my sliding pins were in perfect smooth working order, moving in and out with ease!

I power bled the whole system initially, then had wife pump brakes on final go-around. All clear clean fluid coming out all four corners. Fresh new pads. Test drove and brakes feel good, no squeals, no pulling, excellent feel.

I also put on a new set of Bridgestone Comp 2TA tires. Drives like a dream, quiet, smooth. Amazing how a new set of tires can make a very big difference on ride, feel, sound, etc. The car drives like brand new, so i'm very pleased!

[HJ2]

I hear you, but isn't that what the low fluid sensor is all about?

What good is a brake warning light triggered by the sensor, if all the fluid’s gone in BOTH circuits ?!

Anyway, job well done!

[Simon_P]

Too late for you and I don't know about the LHD m/c, but the RHD m/C has a plastic reservoir which can be removed.

[Brit-Car-Nut]

They ALL have removable reservoirs but on the LHD car EVERYTHING that can be a pain in the arse (ICM, Coils, Coolant Tank) is in that near side corner of the engine bay. It would be a true mess if you pulled it without emptying it.