Removing Break Fluid from Bn6

[BN6_2197]

As posted in another thread I have to replace one of my wheel cylinders of the front brake of my BN6. For this I want to remove the break fluid from the break system. Can anybody advise me on the correct procedure? I only found the way of correct bleeding in the workshop manual.

Volker

 

[steveg]

Volker,
You can use one of these to pinch the flex hose so the fluid doesn't leak out when you're doing the repair. You can also seal the vent in the reservoir cap with tape. That way you don't have to remove the fluid.
Update: a kitchen basting bulb-syringe is an inexpensive way to remove the fluid from the reservoirs.

 

[blueskies]

I agree with Steve. Unless you want to also change out all the brake fluid, you should not lose that much when replacing a wheel cylinder. It does not take long to bleed the air out of the system. Even though it might not be necessary, I might bleed the brakes at all four wheels after working on the system in order to get any air out.

 

[TimK]

Fluid should be changed. Start by suctioning out the fluid from the reservoir. Then open each bleed valve starting with the right rear wheel and have a helper pump the brakes to push out the fluid. Then do the left rear, right front, left front. Do your brake fix, then refill the reservoir with new fluid and bleed the system starting with the right rear, then left rear, right front, left front. Make sure to refill the reservoir after each wheel to make sure you don't allow air to re-enter the system.

 

[HealeyRick]

Fluid should be changed. Start by suctioning out the fluid from the reservoir. Then open each bleed valve starting with the right rear wheel and have a helper pump the brakes to push out the fluid. Then do the left rear, right front, left front. Do your brake fix, then refill the reservoir with new fluid and bleed the system starting with the right rear, then left rear, right front, left front. Make sure to refill the reservoir after each wheel to make sure you don't allow air to re-enter the system.

Tim,

I don't think your brake bleed sequence is correct for a LHD BN-6. The brake bleed sequence is usually described as bleeding from the farthest wheel away from the master cylinder to the closest wheel to the master cylinder which is the sequence you've described. It more accurately should be described as the wheel with the longest pipe run from the master cylinder to the one with the shortest. If you look at the diagram of the pipe runs of the 100-6:

You'll see the longest pipe run goes to the left rear, then the right rear, then the left front, then the right front. I spent years doing it the way you described until Rich Chrysler pointed out the correct way.

 

[TimK]

Thanks for the correction, I assumed a BN6 was the same as BN7. While trying to be helpful, sometimes I exceed my actual level of knowledge. It's good there are so many experts on the lookout.

 

[steveg]

Looking at the Moss diagrams, it looks like the left rear is the longest run on all models. Would guess the RHD models would be the same except for a shorter run from the MC to the 5-way union.

 

[HealeyRick]

Tim,

I think the BN7 has the same layout of the BN6. I think a lot of us started working on American cars where the brake pipe travels to the rear down the left side of the car, which makes your sequence of bleeding correct.

 

[John Turney]

....
Update: a kitchen basting bulb-syringe is an inexpensive way to remove the fluid from the reservoirs.

Just don't use it for the turkey afterward.

 

[HealeyRick]

Just don't use it for the turkey afterward.

Don't knock it until you've tried my special DOT4 gravy.

 

[Bob_Spidell]

I just used one of these to extract oil from a lawnmower:

https://preview.tinyurl.com/kuxsmek

Would work well for removing brake fluid, too (but I have a plastic syringe as well).

 

[blueskies]

Fluid should be changed.

That depends on when it was last changed.

 

[BN6_2197]

Gents, I want to replace the brake fluid in the context of repairing my cylinder since the fluid is more than 5 years old. I have heard that the fluid should be changed on regular basis to to water that might mix with the fluid. By this reducing the power of the brakes.

Concerning the fluid push out sequence: is this the same as the bleed sequence Rick mentioned. So far I understood that the blee sequence is typically the sequence to refill the fluid into the system.

Concerning the tools:
* What tool do you use typically to suction the fluid from the reservoir? Can I use a bigger medical injection for this?
* Tim mentioned a "helper pump" to push the fluid out of the blee valeves: is there any available in a shop or did you handcraft it yourself?

Unfortunately the tiny URL of Bob's post does not work.

 

[Bob_Spidell]

...
Unfortunately the tiny URL of Bob's post does not work.

It works, just takes you to TinyURL so you can see the link before clicking on it. Here's a non-preview link:

https://tinyurl.com/kw6jlpb

Not cheap, but comes in handy now and then (I just used it to change lawnmower oil; lot easier than turning mower on its side).