Series 3 BLEEDING BLINKIN' 109 BRAKES

ciderman · Mar 27, 2019

Is it just us - or is it everyone who has so much difficulty bleeding the rakes on 109?
3 of us with a sealey pro brake bleeding kit spent a day and a half trying to get a good pedal.
between us we had 142 years of experience- yet we still struggled and did it time after time until exhaustion set in and a half decent pedal was achieved.
Who knows the secret?

tottot · Mar 27, 2019

When I had a 109 I changed the set up on the front 2 slave brakes. As standard flexi goes to top slave and a hard pipe then takes fluid to the bottom slave, air likes to stay at the top.
So I swopped pipes over. The flexi stays at a bracket at the top,hard pipe to lower slave,hard pipe back to top slave,bleed nipple now on the top slave where the air wants to go.

ciderman · Mar 27, 2019

we were talking about that.
Is there risk of the pipe being damaged off road?

Chopz · Mar 27, 2019

Had a crappy brake after brake overhaul on my 88 but that was the britpart shoes
After a few hundred miles they bedded in the the brake pedal travel is now good

tottot · Mar 27, 2019

Keep the extra pipe tight to the back plate alongside the other and should be good. Adjust all brakes up before bleeding.

Tall Ratbag · Mar 27, 2019

tottot said:
Adjust all brakes up before bleeding.

It's actually better to do the opposite of this.

Although it sounds odd, the problem stopping the front brakes on 109s being bled is a pocket of air behind the extended pistons in the wheel cylinders.

If you adjust the brakes fully off, this pushes the pistons back in the wheel cylinders, and forces the air pocket out of the cylinders into the brake pipes - from where the air can be pushed out using either a brake bleeder, or even just the brake pedal. You should see a stream of bubbles released when you do this, While the air pockets are in the wheel cylinders, no amount of pumping or bleeding will shift them.

Obviously, you'll need to re-adjust the brakes afterwards to get a good pedal back!!

rob1miles · Mar 28, 2019

Agreed, I hate the job, but it goes OK. Loosen all the adusters to bottom the cylinders, easybleed, just crack the nipple, tight fitting bleed tube kept under the fluid level, bleed fluid level above nipple. If you are feeling keen take the nipple out and grease the threads so air can't get back up while you are bleeding. If the pedal is soft when the air is out its the master cylinder. Reason I sorted the bleeding was that my probelm was the master cylinder!

ciderman · Mar 28, 2019

Ahhh!

blue beasty · Mar 28, 2019

If I've had the drums off anyway I clamp the piston back in the slaves and bleed before reassembly.

I've also bled the top cylinder at the link pipe but you need lots of rags fer that

peter8315 · Apr 2, 2019

I agree with totott, you must have the bleed nipple at the top, so feed in down to the bottom and the return to top cylinder otherwise air gets trapped at top

rob1miles · Apr 2, 2019

Mine is as per std, bleed nipple at teh bottom on the TLS brakes, it bleeds OK with an easibleed, so long as the adjusters are backed off fully to cut the volume.

ciderman · Apr 8, 2019

Ok Thanks

Series 3 BLEEDING BLINKIN' 109 BRAKES

ciderman

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tottot

Well-Known Member

ciderman

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Chopz

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tottot

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Tall Ratbag

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rob1miles

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ciderman

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blue beasty

Leaks an prone to bits dropping off

peter8315

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rob1miles

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ciderman

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