Thread: Bleeding Brakes with vacuum bleeder.

A little O/T, but I recall the Military IIa's had many frustrations with their brakes, with bleeding being the main one. I don't know if all Mil spec IIas were the same, but many were fitted with two wheel cylinders on each front wheel, top and bottom. The brake line came into the top cylinder, and the bleed nipple was on the bottom! How anyone expected to be able to bleed something set up like that is beyond me. We had some success with pressure bleeders, but never perfect. At 2 Base Workshop we even got a bloke out from Girling, who suggested turning the backing plate upside down during the bleeding process. My suggestion that it would be easier to turn the whole car upside down was not well received.

I wonder if your vacuum bleeder would have worked.

Yep, the Deefer is a PITA to bleed 'conventionally', IMO actually impossible.

I think I've mentioned several times over the years I made a pressure bleeder from a Hills garden sprayer.
It was the only way I could get a pedal, and made bleeding a cinch by myself. Screw the cap to the M/C, pump up the spray tank, crack the bleed nipples and purge.

Glad you got it sorted.
Have to do the D2 when I get back to civilisation, it's a wee bit spongy and looong. The Nanocom will come in handy.

Originally Posted by strangy

Hi all, thought I would share my experience bleeding the brakes on the Defender.
Background - complete new system fitted (except hard lines) Braided flex lines. calipers, master cylinder, booster and rotors.
Quality items fitted.

I'm not new to bleeding brakes but the Defender has been the most troublesome I've come across to date.
I was expecting the bleeding to take longer than normal and had read and heard of frustrations with the system bleeding, but wasn't expecting it to be this tedious.
Bleeding with engine off was typical and gave a firm pedal - cycled around 1 and half reservoir of fluid.
When the engine started pedal went to the floor.
Bleed again with engine running finally gave a satisfactory pedal (about half a reservoir used) but after around 3 seconds the pedal would slowly sink to the floor.
After much more bleeding (3 reservoirs) and an unhappy assistant, I couldn't get a firm pedal to hold more than a few seconds before slowly sinking to the floor.
I decided the new master cylinder was a dud as the brakes were displaying classic internal MC failure behavior and I wasn't/couldn't get any air from the system.
Another new master cylinder fitted and same problem.
I couldn't have 2 dud MC so contemplated the inability to get a firm pedal.
My thoughts are the design in these dual piston calipers must have a hard time clearing air under what most would consider typical bleeding techniques and must be the problem. Some persistent aggressive bleeding was required.
Not having an assistant around caused me to lash out on a vacuum bleeder from Supercheap.

Using the bleeder is very easy, though has some behavior which needs to be understood.
The nature of a bleed nipple will cause air to be drawn in around the nipple thread whilst drawing fluid at the same time when under vacuum.
This makes it very hard to determine if the air seen in the tube is from the system or drawn externally.
This is where the vacuum gauge needs to be utilised for more than an initial hg value.
Watching the gauge pressure reduce, you can see the rate of vacuum reduction flicker/drop rapidly and then stabilise.
This is the indication of air being drawn from the system.
When the gauge consistently falls at a steady rate with no flickering the system should be free of air.
now..
I say "should" be free of air because the Defender was still playing shennanigans. The pedal was better but not good.
I applied nearly 3 times the vacuum suggested and cracked the nipple wide open and found this is what was needed to get the last air out.

Now I have a great pedal and added a very helpful tool to the kit.
Plus a new master cylinder now for sale.

The vacuum bleeder also comes with multiple adapters so you can test vac systems, valves, manifolds etc.

Some of you may already know this but hopefully it may help some others.

I also use a vacuum bleeder, but first remove the bleed nipple, wrap a few turns of thread tape around the thread and then replace it. I find this usually prevents air being drawn in around the threads when its cracked.

any pics of the Gizmo in action Strangy?

+1 for the vacuum bleeder.
I've got a Airboy bleeder I bought years ago while having issues bleeding the clutch on the County. As said earlier it sucks air around the bleed nipple so you can't go by clear fluid coming out, but I just run at least half a reservoir through for every corner and that's usually enough.
Also good for sucking out of the reservoir so there's less fluid when you disconnect something. Guess you could crack the nipple on the affected corner and suck the system dry, but I don't usually bother.
Mine doesn't have a gauge on it, so I just open the nipple a decent amount and let it rip. 10-15secs or so is generally all you can do in a burst without refilling the reservoir.

Makes bleeding so quick and easy that I no longer hesitate to disconnect a caliper or line for access, whereas previously I would have avoided it.

Steve

Originally Posted by strangy

Hi all, thought I would share my experience bleeding the brakes on the Defender.
Background - complete new system fitted (except hard lines) Braided flex lines. calipers, master cylinder, booster and rotors.
Quality items fitted.

I'm not new to bleeding brakes but the Defender has been the most troublesome I've come across to date.
I was expecting the bleeding to take longer than normal and had read and heard of frustrations with the system bleeding, but wasn't expecting it to be this tedious.
Bleeding with engine off was typical and gave a firm pedal - cycled around 1 and half reservoir of fluid.
When the engine started pedal went to the floor.
Bleed again with engine running finally gave a satisfactory pedal (about half a reservoir used) but after around 3 seconds the pedal would slowly sink to the floor.
After much more bleeding (3 reservoirs) and an unhappy assistant, I couldn't get a firm pedal to hold more than a few seconds before slowly sinking to the floor.
I decided the new master cylinder was a dud as the brakes were displaying classic internal MC failure behavior and I wasn't/couldn't get any air from the system.
Another new master cylinder fitted and same problem.
I couldn't have 2 dud MC so contemplated the inability to get a firm pedal.
My thoughts are the design in these dual piston calipers must have a hard time clearing air under what most would consider typical bleeding techniques and must be the problem. Some persistent aggressive bleeding was required.
Not having an assistant around caused me to lash out on a vacuum bleeder from Supercheap.

Using the bleeder is very easy, though has some behavior which needs to be understood.
The nature of a bleed nipple will cause air to be drawn in around the nipple thread whilst drawing fluid at the same time when under vacuum.
This makes it very hard to determine if the air seen in the tube is from the system or drawn externally.
This is where the vacuum gauge needs to be utilised for more than an initial hg value.
Watching the gauge pressure reduce, you can see the rate of vacuum reduction flicker/drop rapidly and then stabilise.
This is the indication of air being drawn from the system.
When the gauge consistently falls at a steady rate with no flickering the system should be free of air.
now..
I say "should" be free of air because the Defender was still playing shennanigans. The pedal was better but not good.
I applied nearly 3 times the vacuum suggested and cracked the nipple wide open and found this is what was needed to get the last air out.

Now I have a great pedal and added a very helpful tool to the kit.
Plus a new master cylinder now for sale.

The vacuum bleeder also comes with multiple adapters so you can test vac systems, valves, manifolds etc.

Some of you may already know this but hopefully it may help some others.

I bought the same bleeder the other day, they offer a life time no question asked warranty in their trade catalogue, Now I have no excuse to do some brake fluid renewals.

Originally Posted by Pedro_The_Swift

any pics of the Gizmo in action Strangy?

Sorry Pedro.
I might do a vid if/when I use it again.
In this instance pic/video of the owner and assistant would be more entertaining than the gizmo.

I find the pressure bleeder much more simple to operate.

I have one of these, it is a bit expensive (and im sure could be done much cheaper/easier if you made your own).

Product List :: Specialty Tools, Workshop & Lighting :: Brake & Clutch :: Pressure Brake Bleeder Kits :: BRAKE & CLUTCH PRESSURE BLEEDING KIT - SP Tools Australia

You can fill the pressure bleeder itself with brake fluid (well mostly fill) and that way you don't need to worry about the master cylinder running dry.

Also its much more obvious when air is coming out than the vacuum ones.

I used to have to bleed the brakes on my track car every month for the track day so tried quite a few different ways (kits with one way valves/bottles, vacuum bleeder, slow gravity bleeding, dodgy home made pressure) and found this the easiest.