Bleeding brakes from bottom up

[danny_galaga]

 

Some of you guys bleed your brakes from the bottom up with some sort of pump. You've sold me on the idea. So now I need to know exactly what you are using. Specifically. Not a general comment, but specifics. If it's a popular thing to do there must be tools for it.

 

So tell me you got a Maxx 2000 Brake Wonder from Supercheap or whatever that I can put oil in and hook it up to the bleed nipple, job done. Don't tell me you found some old oil can of a special type that hasn't been made in 50 years, and then modified it 'just so' with home made machined parts etc.

 

I just need to get cracking 🙂

[rodgerc]

Here’s the one I used for the 3-1/2 minutes it takes to complete the job on Matco brakes. You’re welcome to borrow it to save $20

[tillmanr]

I have a similar style from supercheap but use clear tube to connect to the bleed screw just to monitor the fluid. 

[skippydiesel]

I use disposable syringes (purchase from chemist or animal feed merchants) & clear hose to suit (Bunnings) - low cost & can, with care (flush with metho or Iso, lube plunger with silicon)  be reused several times. The amount of brake fluid is very small, so a 100 mm (or smaller) syringe will usually do the job.

 

Don't get hung up on bleeding from the bottom - you may find that you bleed from wherever, to get that last bit of air out of the system.

 

If possible never drain your brake system ie when replacing fluid, use fresh unused fluid to flush the system, avoiding air entry.

[Thruster88]

Be sure to use the correct type of fluid for your system. May be car type brake fluid or aircraft type hydraulic oil.

[onetrack]

Google "vacuum brake bleeder" and make your selection from a wide range of choices. They're nearly all Chinese, anyway, so no need to pay $139.99 for Supercheaps ripoff - buy a $20 one off eBay, they come complete with hand vacuum pump and vacuum gauge and case.

[skippydiesel]

24 minutes ago, onetrack said:

Google "vacuum brake bleeder" and make your selection from a wide range of choices. They're nearly all Chinese, anyway, so no need to pay $139.99 for Supercheaps ripoff - buy a $20 one off eBay, they come complete with hand vacuum pump and vacuum gauge and case.

Good system BUT again don't get hung up on just one way of doing it.

 

Aeroplanes are not like automotive systems (easy as) they are finitiky buggers that may need more than one technique to get to that airless happy place😁

[facthunter]

Automotive with Brake antiskid systems can be a bitch. If you bleed downwards you have to go fast enough to take the bubbles with you. Ordinary brake fluid is hygroscopic and the system should be replaced by new oil  regularly say 12 months just to reduce corrosion.  Nev

[IBob]

I used a small cheap greenhouse pump sprayer with neoprene tube attached, but most of them leak at the screwon top, so test if buying.

 

However, I like the idea of the pump oilcan above much better: the pumped up sprayer delivers the fluid at an uncertain rate, and needs to be shut off real quick at the end of the fill.
 

[RFguy]

I'm told that a good way is to attach the output of the caliper nipple to a long length of silicone tubing, take it all the way up and (back)  into the master cylinder resv. (be sure resv is full). and just pump using pedal/park brake ) around the system around and around until all the air gets pumped out, bubbles going into the resv of course just bubble off. I keep writing resv because the word reserviour etc the spelling has forever elluded me.

[skippydiesel]

5 hours ago, facthunter said:

Automotive with Brake antiskid systems can be a bitch. If you bleed downwards you have to go fast enough to take the bubbles with you. Ordinary brake fluid is hygroscopic and the system should be replaced by new oil  regularly say 12 months just to reduce corrosion.  Nev

Never had what I would call  problem Nev (I do my brake fluid every 2 years or KM's, whichever comes first). With the aid of a well trained family member, on the brake pedal and topping up the reservoir , ( I do the sometimes messy/dirty job underneath) it all seems to work out very well. it would seem most if not all cars of the 2000's have ABS - so far no probs.

[skippydiesel]

2 minutes ago, RFguy said:

I'm told that a good way is to attach the output of the caliper nipple to a long length of silicone tubing, take it all the way up and (back)  into the master cylinder resv. (be sure resv is full). and just pump using pedal/park brake ) around the system around and around until all the air gets pumped out, bubbles going into the resv of course just bubble off. I keep writing resv because the word reserviour etc the spelling has forever elluded me.

Maaaate! The trick is not to get air in the system in the first place.

[danny_galaga]

1 hour ago, skippydiesel said:

Maaaate! The trick is not to get air in the system in the first place.

No, I get it. If you keep pumping and it's going straight back to the reservoir, any bubbles are going to be at the top of the oil in the reservoir. So they don't get drawn back in. Nice simple idea. Only problem is one of the reasons I'm sold on'bottom up' is that it's ridiculously fiddly to open the lid of my reservoir. Hence I may as well go bottom up and maybe avoid opening the lid 

 

System is matco using mineral oil by the way.

 

Edited November 8, 2023 by danny_galaga

[RFguy]

yeah it just goes around the loop..... I had a problem where I had air occassionally getting into the system around a seal.... so its a quick bleed.. when done, tighten nipple, and holding pitched tube high , let go  let rest run back into the resv or bottle. anyway, you get the idea.

 

but but when you use bottom up, you have to watch you dont overflow it.... so the lid is involved?.

on mountain bikes, we used to just open the recv up, and pump the brakes while tapping the lines with a back end of a screwdriver, that brought bubbles up

the round the loop method I first learned on mountainbikes...

Edited November 8, 2023 by RFguy

[Blueadventures]

I do brakes the old car way a short (200mm) hose into a small baby food glass jar. Small amount of fluid in it so end always submerged. Depress brake, open nipple then flow and close and then repeat. Works well.

[skippydiesel]

1 hour ago, danny_galaga said:

.........................

 

System is matco using mineral oil by the way.

 

Only done the brakes on three aircraft (several times) - despite two being the same "model" the brakes were slightly diffrent, requiring a flexible approach to bleeding. I think that's part of the problem, no two systems are exactly the same.

 

I doubt the type of hydraulic fluid makes much difference to "bleeding".

 

I don't think there is much if any functional benefit in using aviation fluid V automotive, other than cost & ease of acquisition of automotive. NOTE:  Check and double check you are using a fluid compatible with your system - the wrong fluid is likely to damage seals/buckets and leave you with no brakes and much expense.

 

I do think the systems, on RAA class aircraft, can be difficult due to using very small ID pipes, lowish pressures/flow (particularly for hand actuated systems), odd pipe routing (sometimes  a U bend or a master cylinder, traps air, makes life difficult), duel masters, small capacity reservoir or no reservoir, etc etc

 

In my limited experience, a combination of techniques (including much bad language)seems to deliver a non aerated fluid. Once you get to that happy place, every effort should be made to avoid future air entry. 

[Blueadventures]

16 minutes ago, skippydiesel said:

Only done the brakes on three aircraft (several times) - despite two being the same "model" the brakes were slightly diffrent, requiring a flexible approach to bleeding. I think that's part of the problem, no two systems are exactly the same.

 

I doubt the type of hydraulic fluid makes much difference to "bleeding".

 

I don't think there is much if any functional benefit in using aviation fluid V automotive, other than cost & ease of acquisition of automotive. NOTE:  Check and double check you are using a fluid compatible with your system - the wrong fluid is likely to damage seals/buckets and leave you with no brakes and much expense.

 

I do think the systems, on RAA class aircraft, can be difficult due to using very small ID pipes, lowish pressures/flow (particularly for hand actuated systems), odd pipe routing (sometimes  a U bend or a master cylinder, traps air, makes life difficult), duel masters, small capacity reservoir or no reservoir, etc etc

 

In my limited experience, a combination of techniques (including much bad language)seems to deliver a non aerated fluid. Once you get to that happy place, every effort should be made to avoid future air entry. 

Also worth looking at the level of calliper as if bleeder is not highest point air will be trapped at top; so need to remove remove calliper and turn to have bleeder at highest point insert a spacer if cannot place over disk while continuing to bleed.  Need to do this at first on the Skyranger original brakes.

Edited November 8, 2023 by Blueadventures

[skippydiesel]

20 minutes ago, Blueadventures said:

I do brakes the old car way a short (200mm) hose into a small baby food glass jar. Small amount of fluid in it so end always submerged. Depress brake, open nipple then flow and close and then repeat. Works well.

I assume you have an assistant "depressing brake". I have trained mine to loudly intone DOOOOOOOOWN (slow depression)- UP.

I find a ring spanner to be the best for working the nipple. The bleed hose goes on after "cracking" the nipple, while spanner remains in place.

OPEN bleed niple slightly after the down commences.

CLOSE nipply just befor end of down.

Repeat, until no sign of old fluid or air.

I usually start with the slave/wheel  cylinder closest to the reservoir - carefully drain as much old fluid as you can, avoiding sucking air, before adding fresh fluid to the top of reservoir. Your assistant is in charge of replenishing reservoir as needed.

In a vehicle - avoid depressing brake pedal all the way to floor (if in doubt small wooden block placed under peddle) prevents possible overextension/damage to piston rubbers.

Opening nipple slightly after assistant commences down stroke, ensures a good high pressure scouring (removal of any contaminants including air) of system.

Closing nipple, while under pressure, reduces chance of air entry, as does Blues partially filled baby food glass jar (I use a peanut butter plastic one).

 

In an aircraft I use both bottom up, and bleed down (very similar to vehicle technique). I have tried vacuum bleeding with some success.

 

Sometimes removing air bubbles just requires a sufficiently fast flow of fluid, to force the air to exit with the fluid - do whatever it takes.

 

[Blueadventures]

1 hour ago, skippydiesel said:

I assume you have an assistant "depressing brake". I have trained mine to loudly intone DOOOOOOOOWN (slow depression)- UP.

I find a ring spanner to be the best for working the nipple. The bleed hose goes on after "cracking" the nipple, while spanner remains in place.

OPEN bleed niple slightly after the down commences.

CLOSE nipply just befor end of down.

Repeat, until no sign of old fluid or air.

I usually start with the slave/wheel  cylinder closest to the reservoir - carefully drain as much old fluid as you can, avoiding sucking air, before adding fresh fluid to the top of reservoir. Your assistant is in charge of replenishing reservoir as needed.

In a vehicle - avoid depressing brake pedal all the way to floor (if in doubt small wooden block placed under peddle) prevents possible overextension/damage to piston rubbers.

Opening nipple slightly after assistant commences down stroke, ensures a good high pressure scouring (removal of any contaminants including air) of system.

Closing nipple, while under pressure, reduces chance of air entry, as does Blues partially filled baby food glass jar (I use a peanut butter plastic one).

 

In an aircraft I use both bottom up, and bleed down (very similar to vehicle technique). I have tried vacuum bleeding with some success.

 

Sometimes removing air bubbles just requires a sufficiently fast flow of fluid, to force the air to exit with the fluid - do whatever it takes.

 

Do solo; easy on mine as single lever hand brake on stick and can reach both the lever and spanner on caliper nipple.

[danny_galaga]

I've bled a few car brakes in my time, much like bluesadventures method. It's what dad taught me. 

 

I only mentioned it's mineral oil because someone started to go on a tangent about it so I thought I'd nip that in the bud. I fully understand the method should be much the same 🙂

 I think I'll try the vacuum brake bleeder, else syringe and tube. Imma let that oil just overflow in the reservoir but wrap a rag around it first. Such a stupid design ..

 

[RFguy]

Skip, the whole "OPEN bleed niple slightly after the down commences, CLOSE nipply just before end of down."

- you dont need to do this !

 

Just tube it out to a bottle (which of course has end always in fluid) and just pump the first pedal in the system until no more air is present in the 40cm  of tube between the caliper and the bottle, lock the nipple off and it is DONE ! No need to

check anything....

then pour what's in the bottle back into the resv if you want to reuse it ( or top up the resv weith new fluid ) etc

the Piper has 5 cylinders... (park, 4 pedals) .

[skippydiesel]

RF -

 

After much experience/experimentation,  I have found that pressurising the system, to bleed & stop, prevents any air from entering (the nipple once cracked/open is not an airtight valve) AND  in addition may have a  scouring (cleaning out) effect due to the sudden rush of exiting fluid.

 

No offence but your idea, while good in theory, does not accomodate any imperfections (air/fluid leaks) in the system. The imperfections may be due to nipple  manufacturing tolerances, dirt, wear or seal deterioration.

 

The problem with nipple integrity, can also cause the vacuum bleeding system to be ineffective.

 

As to returning fluid to the reservoir - never having had spontaniouse air in a functioning brake system, I am always bleeding to replace old fluid or air bleed after a brake repair. In either case I would not return potentially contaminated fluid to the reservoir.

 

What is the significance of "the Piper has 5 cylinders... (park, 4 pedals) "?

[pmccarthy]

I agree with Skippy. Once cracked, the valve lets air in along the thread so you need to do the open/shut business. Or so I have found.

[danny_galaga]

Just ordered a vacuum brake bleeder on eBay. 

[danny_galaga]

I realised after I ordered it that this device probably entails adding oil into the reservoir 😄. But it's only 23 bucks. Considering how much I've blown on a project I'm not even interested in anymore, it's chump change!

So in the end maybe the syringe and hose will do what I want. I'm in Noumea right now. Maybe next week. If I fix the brakes I can taxi it. Might help make me excited about it