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Bleeding Brakes

mojobaby

mojobaby

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For the past 2 days, I've been trying to bleed my brakes but haven't had any success.

I have drum brakes, both front and rear. I've replaced all the brake shoes, new brake cylinders on all wheels and also a new master cylinder.

I also blew out each brake line to clear any 20 year old blockages.

Working by myself, I used the tube and bottle method.

Starting with the furthest away wheel, I managed to pump brake fluid until it came out of the bleed nipples on all the wheels.

My brake pedal had no resistance at all and went all the way to the floor.

I took the front left drum off and could see some movement in the brake shoes.

I did the same to the back left wheel and there was no movement at all, so I took off the brake shoes and tried again and the pressure blew out the one side of the brake cylinder.

I put everything together again and bled the system again and still I have no resistance in the pedal. It goes straight to the floor.

So what am I doing wrong. Can there still be some air in the system?

Help please!!
 
hi - it is air.

Unfortunately, the master cylinder often needs bleeding 'on the bench' (if it doesn't have it's own bleed nipple on the top) before fitting to the car as otherwise the air trapped in nooks and crannies is almost impossible to extract. This does require blanking off spare outlets from the master cylinder (if there are any), and pumping the cylinder by hand with it in a vice - use a rod or blunt screwdriver to push the cylinder steadily in, obviously with fluid in the reservoir above it. A pipe or hose from the outlet is needed, the end submerged in brake fluid to prevent air being sucked back along the line. If there are two outlets, then one should be blanked before the other is bled as above. I have used a brake pipe-end nut with a crimped-over short pipe attached to blank an outlet; a bleed-nipple may also fit. Preferably keep the outlets blanked until fitting to the car - a mess is sure to ensue but it does work.

Otherwise, invest in a pressurised bleed system - I have a pump-up plastic canister with an end cap that fits most European (including R4) master cylinder reservoir tops. It's a Sealey vs820 - see ebay - and not all that cheap but I have used it a lot and despite it's imperfections it is very effective, even at a low-ish 10 psi (but better at 15). Pour in about a litre of brake fluid into the bottom to enure air doesn't pump out of the thing, and make sure there is always plenty of fluid in there while you are bleeding (re-bottle the spare fluid afterwards, but be aware that the fluid slowly absorbs water - corroded pistons and spongy pedal if left out in the air for ages and re-used).

Once again I researched this bleeder in OCD-fashion before purchasing, and settled on this as the best DIY option for me.

Any pressurised bleed is much better than the foot-pedalling method for all bleeding really, as the master cylinder does not get over-exerted in the bleeding. During pedal-pounding, sometimes the pistons inside the master cylinder reach parts that only Heiniken can, leading to premature seal failure during the bleeding of used master cylinders. (Painful experience of rapid clutch & brake master losses soon after bleeding on other cars!)

Guinness-driven by an insomniac at 2am :)
 
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Thanks Adam for that "middle of the night" response.

That all sounds quite involved. I had a suspicion that there might be air somewhere, but I thought it might be trapped in the brake lines somewhere. Never thought about the master cylinder as the last one I put into my GTL worked immediately.

Now I just have to find something to blank off the outlets.

Here are 2 photos of the master cylinder that was in the car. I thought that it was faulty and thats why I bought a new one, which I now think was probably not necessary.

In the first photo the 2nd from the left appears to be a spare outlet, but both 1 and 2 lead to the back brake regulator valve.
IMGP1533.jpg
Same master cylinder, just cleaned up a bit. Can you tell me what the nipple is used for. Is that perhaps for bleeding the master cylinder?

IMGP1534.jpg
 
It looks a lot like a bleed nipple for the master cylinder, but isn't that at the bottom when it's in the engine bay? If so, it must be only a drain. Any blanks screwed in need to be air-tight, else working the piston will suck air into areas just bled (yes I did do that!).

Maybe it'll bleed itself OK next time without all the rigamarole (ever bleeding hopefull).....
 
bit early for your reply Adam, I wasn't expecting it until at least 3am:)

Yes the nipple is towards the bottom, probably in the 4 o'clock position.

So I'm going to have to look for some blanks for the outlets,

Thanks for all the advice and I'll let you know my progress
 
This bleed nipple is to bleed the pressure drop indicator circuit (a separate small piston). Without doing this you will never get rid of all the air. You have to first bleed the four wheels just like you did, then bleed this circuit, then possibly go over the system once again, but always ending with this nipple.
There is no point "bench bleeding" the master cylinder, as air will enter the lines again when putting the master cylinder back on the car. Plus, with a full master cylinder and fluid leaking all over the place, it will be a hassle to connect back all four brake lines.
If you don't have an assistant pressure or even better vacuum bleeding works great when you have to fill the whole system from dry.
 
Thanks Angel, did as you suggested and a lot of air came out of that bleed nipple. But still I have no pressure:(

I think it probably needs a couple of more times. Going to see if I can find a vacuum pump tomorrow, hopefully that will be more effective.
 
I still haven't decided whether to get a vacuum pump or a pressure pump:dontknow: I've given up trying to bleed the brakes with the brake pedal as it just doesn't work for me. I've bled my brakes quite a few times before but never when the brakes lines and master cylinder were empty to start with.

In the meantime I've improvised and made my own vacuum system and it works okay, with only one small problem. And that is when I unscrew the bleed nipple to vacuum, it also draws in air from around the sides of the nipple.

I've tried blocking off the nipple threads with grease but that only works for a while and then air gets back in.

If I buy a proper vacuum pump is that problem going to continue? Perhaps a pressure system would be better like Adam's Sealey vs820?

so vacuum or pressure, that is the question
 
I have been using a vacuum bleeder for some years and it beats the pressure bleeder that I had been using (eezibleed) everywhere. I coat the threads of each nipple with PTFE tape before commencing bleeding. It works wonders, no vacuum leak from the threads.
Mojo, try to find an assistant and bleed the following way: tell him/her to pump the pedal three or four times then hold it depressed. Then open the nipple just for a second, close it, then tell the assistant to release the pedal. Do this 2-3 times at each wheel,starting with the front ones, then the rear ones, then the master cylinder nipple.
 
I've been using the single person bleeding method and thats probably when air re-entered the system through the bleed nipple, a vacuum leak from the threads every time the brake pedal returns to its upwards position, as you say.

Today was a lot more successful. I followed your method with my wife pumping the brake pedal. At least now there's a lot more resistance in the pedal. I'll do the same again tomorrow. It worked perfectly:)

And excellent advice re the PTFE tape, I'll be sure to remember that for the next time, when I get a vacuum bleeder.

So thank you Angel for returning my sanity, I was starting to doubt myself.

And thank you Adam for all your help and advice, much appreciated:)
 
PTFE tape is unnecessary on the threads. The nipples seal on the tapered seat not via the thread. Brakes leave the factory with no tape. Back to the original issue, I always bleed with my wife on the pedal and me underneath. I have also experienced (but not on an R4) that air will rise to the top if the car is left standing and a harder pedal can appear a day after.
 
I am happier using a pressurising bleed system - that way (probably) the air emerging from the nipple is from inside the hydraulic system and not being sucked into the bleed pipe through the loosened threads of the nipple from outside, as could happen with a vacuum system. That would be a false stream of bubbles.

A good flow of fluid through the bleed nipples should not leave air in the pipes; I can't imagine relying on gravity to finally bleed the system overnight.
 
I advised coating the bleed nipples with PTFE tape in case bleeding is done with a vacuum pump. A loosened thread will leak more air in the bleeding device than pull brake fluid. It has nothing to do with a tightened bleed screw havingto hold 80 bars+ of hydraulic pressure...
 
OK Angel I understand your PTFE use now. I've never used it as when my wife is pressurising the system with the pedal, I am down below opening the nipple and tighten it again before she lifts off so no air can get in. I then repeat until all air out. Usually this works everytime but last year on a Cortina it did not. I was told my a mechanic to get a better pedal by adjusting the rod behind the servo. This worked and the day after the brakes seized on as the air had risen and left the system. I had to readjust the rod back to original position and all was OK.
 
Have just read these replies after resorting to the forum after tearing clumps of hair out and banging head on the garage floor
I have just replaced all brake lines + rear cylinders + calliper seals and cylinders + master cylinder (3hole type) then bled the
system the normal two person method then trying opening each nipple till running clear then with a pressure gun then with
a vacuum tool using each about 3-4 times finally running out of fluid about 5 litre I even tried blanking of the rear then the
front in turn still no pedal so will now try this as a last resort
 
Sometimes the master cylinder can trap air if it's not filled & bled 'on the bench' - ie not on the car. I've needed to do this once - I made up some short brake pipes and crimped/soldered the ends shut then bled one master cylinder exit at a time, leaving the others blanked. piston was pumped using a rod/screwdriver, master cylinder held in a vice. Can be messy, but is effective. Keep the exits blanked off for as long as possible until car brake pipes are reconnected.
 
Why would it matter if the cylinder was on the car or bench if using the above method? Does the pedal not depress as far as a blunt object would on a bench? I have drums all round and replaced master. Have tried usual methods and pressure and have bled master on car and have zero pedal unless i clamp off some hoses. i was using bleed nipples and clear hosing on the master perhaps and was closing when pedal down etc but still no luck. seem to be getting fluid through at the rear more than fronts. I even lowered vehicle down on to axle stands at rear in case the valve was an issue with rear end hanging but no difference. The original cylinder had one way valves that screwed off for the outlets to the front but this new one is just one piece. Highly frustrating. Ideas?
 
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