Bleedin' Brakes!

[adam quantrill]

Well as the weather was nice I decided to have another go at the spongy brakes.

I did find a stuck piston at the rear which I freed up, and put a ittle copaslip on to prevent it happening again.

But this still didn't explain the sponginess. So I tried bleeding from the front driver's side using the Harry Quantrill method (child in the driver's seat pumping the brake pedal).

However it just seemed to be coming out like champagne. I stuck 1.3l of fresh fluid through it, and at the end it seemed a little firmer, but there were still bubbles coming out.

I'm wondering how the air is getting in there, and the only thing I can think of is that the master cylinder is somehow admitting air into the bore - possibly where the plunger goes in and out?

Anyone else seen this sort of problem, or have any other suggestions?

Luckily I have a spare master so I might try swapping it over tomorrow (let's hope it's a serviceable one!)

Edited by adam quantrill on Saturday 9th February 17:56

[rev-erend]

As you say - there must be a leak somewhere.. time to peel back some of the rubber and check for seepage.

[adam quantrill]

I did pop the master cylinder off but there wasn't a load of brake fluid (or any other seepage) in the servo unit.

I expect changing them over would only take a half hour so I'll try it - what the hell.

[dickymint]

I could never sort out my brakes by bleeding from the front. So I bought one of them eezybleed kits and one of Shpubs flexi extension tube kits - then bled from the rear caliper and job done. I would guess also that an eezybleed (pressurised with the spare tyre) would show any leakage?

Edited by dickymint on Saturday 9th February 22:05

[adam quantrill]

I expect you got a decent flow of bubble-free fluid through, though Richard?

My problem seem to be that something is introducing air bubbles, given that there don't appear to be any leaks on the pressurised side of the system, the master cylinder does seem to be the main suspect.

I certainly don't want to start bleeding from the rear until I get a good run of bubble-free from the nearest front caliper, or else there'll be air eveywhere!

[djc1001]

Hi,
Noddy question - but are you sure the pumper is holding the pedal down while you close the nipple on each pump, or the system just sucks air back in on the padal up stroke - otherwise you can spend all day and get nowhere.
As above - the pressurised systems work great and make it a one man job, you do need to do all three (only one at the back) to get all system air out.

r's
david

Edited by djc1001 on Sunday 10th February 09:34

[350zwelgje]

As mentioned before, making sure bleeding nipple is closed under correct circumstances, but you know that one. Other source I had were soggy seals holding the reservoir. Seems that even when they are not leaking that air can be sucked in. And after replacing my brake master cylinder noticed that the 3rd connection was not closed off properly. Based on this I have no problems bleeding the breaks of the wedge.

Rob

[adam quantrill]

Well it was the master cylinder in the end, sticking air into the system. The replacement bled clear fluid after only 3 or so pumps.

I then bled the other front, but it was still quite spongey.

An 11mm hex socket fitted the rear bleed nipple perfectly - and snapped it off to boot! So I used the "Leigh" method on the rears and undid the connector pipe from the caliper that has the rear bleed nipple.

After some pumping I got the cruddy fluid out, and what appeared to be a few air bubbles (the pumping gets a lot harder presumably 'cos of the bias valve).

I then clamped the pistons back in on that caliper to expel any bubbles there, put the pipe back in, pumped one last time while tighening the pipe up.

Result! Brakes are now nice and firm, no annoying slack or sponginess. Bring on the MOT!

[TVRleigh_BBWR]

It's also worth doing all the nipples on the fronts, some have about 3. when I did mine with a garrage pressure system, we got bubbles out of all the nipples. even tho we did the top ones 1st.

[GV]

Well I tried bleeding the brakes today without much success using the EZ Bleed. I pressurized the system and cured a couple of leaks. Started off on the n/s then the o/s and finally the rear. Got clear fluid and no bubbles at all bleed points but the pedal is still quite spongy especially when the car is started - but not when pressurized when the engine is off. I ran out of fluid so I stopped until I get some more.

I'm going to get an assist next time round to pump the pedal whilst under pressure to see if it will sort out the problem otherwise I'm stuck....any ideas?

[TVRleigh_BBWR]

The pressure systems work better than any pedal method.

As said you may want to check all nipples and pipes make sure you not got a bit of air stuck somwhere.

[matt-man]

I changed the master cylinder this winter as the old one was pooped.

Changed the fluid totally and i could not get the brakes to loose spongeness, blled after bleed afer bleed. In the end, the only way i could get it to go was have dad pumping the pedal and on every push open and close the bleed nipple.

Worked perfecty this way and got rid of any problems!

Wish i'd though of that before i bled the system 4 times!!!

[GV]

matt-man said:

I changed the master cylinder this winter as the old one was pooped.

Changed the fluid totally and i could not get the brakes to loose spongeness, blled after bleed afer bleed. In the end, the only way i could get it to go was have dad pumping the pedal and on every push open and close the bleed nipple.

Worked perfecty this way and got rid of any problems!

Wish i'd though of that before i bled the system 4 times!!!

I think Matt's right. I was reading a thread on a kit car build and the guy also used the pumping method...I'll try that next. By the way, which car is the master cylinder from??

Edited by GV on Monday 7th April 19:45

[350zwelgje]

Many (dear I say most?) are cortina, but getting hold of one or an overhaul kit can be daunting.
There is another tread with information where someone sourced an overhaul kit. In the post you can find where he ordered and what the partnumber was (or how to order).

Rob

[leorest]

GV said:

matt-man said:

In the end, the only way i could get it to go was have dad pumping the pedal and on every push open and close the bleed nipple.

I think Matt's right. I was reading a thread on a kit car build and the guy also used the pumping method...I'll try that next.

Another method if ALL else fails is to repeatedly and quickly pump the pedal half a dozen times with the nipple closed and then with the pedal held down open the nipple and let a shot of aerated fluid out, close nipple, while there is still forward flow, and repeat until satisfied. Usual H&S advisories apply e.g. if you need advisories then you should be letting a professional do the job.

[shpub]

I found the princess callipers were next to impossible to bleed correctly which was another reason why they were replaced with Wilwoods many years ago... that and the difficulty of getting repair kits. To get mine to bleed correctly I had to have someone pump the brake pedal with an easibleed forcing fluid through followed by removing the calliper, putting a piece of wood in the gap where the disc would be and then inverting the calliper and repeating the operation. It seems that air can get trapped internally and this causes the problems.

[GV]

shpub said:

I found the princess callipers were next to impossible to bleed correctly which was another reason why they were replaced with Wilwoods many years ago... that and the difficulty of getting repair kits. To get mine to bleed correctly I had to have someone pump the brake pedal with an easibleed forcing fluid through followed by removing the calliper, putting a piece of wood in the gap where the disc would be and then inverting the calliper and repeating the operation. It seems that air can get trapped internally and this causes the problems.

How mutch are Wilwoods?

[Dave Meredith]

GV

I'm exactly where you are at the moment so it will be interesting to see if we can solve this problem.

My 350 passed the MOT a few weeks ago which always surprises me because I think the brakes are really poor.
It slows down rather than brakes and it would be impossible for me to leave skid marks on the road under braking. Good for tyre wear I suppose!

I've replaced the seals and bled the brakes. Still no good. I've bled the brakes using an EZ bleed kit but still no good. I going to bleed them using the 'pumping' method -open nipple on downstroke and close on upstroke.This should stop any air being sucked into the system at the nipple end. I'm not very confident though because the EZ bleed method should not draw air back into the system and this hasn't worked either

Next step might be replacing the master cylinder or getting a garage to bleed them

[TVRleigh_BBWR]

You may want to up the presure so it's on it's limit. I know the pro systems the garages use run at a higher pressure.

Also as said before bleed all 3 nipples as air can get trapped all over the place.

or do as steve said take them off and rotate them.

[Dave Meredith]

Leigh

The EZ bleed kit instructions say 20 psi tyre pressure but this was hardly enough to push the fluid out of the nipples so I used another tyre with 32psi in it.

I've got the original Granada calipers.I thought rotating the caliper only solved a Princess 4 pot problem ie trapped air. In any case how can I rotate the caliper without removing it and letting air in

Interesting that you say garages use higher pressure on their bleeding equipment. I might cut my losses and get them to do it.