Manky's Pop.

[Manky Monkey]

Right, many thanks to my buddy Mr Baychimp for giving up his evening to help me tackle the brakes again.
Back to basics with him in charge of pumping the brake pedal & pouring brake fluid all over the cab floor, topping up the reservoir, while I opened & closed the bleed nipples.
Still not quite there, but a definite improvement. Using the pressure bleeder last night, I was getting a stream of about a dozen large bubbles from each nipple each time. That's down to one large "burp" on the first opening now & nothing on subsequent goes, until I came back to that corner of the car again when it'd be back to one bubble again. Same at the remote servo under the dashboard.
One new development though- the 2 rear drum brake nipples started producing a stream of tiny frothy bubbles if the bleed nipple was left open longer than usual. Within those were small white/silver flecks. it's only happening on the rear brakes. Can't make out what they are but I'm wondering if it's dissolved PTFE tape? Does it dissolve in brake fluid? The rear brake line passes through a residual valve, a one way valve & a short length of Goodrich type flexible hose, (to allow for rear suspension travel), then goes to each rear drum via a brass T piece. No obvious leaks in any joints.
We eventually started running out of daylight & fluid at about 9.0.clock so called it a night. The pedal travels maybe 1 1/2" before "biting" & pumps up a little on subsequent pushes, but not a huge amount.
I'll buy yet more fluid tomorrow afternoon & ask Mr Loon to give me a hand ...foot, to do it again. Yes, the fluid in the bleed bottle was filthy, but I've been tipping half of it away as it filled & we've gone through 2 litres of fresh fluid so far. Tomorrow I'll tip all the old fluid out of the bottle & start with fresh clean stuff, which might show what's going on better.
Any opinions, other than keep plugging away at it?

[Manky Monkey]

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[Olds]

 Frothing sounds like cavitation bubbles ( caused by forcing fluid through a restriction ) Try not pressing so hard on the pedal while bleeding. Too high a pressure on a pressure bleeder can cause the same effect.
That fluid looks worse than the other day.
 One thought on  the flecks. If you have ever wrapped the bleed nipple threads with ptfe tape, say to use a vacuum bleeder, then the repeated opening and closing, may be causing it to break up.

[poprodder]

andy, good luck with the brakes, but maybe next winter is there anyway they can be redesigned to make operation and bleeding easier? i know your resticted by space, but this must realy piss you off having problems every single time.

[kapri]

We were restricted by time the last time around as we HAD to make what was there work to get it through SVA . There are better and simpler systems to use and I'd consider doing that LATER !!

[kapri]

I agree with Dave re cavitation bubbles , it's the big burps that are ehe problem. Meanwhile 1.5" sounds fine. Are you trying to make it bite right at the top as that's NEVER going to happen. Measure the actual travel at the m/c pushrod , you should be seeing around 10-12mm max. Multiply that movement by pedal ratio and it'll tell you what to expect at  the pedal pad.

[Manky Monkey]

O.K, I'll check the pushrod travel next, (might have to go & collect some powder-coating this afternoon).
Yeah, Bob, (BayChimp), was stomping pretty hard on the pedal -he's complaining of a worn out foot this morning Not had the tiny bubbles before so that might explain it.
Already chatted to Mr Olds about fitting remote bleed nipples for the servo at some point.
Fresh fluid & a clean start & go from there. 

[Tony oily bike]

Agree with the guys with respect to operating the brake pedal fairly slowly. Agree with the idea the white flecks could be bits of PTFE tape broken off by repeated undoing/doing up of the brake nipples (PTFE is about as inert as you're gonna get so dissolving isn't going to be an issue. 'Teflon' is DuPont's trade name for PTFE, as in non-stick frying pans etc).

Sometimes on the bikes, the brake lever is pulled back to the bars and locked in position (big elastic band type thing) overnight to allow air to rise to the highest part (the lever and reservoir). Don't know if this could be applicable to your situation, but maybe worth considering.

Another idea worth thinking about is closing the bleed nipple just before the brake lever reaches the end of its travel, this way basically eliminates any poss of suck back from the bleed nipple, and the brake pedal operator can then feel the firmness of the pedal at the end of travel, then compare it when the pedal is released and re-applied (just in case there's any air sucked in from 'elsewhere').

Don't cha just love bleedin' brakes! 

[Mendalot]

It's interesting reading the above posts on this subject, over the years I have applied just about every different way there is to bleed brakes including having purchased several types of pressurised bleeding systems. But if I ever got a problem set of brakes, I always reverted to my trusted solo bleed pipe, which cost about £4.00!!, And using gentle steady pumps on the pedal to push the fluid through the system and out of the non return valve, always seems to work. They are still available on ebay.   Hope you get it sorted soon Andy.

[Olds]

My Ducati had  non return valves built into the bleed nipples. Wonder if they are available in imperial sizes ?

Yep, Goodridge do them.  About £11 each though.

[phunkie hiboy]

Meanwhile 1.5" sounds fine.

Don't forget this is without it running. Soon as you start it up and the servo comes into play the pedal will drop further.

[Manky Monkey]

We were discussing that last night -general consensus was that the pedal would lift with the servo running, but I wasn't sure & checked it in my Fiesta when I left -it definitely drops.
No chance to try again this afternoon -I had to go & collect some powder-coating & leatherwork for my motorcycle project, plus we had torrential rain here all day, but fresh brake fluid bought. I'll give it another go over the weekend.

[the coppersmith]

I'd be concerned with the black fluid, thats contamination by something breaking down, rear seals or master seals. If you are still getting bubbles may pay to look at rear cylinders, see if you have any mess.

[terry t]

I'd be concerned with the black fluid, thats contamination by something breaking down, rear seals or master seals. If you are still getting bubbles may pay to look at rear cylinders, see if you have any mess.

I was thinking that? I would check the vacuum unit 1st, if air on all brake cylinders

[Manky Monkey]

Took the afternoon off from the workshop today. Still have to do a full day's shift at the Post Office on Saturdays so had worked 8 hours, but felt lousy & just needed a break from the Pop. So I went to a steam rally in Wiltshire & had a great time. 
Having refreshed my Mojo, I called in at my brother's workshop on the way home & we discussed the braking issues.
He agreed, black fluid would point to a seal breaking down somewhere, but there's no visible leaks at the rear drums or the front calipers or any of the valves under the cab, & if it were a seal it ought to be blowing out fluid under pressure. I pointed out the bottle of fluid I've been bleeding into has been stood open on the shelf in the workshop, so is probably full of grinding dust & dirt, although I've half emptied it several times while bleeding. I've been using an old length of black rubber hose & it's entirely possible that that's breaking down of course.
He was surprised my Easibleed pressure bleeder ran at 20psi. Checking his own, it actually says a maximum of 20. I used a half deflated tyre. He uses a completely flat tyre & kneels on the tyre, to produce 5 or 6psi. That would explain mine blowing fluid out from under the reservoir cap. Too much pressure could force air into the brake fluid.
When I mentioned the single "burp" of air from the bleed nipples, he said he had exactly the same symptoms on one of his race cars. Changing the bleed nipples for new ones cured it. Although he didn't think it should make a difference, it worked.
So we may well have a perfectly good pedal pressure & are just introducing a small amount of air every time we bleed it. I haven't tried the pedal while I've been bleeding it, can't remember what it felt like when it was last on the road a year & a half ago, (yes, I do have memory trouble), & I've altered the angle of the pedal since then anyway.
So I'll return refreshed to the workshop tomorrow, flush the bleed bottle out, refill it with fresh fluid, use a new length of clear plastic tube & tackle it again. Onwards.