Serious brake bleed issues

[keithmac]

Hello All,
I am at the end of my rope. 15 month restoration, now ready to go but a stubborn soft pedal is stopping me from driving.
Some history, new master ,servo,lines forward of the IRS including all flex lines, front calipers ,rotors. No leaks. Dot 5. System is later Type 2
First bleed - gravity on all, seemed to work well.= soft pedal ( two pumps )
Second bleed-vacuum bleed= soft pedal
Third bleed- syringe all four from reservoirs two full for each reservoir= soft pedal
Fourth bleed- pedal pump on all four= soft pedal
fifth bleed - loosen pipe connection at master to servo-bleed three pedal pumps=soft pedal
Clamped off the rear flex line ,pedal still soft. Cant clamp of the front , they are braided.

I wish I had known to bleed the master and servo prior to install to completely eliminate them as a source of the air trap but was unaware .
The car will stop but there is a real noticeable difference between first and second pedal pump.
I have scoured every post on all sites and have no answer that seems to fit.
Summer is drawing to a close soon and I would like to break this engine in---safely, with brakes
HELP !
Keith

[mgcjag]

Hi Keith....try one valve at a time.. tube on valve into a jar...open valve ..press pedal down and hold down..close valve.....release pedal..repeat till no air bubbles see comming from each valve..........pumping the pedal can cause air bubbles to just move up and down in the system..... Steve

[288gto]

Hi Keith,

Sorry you are having so much trouble. I know Chris Vine on here had a few problems bleeding his new system with dot5 silicone fluid.
Apparently it aerates more easily. If I recall he spent more time letting it gravity bleed. It might be worth looking through his blog. www.etype.crisvine.com

I know on my new system with all new components it took a good few goes using gravity, conventional pedal pushing and vacuum to get it air free with DOT5.1
I also had to let plenty of fluid out at the servo unions.

Probably not what you want to hear but just keep trying and perhaps give more time with the silicone fluid if it is prone to aeration between bleeds to let it settle?

Best of luck


Simon

[keithmac]

Thanks Simon,
you say you had to let plenty of fluid out at the servo unions. Did that include the servo union from the master?
It is the only place I have not bled and seems like it might be an air trap but I have not read any blogs about this being done.
I will attempt it tomorrow. I have gone through a quart of dot 5 so far !
Sorry Steve , I should have been more detailed in my first post the pump ,close bleed valve, open valve, pump
on individual brakes , in order , was done.
Regards,
Keith

[cactusman]

You will get there. Only thing I would add is when you pump really stamp hard on the pedal till the bottom then shut the bleed valve and release pedal. Obviously you need a pal doing the stamping or the bleed nipple. Gentle pedal presses tend to move fluid past air locks. A hard stamp stands a better chance of moving the lock further along or out.

[Tom W]

Have you stripped and rebuilt the rear calipers to completely get all the old fluid out? If you have Girling calipers, the inlet and outlet to the cylinders are both on the top, so bleeding alone won’t flush the old fluid out of the system.

[288gto]

Hi Keith,

Yes the union from the master cylinder to the servo, I got quite a lot of air out there. I suppose you could think of that as a separate circuit in itself.


Best of luck,


Simon

[JerryL770]

Two thoughts,
1. Some calipers have a crossover pipe from one side to the other. This must come from the top of the inlet side to the bottom of the other side. If you go from top to top and then bleed at the bottom, you are unlikely to get the air out of the second side.

2. Consider using a pressurising system to pump the fluid rather than a suction system (or pedal action) which can pull air through any possible leak point.

[keithmac]

Good suggestions all
I wonder , would it make a difference if the engine was running? surely the servo must act differently, perhaps help in getting some trapped air out of there?
So here is the new plan, crack the pipe at the servo from the master, force fluid via syringe from the reservoir flex hose through the pipe.
part two. close pipe , start car, open far front bleeder , stomp pedal ,close bleeder repeat and pray.
What do you think?
Cheers
Keith

[johnetype]

No stomp. Anything to do with brake bleeding must be gentle.

No engine running either as having the servo move is an added complication.

2. Consider using a pressurising system to pump the fluid rather than a suction system (or pedal action) which can pull air through any possible leak point.

Absolutely.

[JagWaugh]

About a week ago I helped with a car which had a new M/C and servo fitted, but nothing had been bench bled.

I used a large syringe with a bit of a rubber bellows (sealed on the ID of the reservoir, and on the bevelled end of the syringe) to pressure feed from the reservoir. It doesn't take much pressure.

I filled the reservoir and let it sit for gravity to work a bit, then used the syringe to pull a vacuum in the reservoir. This pulled a bubble out of the line, which the filter sock trapped. Tapping on the side of the reservoir helped remove the bubble.

I alternated between pulling a vacuum and getting rid of the bubble, then applying a bit of pressure for about 10 minutes.

After another 10-15 minutes of that I went on to bleeding the downstream system. Pedal was hard after about 30 min of that.

[keithmac]

Hi John
The syringe technique of pressure bleeding has been thoroughly done ( third bleed ) Two full syringes on each front and rear. Hence my desperation in try a different technique .
I notice my servo is about 5 degrees rotated to the left side of the car. ?
System has no leaks.
sigh...

[Tom W]

I would also try pushing all the pistons all the way back into the calipers before trying the next bleed.

[JerryL770]

The kind of leak that allows air to be sucked into the system does not necessarily show as leaking fluid externally to be seen.

I've had this kind of problem in the past with a Cooper S and others and it was always cured using a pressurising method, wherein you pressurise the whole system by pumping air into the top of the fluid reservoir. We have a product in the UK called Eezi-bleed and its a one man operation which you can complete in a few minutes.

I've even done it with some flat rubber (cycle inner tube) and flat plate with a tube inset clamped on the top of the reservoir - most recently on my Facel Vega HK500 when I did not have a proper cap to fit the reservoir.

I'd be surprised if this does not work.

[288gto]

I’m sure others have managed without a problem pressurising the reservoirs but I was reluctant to do this given that some of the replacement reservoirs supposedly made to the original spec split if you just look at them. Mine are original and I was still reluctant.

The OP is using silicone fluid so not a problem with paintwork but having spent a fortune on having the shell painted I didn’t want to risk it with 5.1. I know you can clean it off straight away and it shouldn’t affect the paint.


Simon

[keithmac]

So I am thinking the syringe technique should be the same as the pressurization technique- forcing fluid through the system. I have cracked the main pipe at the servo from the master, carefully forcing 100ml of fluid freely through the union. No air seemed to escape
Repeated the process with the right front then left front brakes, 100ml through each .no visible air bubbles in attached tube loop ,reattach reservoir careful not to introduce air ANYWHERE.
Test brakes....soft pedal. notable difference still between 1st and 2nd pedal pump
Grrrr......

next step...sell the car

well maybe just jack up the rears , remove the wheel and repeat this procedure to them..
for the 6th time
What was that definition for insanity again? Doing the same thing over and over again, expecting a different result?

[johnetype]

Position of the servo is not absolute, it just depends on the relative position of the two halves before the band was tightened up. I doubt if it's adding to your problem but if the 5 degrees out of vertical bothers you you can slacken the band and rotate the forward half of the servo as you wish noting that if the brake lines are still connected they'll have to bend as well.

Iirc, mine is slightly off vertical since new but I'm not able to check right now.

[mark10337]

I remember that once when the garage were bleeding the brakes, they had a devil of a job. Pressure systems, traditional method etc. etc.

Only when we created vacuum did the system bleed properly and the whole thing was done in minutes. Just a thought for you.

[keithmac]

Thanks All,
I Have tried a vacuum bleed system ( 2nd bleed ) although it is not " professional grade" equipment .
I have been advised to remove the new master and bench bleed it .
For lack of any other plan , I will give it a try and report back, I fear it will need another full system bleed when I'm done.
If it works , I will detail the procedure,
Cheers
Keith

[mark10337]

ah, by creating a vacuum I meant having the car running in neutral rather than a vacuum bleed system.