61 replies to this topic

[minimat]

Only the 0/s/r is adjusted the opposite way because they are threaded into the backplate and simply screw in,the fronts are not threaded,this is a very odd problem,i assume the brake system is standard as per 1964 and not been upgraded to a split master cylinder system? 

[Spider]

With the front brake flexis clamped we get a good pedal.
If the back flexis are block off there no pedal.

While I was at work today my dad had taken his master cylinder off and checked it, all still like new

 

Ah, OK, I think I may see the issue here.

 

I'm guessing you guys are bleeding the brakes the old school way (which is damn good IMO) of pedal down, open nipple, fluid / air comes out, close nipple, peddle up, peddle down and the cycle repeating?

 

If you are, then it's likely you are shutting off the rear Pressure Shut Off Valve, so when bleeding the rears, the valve is shutting off and all that's being bled from them is residual pressure between the valve and the wheel cylinders, You would get there doing it this way, but takes ages.

 

If this is what's going on, just modify the process for doing the rears by opening the bleed nipple, then peddle down, hold, close nipple, peddle up and repeat the cycle from there.

[monkey]

With the front brake flexis clamped we get a good pedal.
If the back flexis are block off there no pedal.

While I was at work today my dad had taken his master cylinder off and checked it, all still like new

 
Ah, OK, I think I may see the issue here.
 
I'm guessing you guys are bleeding the brakes the old school way (which is damn good IMO) of pedal down, open nipple, fluid / air comes out, close nipple, peddle up, peddle down and the cycle repeating?
 
If you are, then it's likely you are shutting off the rear Pressure Shut Off Valve, so when bleeding the rears, the valve is shutting off and all that's being bled from them is residual pressure between the valve and the wheel cylinders, You would get there doing it this way, but takes ages.
 
If this is what's going on, just modify the process for doing the rears by opening the bleed nipple, then peddle down, hold, close nipple, peddle up and repeat the cycle from there.

Sorry to question you but is Adam not saying pedal is good with fronts clamped but bad still with rears clamped? Surly this points to air in the fronts whereas your reply is indicating air in the rear?

Forgive me if I'm wrong, just trying to understand myself!

Is it worth trying with just one of the fronts in turn clamped off to see if it's both or jut one causing the issue?

My suggestion would be to try bleeding at each end of the link pipe between the two front cylinders, but I may be wrong!

[Spider]

Sorry to question you but is Adam not saying pedal is good with fronts clamped but bad still with rears clamped? Surly this points to air in the fronts whereas your reply is indicating air in the rear?

Forgive me if I'm wrong, just trying to understand myself!

 

 

Apologies, you are right, I mis-read the post.

 

And as you've suggest, I would agree, there seems to be air in the fronts.

[adam_93rio]

It does seem like there is air in the fronts still, but literally nothing but fluid coming out of them.

Tried the shouting up and down at each other method.
Tried pumping the brakes a few times then holding on the last one and opening and closing the nipple.
Tried easy bleed
Tried every way I can think.

I will have a go at bleeding the link pipes, and get messy no doubt.

I do believe it is still a single line system,
This picture confirms that(?)

[Spider]

It is a Single System.

 

If you're bleeding them and there's no air at all,you have the piston springs in place, then it can only be adjustment.

 

Try clamping off one side and then the other to see if it's one particular side.

 

Also, to check if it is an adjustment issue, remove the drum from one side and clamp the shoes in place, so they can't expand out, then try the peddle, it should be rock solid. If not, air is getting in somewhere. I'd be looking at the new wheel cylinders.

 

If that comes good, then fit the drum and wind each adjuster out as tight as they will go (without being silly, but the brake will be locked) and try the peddle again, it should be rock solid. Then you'll know where to look closer.

Edited by Moke Spider, 31 May 2016 - 10:25 PM.

[adam_93rio]

So, wound the adjusters solid and the pedal is about an inch and half off the floor. Wound them all back ever so slightly and the pedal stayed there, there's a lot of movement in the pedal before it feels good.

Going to have a go at bleeding the link pipes tomorrow, as we get a slightly higher pedal on the second and third pump.

So things are looking up slightly, hopefully there is just a stubborn bit of air left in he link pipes.

I was very surprised with the adjustment. If anything, they're still a little tight now. But when you say sensitive, you weren't kidding!

[Spider]

Thanks for the feed back.

 

Q. Did your Dad measure the MC Bore when he had it out?

 

Given each wheel cylinder is around 1" dia, there's 4 of these and the MC is cira 0.7" and it also has to 'fed' the rear brakes, I think you may start to see where and why the brakes are so sensitive to adjustment.

 

Good result, but certainly does seem to be air in the system. At least I think you guys can see where you need to go.

 

Can I suggest, given the wheel cylinders are new, back one adjuster off at a time and give the pedal a good press, then adjust it up and move on to the next. This may wet up and help seal the new cylinders, as they maybe dry and allowing some air in when bleeding.

 

<EDIT: Jumping ahead a little here, the peddle may not get 'rock solid' until the car is driven a bit and the brake shoes are bed in, then further adjusted. None the less, before you get to this point, it should be well off the floor. >

Edited by Moke Spider, 01 June 2016 - 08:50 PM.

[timmy850]

Out of interest, which bore front cylinders did you buy?

There is GWC 102 / 103 with a 0.8125" bore

There is GWC 126 / 127 with a 0.9375" bore

 

And, do they correctly match the bore on the rear cylinders? 

 

There is a list here of the standard front/rear/master cylinder bores

http://www.minispare...rt.aspx?1~9~105

[adam_93rio]

Is it possible for the brake master to be intermittently faulty?
The other day when we strapped the front brakes closed, and pressed the pedal, it went solid. (Same as when I adjusted them solid)
Today, took the drums off and put a strap round all of the shoes, to hold them in to make sure there was no air in the wheel cylinders.

Strapped them up, put the easy bleed kit on, bled all the brakes.
Before the straps came off I pressed the pedal just out of interest, and it went straight to the floor, and I can see fluid squelching around in there through the plastic cap.

So I think after all of this, it's the master cylinder. Seems strange that it was literally working when we moved it on the drive to an area to jack it up. And now it doesn't

[Spider]

There is some big forces exerted to the shoes, maybe the strap isn't enough to hold them back?

 

Try it again with the drums on.

[adam_93rio]

There is some big forces exerted to the shoes, maybe the strap isn't enough to hold them back?
 
Try it again with the drums on.

Straps didn't budge, they were still very tight when we took them off.
Will give it another go with drums on but it was exactly the same problem as we've been having

[Spider]

I hope this doesn't come across the wrong way.

 

I see that you guys have set yourselves up to do a pressure bleed with a Gunsons just the other day when this problem was noticed, yet a few days prior (with the brakes adjusted hard on etc) there was seemingly a reasonable pedal.

 

Sorry to pry here, but it sounded like you were just about there with the bleeding, so why did you guys feel the need for the pressure bleed?  Did it get spongy over a day or so, or feel spongy from the start?

 

Also, can I ask why you guys are strapping the shoes back and not fitting the drum at this point? Is it so you can look for leaks? Keep in mind, 99 times out of 100, the higher the pressure in the system, the less likely it will be to leak, unless the cylinders are rusty of course.

 

Also, when bleeding the system, are you using a clear plastic tube (perfectly clear) and bleeding in to a clear jar? I ask, because this is the best way of seeing if any air is coming out. If there's no air coming out, then it would be an adjustment issue, if there is air, then it's hydraulic, though, given it's good then bad from one moment to the next, it does sound hydraulic.

 

In normal operation, in the fist few mm of pedal travel, there is a small amount of fluid pushed back in to the reservoir of the MC, but that should be all.

 

Given how much you guys have bled it over the past week or so, I'd be say if there was any air coming out of the system when bleeding, then the Master Cylinder would be the likely culprit, BUT I'd also strip down the wheel cylinders too (I'd actually be doing this first at this stage). Just because they are new, doesn't mean they won't give trouble.

 

The way all these seals in the brake system work, they can draw in air without leaking (and this is why they shouldn't be vacuum bled), when they get real bad, they will leak.

Edited by Moke Spider, 04 June 2016 - 09:48 PM.

[adam_93rio]

I hope this doesn't come across the wrong way.
 
I see that you guys have set yourselves up to do a pressure bleed with a Gunsons just the other day when this problem was noticed, yet a few days prior (with the brakes adjusted hard on etc) there was seemingly a reasonable pedal.
 
Sorry to pry here, but it sounded like you were just about there with the bleeding, so why did you guys feel the need for the pressure bleed?  Did it get spongy over a day or so, or feel spongy from the start?
 
Also, can I ask why you guys are strapping the shoes back and not fitting the drum at this point? Is it so you can look for leaks? Keep in mind, 99 times out of 100, the higher the pressure in the system, the less likely it will be to leak, unless the cylinders are rusty of course.
 
Also, when bleeding the system, are you using a clear plastic tube (perfectly clear) and bleeding in to a clear jar? I ask, because this is the best way of seeing if any air is coming out. If there's no air coming out, then it would be an adjustment issue, if there is air, then it's hydraulic, though, given it's good then bad from one moment to the next, it does sound hydraulic.
 
In normal operation, in the fist few mm of pedal travel, there is a small amount of fluid pushed back in to the reservoir of the MC, but that should be all.
 
Given how much you guys have bled it over the past week or so, I'd be say if there was any air coming out of the system when bleeding, then the Master Cylinder would be the likely culprit, BUT I'd also strip down the wheel cylinders too (I'd actually be doing this first at this stage). Just because they are new, doesn't mean they won't give trouble.
 
The way all these seals in the brake system work, they can draw in air without leaking (and this is why they shouldn't be vacuum bled), when they get real bad, they will leak.

No worries, the other day when we tried the gunsons kit the seal had gone within the cap and it seemed to have blown air into the system, so a new kit has been purchased and is the reason we were rebleeding it, just in case.

The best the pedal has been is pumping it twice, then getting a pedal feel about an inch off the floor, which isn't good. That's with the system bled and adjusted slightly too tight.

The reason for holding the shoes in as far as they will go with straps is a hint someone had given us, and so we thought we'd give it a try.
Reasoning behind this is that a few people had written on another forum vouching for this method when trying to bleed drums when there is some stubborn air trapped.

the main reason it seems like we're going round in circles is basically because we are. I've bled brakes up countless times, fitted new systems etc. Never had this much trouble with getting a pedal. When something is faulty, it's usually obviously faulty.
It's probably that it's being overthought, trying to get this done is breaking our minds and spirits a bit, I just can't think straight because it's so stubborn.

In the morning I will show a video of what I mean with the master, it didn't seem like it just backed up for the top of the pedal travel. But whilst pressing the pedal down, seemed to be swirling quite a lot, all the way down to the floor

[adam_93rio]

Oh, and there was a slight amount of air in the system when using the gunsons kit today, from a back wheel cylinder.
We are using clear tubes so we can see what's coming out, the back ones are into a beaker which we can see from the top, the fronts are both in clear jars (ran out of clear containers in the garage)