Bleedin' brakes!! Arrghhhh!!!

[markcro]

Right I am just short of pushing my GT6 out into the road and burning it out!!  :B

Last month I fully rebuilt the front brake calipers and refurbed the rear brakes. When I put it all back together and bled the system I found that the brake pedal would go to the floor.

- I rightly or wrongly diagnosed the problem as the Master Brake Cylinder seals had gone. As pressure would build if you pumped the brake pedal.

- So new Master Brake Cylinder fitted. And over two weeks I have put 2 litres of fresh brake fluid through the system and tried every which way to bleed it............... but the pedal still goes to the floor...  :X :'(

There are no leaks, and even if there was I would expect fluid to be squirting everywhere with the pedal going straight to the floor without any real pressure........... :-/

This can't be an issue of air in the system as I have bled it in so many ways and with so much fluid. And even if there was air in the system I would expect somewhat of a pressurised pedal if not a bit spongey. But there is nothing.  :(

So any suggestions?

When I press the pedal and it goes to the floor I do hear a click or pop type noise coming from the brake servo area. Is that normal?

All this lovely weather and I had planned to have the car on the road two months ago! grrrr!

[Royboy66]

Mark
If you have a servo fitted ive heard they can fill with brake fluid when they fail!  
can you bypass the servo to try see if its that?
Or take servo f
off and give it a shake, see if its hiding all that fluid  !! ;)

Roy 8)

oh and put the matches away!   ;)

[markcro]

Thanks Roy, but the thing is that I'm not loosing any fluid either. I could pump the pedal all day long and it will go to the floor, but the level in the reservoir will remain the same.
I was going to use petrol leaking from it's crappy "new" fuel pump and a Zippo lighter! :P

Okay I will try the servo and see what happens. To bypass it I will need to buy brake lines etc. to link up the line?

[Blubayou]

Hi Markcro,

Are we saying the fluid level remains the same when trying to bleed it?

If that's the case I'm thinking is the pushrod on the MC set up too tight? This could stop the cylinder returninng all the way back to allow fresh fluid in.

[markcro]

No, no, I meant that when everything is done up tight that I don't loose any fluid. But yet the pedal goes straight to the floor.

When I was bleeding them I passed a full 2 litres of fluid through the system. And fluid isn't exactly cheap.  :-/

[Royboy66]

Oh. If the fluids not dropping in M/cyl when you press pedal, it may not be servo.
Yeah check Mcyl working ok.take rubber boit off and check actuating rod works ok!  

[markcro]

This is a pain in the hole. I just painted the bulk head so it is all nice and shiney. So if I have to take off the brand new master cylinder and mes sit all up again....  :'(

[Velocita Rosso]

Have you pumped the pedal and quickly checked the m/cyl for any bubbles coming back up?
Have you done anything to the brake cyls ?

[markcro]

michael_charlton wrote:

Have you pumped the pedal and quickly checked the m/cyl for any bubbles coming back up?
Have you done anything to the brake cyls ?

I have pumped the pedal quickly but didn't check for bubbles. I will do that. What will it mean if there are bubbles?
I rebuilt the front calipers with new seals and 4x new pistons. I was thinking that maybe something is wrong there, but then again with the pedal going to the floor there should be puddles of fluid on the ground or wheels if the piston seals were leaking...??
I'll give them a look anyway.

[GT6 M]

on the end of the rod in the MC there is a wee rod wid a spring aroond it, ont end of this is a rubber washer. follow,!!!
this rubber washer  / seal,  seals the end of the hole in the MC, so allowing fluid to go to brakes..

If ye aint got this sealing reet, or put it together wrong, then this will be the syptoms you are getting.

Have a deek at a  picture of the internals, or take the old one t bits, and all will come clear as Brake Fluid
;) ;) ;)

M

[Fred101]

This is likely a stupid question but no one has mentioned it yet.

Are the brakes themselves adjusted up correctly? Especially the rear (I think the fronts are self adjusting).

If for example the rear brake adjusters aren't done up tight and then backed off a little, you could be pushing lots of fluid through just to move the shoes a huge distance and then running out of pedal travel.

[markcro]

Thanks guys.

- This is a brand new MC that I bought and installed. (I bought the rebuild kit for my old one and then thought to myself that I may as well eliminate all doubts of it working or not....  :o )
But I suppose it is possible to get a faulty one off the shelf.

- The back brakes are all done up tight against the adjustors.

[thescrapman]

Are you saying that it you pump very quickly on the brakes, you get a hard pedal, but then a press shortly after goes to teh floor?

Cheers

Colin

[Velocita Rosso]

Getting bubbles doesnt necessarily mean theirs a leak eg fluid going somewhere, but it does mean you are sucking in air from somewhere
How old are the brake cylinders at the rear?
If you have a servo have you had this checked?

[markcro]

thescrapman wrote:

Are you saying that it you pump very quickly on the brakes, you get a hard pedal, but then a press shortly after goes to teh floor?

Cheers

Colin

This is exactly what I was getting on the original MC. But now with brand new MC is only slightly firms up after pumping.

[markcro]

michael_charlton wrote:

Getting bubbles doesnt necessarily mean theirs a leak eg fluid going somewhere, but it does mean you are sucking in air from somewhere
How old are the brake cylinders at the rear?
If you have a servo have you had this checked?

I would say that the rear brake cylinders are 39 years old! ;) But surely these would be leaking fluid and quite alot if they were the cause of the pedal going to the floor?
The servo is also original. I haven't touched this.

[thescrapman]

It sounds just like air is remaining trapped somewhere.

When faced with this in the past I made up a filler cap with a tyre valve in the middle, then used an assistant to very slightly pressurise the master with a foot pump or bike pump and gently force bleed it.

Same principle as an eazi-bleed but for tight-wads.

I would also remove the pads and allow the pistons to move in a bit, then return the pistons with the bleed nipple open but the pedal down a bit to ensure all the excess fluid went out the bleed nipple.

On the rears I would do similar and allow the piston out slightly (very easy to pop it out so be careful!)

Cheers

Colin

[Nick Moore]

Quick question - does the new master cylinder have 'TRW' on the side? A lot of TR owners have had trouble with these. Reconditioning the original might be a safer bet.

[Falkon]

Is this by any chance a dual braking system like on US cars. If so the clicking would be the PDWA valve, and it could block off the fluid from the side w/ air in it. It needds to be centralized to bleed properly. It's a big pain.

[GTRoger]

Indeed, if it's a dual system, check your PDWA valve for internal leaks. I had the same on my PI. Turned out that some bits inside the PDWA were missing (still a mystery!! ) and therefor brakefluid was pumped round in circles but not building up pressure.  

[markcro]

The ease and lack of pressure that the brake pedal goes to the floor would mean that the system was full of air, and after two weeks and 2 litres of fluid I can't see that could be??  Even if it has a caliper full of air I would expect a spongy pedal but at least some kind of pressure??

Yes the new MC is TRW. If this is a case of the new MC being faulty I will go mental!!  >:(

I am not sure if this is a single of dual brake system. How do I tell? There is only one line coming out of the MC. (late 1973 GT6 Mk.3)

[GTRoger]

One line is a single system. You can check the MC simple by blocking off the outlet line. If your pedal still goes to the floor it's the MC.  

[rotoflex]

The dual line brake system has a master cylinder that looks like the one below; the single line brake system has a master cylinder that looks like a larger version of the clutch master cylinder.

[markcro]

Okay thanks. Mine is definitely a single line system so. Just a bigger clutch master cylinder. I will test the MC as stated above. I'll try it at the end of the line as far away from my lovely new paint work as possible!  ;)

[shedmonkey]

Had a similar problem once it was a tiny bit of grit stopping the flow back as per GT6M describes (it was a 2000 master but similar principles) did you strip and clean the "new" master before fitting they can sometimes have shelf shite in them I never fit hydraulics straight off the shelf I always strip and "lube" up (one for smithy there) before reassembly and installation ...it also ensures the spotty YTS lad put the thing together right in the first place!