Bleeding Brakes!

[thescrapman]

Today we have been mostly getting very p****d off with the brakes on our RBRR steed. Our inability to get them working has caused the cancellation of the 3rd MOT booking. It is a '68 Mk1 2000.

Best we can manage is 5 pumps of pedal to produce enough pressure to slow the car down. Sadly not up to MOT standards.

Assistance required please.

A quick history. When we collected the car, no fluid in reservoir, and pedal went almost to floor, but brakes would slow the car. Fitted repair kit to master cylinder as we found the seals were breaking up. Also found calipers were seized so resealed. Adjusted rear drums. Refitted to car and after 5 minutes of pumping pedal fluid started flowing through system and then bled brakes all round. Pedal goes straight to floor when tested. Brake fluid dripping profusely onto pumpers feet. Removed servo (leaving master plumbed in, and drained out a pint of old brake fluid. Now know wher it has been going to out of the master in the past). Refitted servo and rebled a few more times. still rubbish. Rebuilt rear cylinders. replaced front flexihoses. Bled again. still bad, used Gunsons Ezi-bleed. No air coming out, but pedal still to floor.

5 quick pumps gets the pedal to go hard after about 2 inches of movement. If engine is then started, pedal sinks to floor so servo is assisting OK it seems.

Undid nuts holding master on, and proved that the first inch of pedal movement is the play before the operating lever contacts the piston. removed master, still plumbed in and I can push the piston in and out 3/4 inch easily with a screwdriver.

Disconnected plumbing and drained master. Took the parts out (took attached picture, I think the silver washer is in the wrong place in the photo, it was at the other end of the piston when installed. Please tell me if there are any parts missing!!!!) and refitted. Refilled master and pumped piston in/out by hand.

I would have expected fluid to be expelled out of the exit under force, nothing, but I do get a few drips if I wait long enough without pumping the piston. Tried rapid pumping again, still nothing. This would fit with my efforts to start it bleeding in the first place.

I found a diagram of a Stag master on the messageboard, courtesy of Mr Carruthers I believe, and that seems to indicate that I have put the kit together right, though my repair kit has a different 1-way valve arrangement. The spare Mk2 PI Servo and master I dismantled was different, more matching the diagram.

If I have read it right, as the pedal is pushed, the one way valve seals the end of the cylinder off (should there be a rubber washer at the bottom of the bore?? ) and then fluid is forced through it by the piston.  As you lift of the pedal, the bore is refilled from the reservoir.

But how does the air in front of the rubber cap thing on the piston end of the spring get out? How does the air behind it escape? The diagram shows a bleed passage, but all I could detect with a bit of 0.6mm welding wire was the main fluid passage, is it a very tiny hole?? If It was blocked might we get the symptoms we have??

We have now resorted to buying another 2000 to 'borrow' parts from to get us going.

All guidance much appreciated.

Cheers

Colin

[Nigel]

Had some major ag on a 2000 that had been off the road for some time
resealed the master but ended up having to replace the whole master cylinder with a new old stock item pedal creep (OK at first ) but after a few miles the master cylinder kit was chewed up on a knacked bore or the rubber failed!
also had some probs with the front hoses not bleeding fluid but as you have changed them this should not be the problem

[Beans]

Hi Colin,

I am not familiar with the braking system of a 2000 but the mastercilinder looks as if it should work more or less like the clutch master cilinder on a TR7  ::)

Normally if you press the pedal the first thing that happens is that the connection between fluid reservoir and cilinderbore is closed by a small seal and thus the fluid is forced into the brakes.

If this doesn't work (seal knackered) you will be pumping (part of the) fluid back into the reservoir instead of into the brakes. So first check what happens with the fluid level in the reservoir when you press the pedal.

Good luck with it,
Theo

[shenderson]

When bleeding the system from empty I start by removing the drums, releasing the self-adjusters (on a MK 2 or Stag, or wind off the adjusters all the way on a MK1) and pushing the pistons all the way in.  Also push the front caliper pistons all the way in.

This minimises the possibility of air bubbles remaining inside the cylinders when fluid is being bled through.

Then bleed each cylinder in turn, starting at the nearside rear and working through the others in turn.  It takes at least two or three gos at each cylinder to get it all out.  There is no point trying to bleed each cylinder completely in one go, because as fluid passes a Tee-piece, it will draw air in from the other line.

If you are still left with a soft pedal, try wedging a length of wood as hard as possible on the pedal and leaving it overnight.  This will pressurise the system and force any air bubbles to the top.

Hope this helps...

Steve

[GT6DavidMK1]

Hi Colin,
I have a spare brake master cylinder off a Triumph 2000 so if required give me a call.

Regards David.

[thescrapman]

David.

I might give you a call in a few weeks.

I have a 2.5 master on it at 45 degrees at the moment, and it has proven the fault to the master.

I am going to borrow the master/servo from the car I am going to be storing for a local TSSC member as a stop gap. But I will need to fix that before it gets sold.

Would anyone be interested in a 30k from new 1965 2000 saloon???

Cheers

Colin