Brake Failure

[johnben]

Hi Folks

Warming up the E Type on Friday for Drive it Day. Short drive but noticed the brake pedal was moving closer to the floor each time I braked. This was gentle driving and braking, by the time I got home the brake was to the floor, unable to pump. I turned the engine off and after about 10 mins returned to the car and had a full pedal.
Some years ago I had a total brake failure caused by a lot of crud in the system and on inspection of the master diaphragm housing, from which there are 2 rubber tubes connected, one from the rim of the housing and one from the bottom rear pointing back towards the bulkhead. The latter is the one I disconnected for inspection, it was clean and there was still a vacuum evident as I disconnected it. On my previous failure this was full of hydraulic liquid and crud.
I returned to the problem this morning, I had already noticed that I had lost about 1/5 of hydraulic fluid from the reservoir serving the master cylinder, full brake pedal, no noticeable leaks, slave reservoir OK.
I have looked through the previous posts on this subject and would report that I had no white smoke on starting up and that applying the brake made no difference to the engine revs.
All the servo and master cylinder was replaced in 2009.
It is as if the piston in the master cylinder is not returning, I am inclined to replace the master cylinder complete, any suggestions?
Thanks

Johnben (1967 Series 1 2+2)

[mgcjag]

Hi Jon...fluid probably leaking into the resivac tank...Steve

[johnben]

Hi Steve

Thanks for the reply, I have now removed the vacuum reservoir and found it to be dry, I will turn my attention to the brake vacuum servo unit, I read somewhere that you can check for liquid by just undoing the big clip around the cylinder shell cover and gently prising it apart as opposed to removing the unit, but typically failed to make a note of where I saw it.

John 1967 Series 1 2+2

[ralphr1780]

John, take a look at the carpet and felt in the footwell, under the pedal pushrod. This is a common place to locate the missing brake fluid once the master cylinder seals are giving way.

[Herzeg]

Hi

When I bought mine three years ago it was losing brake fluid in a serious way. Took it back to the dealer and he said it was pumping into the servo. He changed it and no problems since.

John

[johnetype]

From your failure symptoms I'd suspect the master cylinder but that doesn't explain the fluid loss. Cracking open the brake servo band to check for fluid in the way you suggest is a good idea as is checking the "lost" fluid isn't the secondary reservoir's gain.

[johnben]

Thanks for the advice folks, I have finally got round to removing and inspecting the master cylinder, I did have to drain the clutch reservoir to do this as the clutch feed pipe fouled the master cylinder.
On inspection of the master cylinder I did find some muck in there so I will go ahead and get a new complete one. I will now turn my attention to the servo unit, slave unit and reservoir and see if I can track down the missing fluid.
I have to admit that MOT's were good for me, I am average mechanics and I found that the tester would give me the 'heads up' on present or future problems, before attending the MOT I used to bleed the brakes as a yearly routine. I have to admit the last time they were bleed was over 2 years ago. This was a rude awakening that neglect is not an option with an E Type.

John Series 1 2 + 2

[johnben]

I have now removed the servo and slave unit, there was some wetness on the diaphragm (both sides) but no fluid gathered at the bottom. I was dismayed to see how much black silt there was in the system, I am guessing, but I would say that this is either from the seals breaking down or the rubber feed tube from the fluid reservoirs.
The top chamber of the check valve shows signs of brake fluid.
My thoughts at the moment are to get a kit for the servo and get new master and slave cylinders complete, along with new vacuum and reservoir feed tubes.
As you can see from the images the brake fluid feed to the slave cylinder is obstructed by the engine frame.
I note that on other E Types this is remedied by revolving the servo a few degrees, is this original?
Please see images below.

John Series 1 2 + 2

[Heuer]

You can rotate the servo by loosening the band bolt and twisting it. Do not over-tighten the bolt afterwards.

[johnben]

Thanks for that David, I am now about to push on and have started another thread regarding the differences in price for the same part.

John Series 1 2 + 2

[johnben]

Hi Folks

I am now at the stripping down stage of the brake slave cylinder, does anyone know how to remove the greenish plastic bearing? The manual helpfully states 'Take out the seal and bearing from the mouth of the slave cylinder'.
The bearing is a very tight fit, I have tried moving the push rod back and forth to tap it from behind without much success, my intention is to put some compressed air into the 2nd outlet from the bearing but I thought I would clear with the forum first, and yes I will put something over the spindle to slow the missile down.

[mgcjag]

Compressed air has worked for me in the past...Steve

[johnben]

Thanks for that Steve, it was too late last night to start the compressor so I sprayed the end with penetrating oil and left it over night, this morning I pulled the push rod and it popped out.

John Series 1 2 + 2

[gtjoey]

I just thought this was an interesting thread to bring back!
Gtjoey13-4