Brake Pedal Push Back

[alanr]

I don't mean the one-way valve that fits in the servo!
There is a metal one-way valve in the line to the servo from the manifold, on a +2 it is in the metal line about mid point that runs across the back of the bulkhead. Probably in the same place on the baby Elan. Just a thought and worth taking it off and checking it works.

Alan.

[mark030358]

Hi Alan,
On the small Elan there is a T piece that connects into the carb. One of the connections on the T is indeed fitted to a one way valve, this is for the headlights onl,. The other connection on the T goes direct to the servo via rubber, then steel, then rubber pipe and connects directly to the one way valve on the servo itself.

Ignoring the vacuum, I should be able to push fluid out through a bleed nipple that is wide open when I pump the brake pedal. The brake pedal should not lock up half way and I dont need vacuum to bleed the brakes. I think the servo is not right, its going back again.

cheers
Mark

[alanr]

Hi Mark,
If you can't bleed the brakes with a bleed nipple wide open you have blockage somewhere!
How about completely eliminating the servo.
If it were me I would make up a short brake pipe to join the two brake pipes that connect to the servo together. A short piece of brake pipe and two female brake union nuts with the appropriate flared ends is all you need.
This would eliminate the servo completely and if you then can't bleed the brakes properly the blockage is in the brake lines, master cylinder or calipers.

Alan

[mark030358]

Hi Alan,
Yes shorting out the servo is an option, my issue here is that too many on/offs is not doing my brake pipe flares any good. Also I know that if I remove the input line brake fluid goes everywhere as its below the level of the MC. I think I will pop off the pipe on the output side of the servo.

But in all honesty I think the piston has stuck in the bore. Also when I tried with the engine running no sounds of any "hissing" when depressing the brake pedal, so I'm also wondering if the air/vacuum valves aren't sealing.

I'm also going to rebuild again my brake MC and swap that again. This is just pants, feeling very sorry for myself

thanks for the help, it is appreciated.

cheers
Mark

[alanr]

Hi Mark,
it is only a car...don't let it get to you!
Sometimes finding the solution to problems can be challenging but it all keeps the old grey matter working which is good!
I know you are convinced it is the servo but you have already sent it back and they have checked it again.
My personal experience with Pastparts has always been very good and i beleive they know what they are doing.

My suspicion now with your problem and you saying you can't bleed the system is that the answer lies either in the Master cylinder or the rest of the system. A Blocked Flex hose maybe or something similar.

Keep at it..you will sort it i am sure.

Alan

[mark030358]

Hi Alan,
So ordered a lot of brake pipe bits and pieces today including a new on car flare tool.

PastParts have been excellent, I am not knocking them as no one deliberately sends out faulty parts. Anyway I intend to bypass the servo with a link pipe and that will prove one way or another where the fault is or isn’t.

I have braided hoses and will check these are not collapsing. I think I would have noticed that though when driving, nevertheless a good suggestion I will take on board. One thing I was thinking about was could it be the speedbleeder, I’ll chnge this back for a standard bleed nipple.



I. Started this in April and it’s still going on, that’s the frustrating part. But it will eventually get fixed I know that for sure.

Thanks
Mark

[Hawksfield]

Hi all
I have had over the years a lot of experience with Girling mk11B servo. I at present use a Girling mk11B servo rebuilt by myself at the first attempt it was ok for maybe a few months then I noticed high vacuum when decelerating an then pumping back, once at traffic lights but was lucky to have spanner handy to release the pressure at the MC pipe fitting.
After some head scratching and research of the servo I came to the conclusion of a sticking control piston. when you brake lightly the control piston should move to the right opening the air valve if it sticks it maintains pressure in the system, it happened to me under light braking. Under heavy braking there is a big difference between the pressure at each end of the control system which manages to effect movement when you lift off.
After which I found the seals available today are not Girling and come in various sizes and materials, one supplier argued that it was correct for the control piston secondary, it was not, when measured against an original Girling seal.
However to cut a long story short l collected a number of sets of seals and all were different sizes when measured. I attempted locate an OE set but nobody could supply. A few years ago I remember reading a comment from a ex Girling engineer that the replacement control piston seals were of incorrect manufacture. the implication was that the material was softer. I eventually replaced the control piston primary seal with seal I had removed from my servo that was fitted OE seals fitted in 1987. I am happy to to reuse the seal as it was in good condition and has been working well for three years.

Mark: I know this will not solve your problem as you have not been servicing the servo yourself. But you are not the first to get a serviced servo back that had this problem, that's why some members have changed to Lockheed servos
This is just my experience and solution. Good Luck
John

[mark030358]

Hi John,
Thank you for your words of wisdom.
I have a few things to try before it goes back again. If on the third time of asking it is still bad I will ask for my money back.

Not sure where I will go from there, probably have to but one.

thanks
Mark

[mark030358]

So, some good news I think.... Long story short...

Expecting the worse and having to remove the servo once more and as the pipes to the servo are soft copper, I bought lots of gear, such as..

i) Banjo's with bleed nipples
ii) New brake pipe flare tool
iii) New brake pipe
iv) Inline connectors
v) Vacuum hose
vi) etc etc

Anyway, before doing anything else decided to go over the whole thing again. Still had a hard pedal mid stroke with bleed nipple open. So small lead hammer, tapped the servo MC casing a few times, also found the screws holding the flange (pipe) to the servo MC were only finger tight. Added some WD40 to the gasket and tightened.

Voila, I had vacuum and no more hard pedal. Took the car for a good 20 mile run all OK. Even dd the photos for the insurance company.

What an utter ball ache. I think perhaps the seals are on the maybe ever so slightly large side on one of the pistons, use will cure this I am sure.

cheers
Mark

ps and thank you to all who sympathized and helped me with this problem. Insurance pics attached...