brakes locking/servo?

[Deleted]

how can i determine wether its the servo locking the brakes? and whats the cure if it is ? i recently rebuilt the servo with a new kit as it was leaking,could this be the problem?

[stantondavies]

Yes. If the brakes lock on and won't release for 20 mins or so, then this is exactly what happened to my 3litre after I had rebuilt the servo. It took TWO replacement/rebuilt servos to cure the problem and I still don't understand what was wrong. Good luck.

[Phil Nottingham]

It was fot this reason and converted to the modern and reliable Lockheed 7 as used on P5B P6's and later later Land rovers amongst may other cars

[dorsetflyer]

It's interesting about the reliability of the Girling Brake Servo, as the photo of the one that failed I put in on the other thread was the original fit, and that lasted forty one years. I hope the new one now fitted lasts as long.

[Phil Nottingham]

I wonder if its to do with its location on P5's (and P4's) as it low down under the manifold on both

[dorsetflyer]

That is a good possibilty, I don't know of any other car that has them fitted so low down. Most Servo's are fitted on the line or above the line of the master cylinder.
Any other thoughts on this.

[Phil Nottingham]

Yes its so low it almost drags on the road - not like your Snipe set up at all

By the way to check whethe its is the servo thats locking the brakes it can be bypassed - this is not very easy though due its location and of course the brakes will be very heavy so do not road test

[Deleted]

At last an answer!!!

I should have searched for this site earlier. Im having a nightmare with the brakes on my P5 at the moment. If the pedal is pressed the brakes lock on. The only way for them to be released is by undoing the bleed nipple on the calipers. Does this sound like the Servo? Many thanks.

[stantondavies]

On mine the brakes released themselves after a peroid of about 20mins. So there may be more than one problem here.

[Phil Nottingham]

That is a sympton of failed Girling servo but check the free travel on the master cylinder first - then recondition it if no improvement

[Deleted]

Another cause for locking brakes after a rebuild of the MKII Girling servo is that parts in some rebuild kits cause them to stick!

The kits contain a foam rubber extruded rod that fits behind the leather vacuum seal on the large piston that slides in the vacuum cylinder. If you are unlucky like I was, then this foam rubber rod will be too large in diameter or not soft enough so that it presses the leather seal against the cylinder to tightly. The result is that the vacuum piston moves when you apply the brakes, but the spring can't return the piston when you release the brakes.

The solutions are to a) keep the original foam rod behind the leather seal, b) slice some of the thickness off the new rod or c) get another kit.

[dorsetflyer]

Or alternatively get it rebuilt by specialists. At least you can get a twelve month warranty with it, and most importantly make sure it has been pressure tested, as this will highlight any faults as you describe and can be fixed before it is returned to you.
I wouldn't dream of just getting a kit and doing it myself, mainly because of a safety issue. If it goes wrong at least you can blame someone else and not yourself.

[Phil Nottingham]

I do agree - it can be very false economy especially if it does fail and you have to take it off again

[Deleted]

I did not fit foam rubber rod at all and servo works fine for almost 15 years. Theo Potma

[Deleted]

i presume that if the servo or master cylinder set up are at fault all 4 brakes will lock ? i need to check but think this is mainly affecting the fronts only ! more likely flexi pipes? i will be stripping it down this weekend and hope its the flexis .

[Phil Nottingham]

Flexis are always supect but the braking effort is biased to the front so these do lock very easily with Servo faults as the rears are not that effective under partial pressure

[Deleted]

just to let everyone know new servos fitted and is working fine. thanks all for the advice

[Phil Nottingham]

Good - just to sort out your starting problems now.. Do not dishearten we've all been there!