brakes servo locking brakes on !! help

[123GT-AMAZON]

hi all

ok we have had a restro on the go for past few years just needed the time and nudge to get it finished what with other cars needing doing and work lol

now on this first one we have a 123gt everything went as per normal when doing it some teething problems you would expect and some electrics to sort out when we where ready to test drive car the car went round field fine then on lap back to workshop the brakes locked on !! was late in teh day so we just thought brakes servo no worries bolt on a new one job done when we get time

2 years later and two brake servos on still we have brakes locking on after pedal is pressed it just locks teh brakes up solid all new brake system ie brake lines , brake hoses and brand new calipiers

now for the the second part we been doing a amazon estate and now we have the same problem so two cars sat here doing same issues odd hey

so due to time running out and both cars booked on the car stand at nec we have by passed the servos and all brakes on both fine

now of course it would be nice to get to the bottom of this maybe even have them fixed for drive upto birmingham

any advice would be awsome or past experinces shared to maybe shine a light all i can put it down to is bad luck on servos maybe nos etc just not liking the non use over years so is it a plunge and shell out for two brand new brake servos from simon aint cheap at the best of times 100 pound a pop

thanks in advance

***edit ** also on the amazon estate we are using silcone brake fluid as we had a car go in with someone we use on another car and he got sidetracked on rainy day thought it was drips of rain nope it was brake fluid all over a front end of a 1800 es done a right number on the sweet looking paint job !! so we use silcone brake fluid now as it does not strip , pit nor bubble paint...... and normal dot4 on 123gt

[940_Turbo]

Check the bypass hole in the master cylinder is clear, they silt/rust up when you leave them sitting and if they do the brakes won't release.

Girling servos (I hope you're not using one;-) tend to gradually lock the brakes on after a rebuild. It's caused by not aligning the vacuum chamber properly.

[123GT-AMAZON]

Originally Posted by 940_Turbo

Check the bypass hole in the master cylinder is clear, they silt/rust up when you leave them sitting and if they do the brakes won't release.

Girling servos (I hope you're not using one;-) tend to gradually lock the brakes on after a rebuild. It's caused by not aligning the vacuum chamber properly.

yup its a girling ( defo on the 123gt and one was nos which is on ther now ) and estate has its old original lockhead servo fittted cleaned and painted but still the original

when the servos been by passed the brakes are fine all free so its servo side of things
for sure

[b20e]

The only time I have seen this is when the flexible hoses have collapsed.
I realize you say they are all new, but worth a check?

[123GT-AMAZON]

Originally Posted by b20e

The only time I have seen this is when the flexible hoses have collapsed.
I realize you say they are all new, but worth a check?

with the servo disconnected all is fine brakes work flawless all be it with limits due to no servo being active so im thinking if it was a collapsed hose then it would do it still ? but they work

[Derek UK]

I have a Girling servo that was fully rebuilt by Norton, it's not been fitted, they state explicitly that silicone fluid is not to be used with it so I won't. Some seals like a bit of friction to enable them to flex and seal and I think silicone fluid can be just too slippy in some applications.

The Lockheed servo on your estate would have been fitted after it was sold. Estates with discs, i.e. later ones, had a Girling servo as standard the same as the GT.You infer that the servos have been sitting around a bit and maybe they are just sicking due to condensation induced corrosion. Yes the Girling servo is notoriously fussy about rebuilds. As Peter says, alignment is critical and repair kits had, maybe sorted now, parts that were the wrong size. Diaphragm maybe? Also easy to get the small valve pieces the wrong way round.

[Tony Barrett]

There are two makes of 'Lockheed' servos on the market. There is one type, the cheaper, that you have, that causes problems with Amazons. Buy the 'genuine' AP, only slightly dearer, then no problem.
I don't want to argue about the info, but experience does sometimes beat the labels and the pound notes.
An interesting anomally, a friend has sold over five hundred of the cheaper ones, to fit Triumph sports cars, and had no reported problems. Also, one of the cheaper ones that I had, gave trouble on an Amazon, but when it was fitted to an Alfa no trouble!
It doesn't really matter why, and the reason may never be found, but you now have the info to save money, and time, and be safe.
Tony Barrett
The Old Volvo Man

[123GT-AMAZON]

ok a update is now at hand we found out the problems on both cars it was the master cylinders so two new ones fitted and bleeded the brakes corrected the problems so glad to get them fixed , we will connect the servos back up at a later date when we have time

[940_Turbo]

You can unblock the balance hole.........

[123GT-AMAZON]

was just easier this way and peace of mind it has new master cylinders
we have kept the old cylinders to look at at a later time