Brakes staying on

[englishmaninwales]

1966 S3 single circuit brakes with servo. Brakes stick on momentarily after application then release. I thought it might be the master cylinder so I replaced it and bled the brakes, but still misbehaving. My next thought was to overhaul the front calipers as the car has been standing unused for a long while and I considered the pistons/cylinders may be corroded. But as the effect is equal I wondered about the servo as the cause? To test can I bypass the servo with a union between in/out ( and bleeding after) and test? Obviously I ll need to press harder!!
Thanks
Malcolm

[richardcox_lotus]

Yes that is the test !

This is not an unheard-of complaint. Check the archives. And it's nearly always the servo rather than m/c or calipers.

[Pistacchio sprint 72]

I have the same problem. Should we get rid of the servo (also called mastervac?)

[billwill]

I took my servo out of circuit many, many years ago. More trouble than it is worth. An elan does not need a brake servo, but best to get the softer brake pads when you take it out of circuit.

[AHM]

I had the same problem.
Rebuilt M/C
Rebuilt calipers
Rebuilt servo
discovered that if I hooked my foot under the pedal to pull it up the last bit it didn't stick
Rebuilt M/C again
The problem persisted and operating the pedal by hand I could feel the friction of the last bit.
Oiled the pedal box - No improvement
Took the pedal box out - everything free

On re-assembly I discovered that the alignment could be altered by moving the aluminium end support bearing.
Problem solved!

[theelanman]

mine do the same.....
I haven't found he root cause yet but suspect my servo orientation.....
if you have a Lockheed servo then check it orientation as this is know to cause 'slow' brakes....
I had posted a request for a picture in a thread called 'Lockheed servo' and Mike supplied the full fitting instructions.....
lotus-suspension-f42/lockheed-servo-t29072.html
basically the body needs to be between 25 and 45 deg 'tilt' backwards and the valve rotated approx. 30deg from horizontal (see fig 3)
I'm hoping this will solve my problems....hope it help you too
cheers
G

[englishmaninwales]

Thanks for the responses, confirms what I thought. I shall try it without the servo in the circuit. I did wonder about the need for a servo in such a light car. If necessary, as suggested, I shall try some different pad specification.
Malcolm

[john.p.clegg]

Check out the search....it's a return spring in the servo...

John

Edit

Try

http://www.classicbrake.co.uk/

[Spyder fan]

Definitely the servo sticking on.
The girling remote servos are hideously expensive to replace, but a Lockheed type can be used and bought for less than ?80 on Ebay and elsewhere. Girling service kits are around ?50 including post.

If originality is not important, just remove the servo and run without it. With greenstuff or similar pads you won't notice any extra pedal effort.

[mikec2126]

Hi Malcolm
If its a Lockheed Servo - I would put money on the problem arising from the 'reaction piston' sticking - small bullet looking thingy here - http://www.triumph-spitfire.nl/servoimages.htm

Clean and red rubber grease it!

Thanks for the responses, confirms what I thought. I shall try it without the servo in the circuit. I did wonder about the need for a servo in such a light car. If necessary, as suggested, I shall try some different pad specification.
Malcolm

[Pistacchio sprint 72]

In the workshop manual, they advice its replacement every three years and recommend strongly not to dissassembly it.

I ordered a new one from Steve at sjsportscars ref SJ036J0016

[theelanman]

In the workshop manual, they advice its replacement every three years and recommend strongly not to dissassembly it.

really

a new servo every three years.......

[AHM]

In the workshop manual, they advice its replacement every three years and recommend strongly not to dissassembly it.

While Girling sold rebuild kits with illustrated instructions .

[Pistacchio sprint 72]

I guess programmed obsolescence existed already...