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Lotus Elan Sprint 1970


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Can anyone advise on this.

On a few rare occaisions, although it is increasing, having applied the brakes ( I have a servo) the brakes stay on for about a second then release. once moving, the car runs freely. None of the callipers are seized having just been re-built. I guess it is either the master cylinder or the servo. Has anyone experienced this ? If I have it on blocks and try to simulate it without the engine running all wheels run freely. That hints at servo to me. Any thoughts ?



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If it didn't happen before the calipers were rebuilt I'd be a little suspicious of them but not likely if all four wheels are sticking so, as you say, it's more likely to be the servo or the MC. 

FYI when it's up on blocks just because the engine isn't running doesn't mean the servo isn't operating, you have to exhaust the vacuum in its reservoir by pressing the brake pedal several times before it stops functioning :thumbup:


John W

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  • 7 months later...

More than likely a servo issue: usually with the air admittance valve, or the small hydraulic piston that operates it located in a bleed off port from the main servo bore. The piston can rust/get sticky: the hydraulic pressure is sufficient to move the piston and open the air admittance valve, but the air admittance valve spring is not strong enough to overcome the stiction and push the piston back down immediately when the pedal is released, causing the servo to "Hang". In extreme cases the brakes drag substantially after initial pedal operation. Servo replacement is your best bet.

Regards, Phil

Edited by Phil.C
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