BestyA Posted September 12, 2020 Report Share Posted September 12, 2020 I am beginning to think my GT6 doesn't like me - drove the car out of the garage applied the brakes and both front brakes are seized solid. I have rebuilt the brakes all around. Including rebuilt master cylinder (new seals) and rebuilt servo MK2b Girling using full seals kit. I assume it will be the servo as it is acting on the front? - any ideas / suggestions much appreciated. Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 12, 2020 Report Share Posted September 12, 2020 crack a bleed nipple to release any pressure then you know if its mechanical seize or trappped pressure first place for trapped residual pressure is has the M cyl push rod got some free rattle play, if the pedal is stiff it stops the Mcyl recoupeating and pressure buils up but cannot be released Pete Link to comment Share on other sites More sharing options...
johny Posted September 12, 2020 Report Share Posted September 12, 2020 Could also be a problem with the air valve on the servo not shutting off the admission of air to one side of the diaphragm so the vacuum is continually applying pressure to the hydraulics. If the brakes are released (once any residual vac has dispersed) when the engine isnt running it would confirm this.... Link to comment Share on other sites More sharing options...
BestyA Posted September 12, 2020 Author Report Share Posted September 12, 2020 Thanks, I opened the bleed nipple on front brakes, it released the pressure and freed up the brakes, I think I could hear the servo ease off. So at least I have been able to roll the car back into the garage! The thing is it was only the fronts - I jacked each corner of the car up to check the rears were free. So question I need to figure out - is it servo or master cylinder? Link to comment Share on other sites More sharing options...
BestyA Posted September 12, 2020 Author Report Share Posted September 12, 2020 1 minute ago, johny said: Could also be a problem with the air valve on the servo not shutting off the admission of air to one side of the diaphragm so the vacuum is continually applying pressure to the hydraulics. If the brakes are released (once any residual vac has dispersed) when the engine isnt running it would confirm this.... Thanks for your reply, I tried taking off the vacuum tube but no effect. The car sat on the drive for an hour with the engine off but brakes stayed seized. Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 12, 2020 Report Share Posted September 12, 2020 we dont deal with chick or egg , i would check the pedal is fully returning as a cheap fix then attack the servo and its air valves pete Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 12, 2020 Report Share Posted September 12, 2020 can you check the air valve normall behing the inlet air filter , is free , its a small piston with a light spring to return it if its stuck youmcan get what johny says which servo is fitted orig or aftermarket ??? Pete Link to comment Share on other sites More sharing options...
BestyA Posted September 12, 2020 Author Report Share Posted September 12, 2020 3 minutes ago, Pete Lewis said: can you check the air valve normall behing the inlet air filter , is free , its a small piston with a light spring to return it if its stuck youmcan get what johny says which servo is fitted orig or aftermarket ??? Pete 2 minutes ago, Pete Lewis said: can you check the air valve normall behing the inlet air filter , is free , its a small piston with a light spring to return it if its stuck youmcan get what johny says which servo is fitted orig or aftermarket ??? Pete I will take the servo off and check. Hopefully that's it, otherwise I will take all apart and check all seals are in and the right way around. It's an original Girling 2B Link to comment Share on other sites More sharing options...
johny Posted September 12, 2020 Report Share Posted September 12, 2020 strange to be a servo problem if theres no vacuum to provide the force... However its difficult to be sure that the vacuum has dissipated even after an hour as maybe your non return valve and system is really airtight? Link to comment Share on other sites More sharing options...
BestyA Posted September 12, 2020 Author Report Share Posted September 12, 2020 9 minutes ago, johny said: strange to be a servo problem if theres no vacuum to provide the force... However its difficult to be sure that the vacuum has dissipated even after an hour as maybe your non return valve and system is really airtight? I will start it up and see if they lock on again, then see if I can figure out if there is a vacuum there Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 12, 2020 Report Share Posted September 12, 2020 to release any vacuum you can prise the plastic elbow/valve out of its grommet in the canister and realse vacuum from the canister. have you checked the pedal for free play ??? very imprtant ....and cheap fix Pete Link to comment Share on other sites More sharing options...
BestyA Posted September 12, 2020 Author Report Share Posted September 12, 2020 6 minutes ago, Pete Lewis said: to release any vacuum you can prise the plastic elbow/valve out of its grommet in the canister and realse vacuum from the canister. have you checked the pedal for free play ??? very imprtant ....and cheap fix Pete No free play in the pedal, I will prise out the elbow and see what happens. Link to comment Share on other sites More sharing options...
dougbgt6 Posted September 12, 2020 Report Share Posted September 12, 2020 I had this with my new servo (Lockheed), foot on the brake and locked up. After 1/2 hour brakes relaxed a bit but binding, until I pressed the pedal again! Turned out servo had been poorly assembled, one of the internal airways was blocked with grease and the air valve was entirely inadequate. Cleaned up the innards and put an external one way valve on the vacuum pipe. Shiny chrome Jaguar one, nice! Doug Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 12, 2020 Report Share Posted September 12, 2020 pedal pivots do seize , stops full return of the pedal , you need to lift the baukhead gaitor and check with foot off there is no pressure acting between pedal clevis and the push rod into the end of the cyl it must have a small amount of free wiggle if no play its either seized pedal or brake switch or pedal stop needs adjusment Pete Link to comment Share on other sites More sharing options...
johny Posted September 12, 2020 Report Share Posted September 12, 2020 Surely back brakes would be affected as well although maybe with the servo not as much as the fronts? Link to comment Share on other sites More sharing options...
BestyA Posted September 12, 2020 Author Report Share Posted September 12, 2020 Thanks everyone, looks like it is coming out for a bit of investigation. Link to comment Share on other sites More sharing options...
dougbgt6 Posted September 12, 2020 Report Share Posted September 12, 2020 GT6 servo only works on the front, so if only the front are locking up, it's the servo! Doug Link to comment Share on other sites More sharing options...
dougbgt6 Posted September 12, 2020 Report Share Posted September 12, 2020 28 minutes ago, johny said: Surely back brakes would be affected as well although maybe with the servo not as much as the fronts? GT6 servo only works on the front, so if only the front are locking up, it's the servo! Doug Link to comment Share on other sites More sharing options...
BestyA Posted September 12, 2020 Author Report Share Posted September 12, 2020 1 hour ago, dougbgt6 said: GT6 servo only works on the front, so if only the front are locking up, it's the servo! Doug That's my line of thought now Link to comment Share on other sites More sharing options...
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