oh no servo...

[Elanconvert]

hi all haven't posted for a while [been busy with the elite..]
anyway little problem with brakes locking on......wasn't sure if it was m/c or servo - calipers just redone so not them........noticed that they freed themselves after a few hours, so decided on elimination process....
left the car overnight and sure enough wheels were free in the morning.
started her up and wheels immediately locked [hadn't touched the brake pedal] so obviously a servo fault, but what specifically? could it be a simple fix? a bit specialist I fear....
should I not bother my little head with it and just send it off for recon?
disconnected the vacuum pipe, and will run without servo for now.......

any advice appreciated!

fred

[Bigbaldybloke]

You don?t say if it?s a Girling or Lockheed servo. I rebuilt my Girling one years ago and it was not too challenging and worked well till I took the car off the road for a chassis replacement. It?s not been back on the road since, but that?s nothing to do with my servo rebuilding abilities!

[Foxie]

I had this problem a long time ago.

It turned out that the master cylinder pushrod was not allowing the piston to retract fully and allow the small seal at the end to open and release the hydraulic pressure. I had of course fitted and adjustable pushrod and removed all clearances.

Same problem could be cause by a stiff pedal pivot bush, or weak pedal return spring.

[Davidb]

I had the same experience as above. Check the adjustment of the brake pedal push rod-whether you touched it or not during the rebuild-would be my advice.

[john.p.clegg]

Could also be the lack of the later mod of a spring in the air-valve...

a tap on the brake pedal should free it .

John

[pauljones]

What would it be like without the servo conected?

Cant be bad can it? Hope not as ill be disconecting mine.

[Bigbaldybloke]

If you are planning to run without the servo it would be better to bypass it on the hydraulic side as well as disconnecting the vacuum. That way you could remove it and overhaul it at your leisure. The brake pedal will require a hefty push, but some prefer it that way as they say it gives more feel. Me being a 6 ft plus, 16 stone weed, prefer having the servo in use!

[Elanconvert]

thanks for all the replies/advice.....

have bypassed the servo and removed the offending article......decided that if I can rebuild engines and master/slave cylinders, I might be able to tackle the servo......unless special tools/skills are required ...[btw girling i forgot to say].....

as bigbaldybloke says....now it's on the bench, I can tinker at my leisure [leisure? what's that? oh yes golf time....hang on, that doesn't work].....if the worst comes, I can always send it off to a specialist after I have b*****ed it...

I see that seal and gasket kits are available .........any suggestions as to supplier? or more importantly, any to avoid??!!

fred

[69S4]

if the worst comes, I can always send it off to a specialist after I have b*****ed it...

You're a braver man than me doing that!

[Davidb]

I have a 0.70" bore tandem master cylinder in my Elan and love it! The pedal pressure is perfect and no stupid servo to take up room or fail.

[jeff jackson]

I had the same experience as above. Check the adjustment of the brake pedal push rod-whether you touched it or not during the rebuild-would be my advice.

What is the adjustment? Is there a measurment for this, and how do you measure it?
Regards
Jeff

[Foxie]

I had the same experience as above. Check the adjustment of the brake pedal push rod-whether you touched it or not during the rebuild-would be my advice.

What is the adjustment? Is there a measurment for this, and how do you measure it?
Regards
Jeff

The original pushrods are fixed length, so there is a small amount of lost motion before the piston moves forward. This can be minimised be using an adjustable rod, which can be extended by screwing out from a threaded clevis pin to reduce free play. If it is screwed out too much, the piston will not fully retract, and the hydraulic pressure will not be released. The optimum setting is a matter of trial and error. An option for solid pushrods is to shim out the master cylinder brake box mounting.

[Davidb]

Thank you Foxie. It was not on an Elan that I had the problem but the same set-up with adjustable push rod. You must have some free-play after releasing the brakes or the push rod is too long.

[Donels]

I have just rebuilt my Girling Servo and if you can rebuild master cylinders you can rebuild a servo. I got the parts from Northwest Classics and they are excellent, giving plenty of useful advice.

The P.O. said it had suffered complete brake failure and I found a torn seal in the servo, which would explain it. I too had problems fitting this seal but Peter at Northwest offered to install the piston FOC. Now reassembled and ready to refit, so I cannot tell you it works but everything that came out went back in fully refurbished.

Dave

[Bigbaldybloke]

I rebuilt mine years ago and the trick is to make the special assembly tool, which is a bit of coat hanger wire bent to a shape given in the instructions. It?s still in one of my toolboxes to this day. But as said above, if you can rebuild a master cylinder, you can do a servo!