Servo

[Robbie693]

I seem to have nothing but questions lately....

This 'spring in the air valve fix' for the Lockheed servo; can anyone tell me the size/spring rate or just a decription of what I would need?

I was thinking maybe I could make one from a bulb or battery holder from a torch or something...?

Alternatively, I've read that removing one of the seals in the air valve fixes it; which one do I remove - the upper or lower?

Cheers

Robbie

[theelanman]

John Clegg is your man.....
on here as jctx ????? something IIRC
no doubt he'll spot this and point you in the right direction
cheers
Gareth

[Robbie693]

Cheers Gareth,

I emailed John but he hasn't replied yet, in the meantime I got this from Lockheed:

... the problem is most likely the hydraulic reaction valve sticking open thus holding the air valve open. The easy way to test this; is to create the problem then disconnect the vacuum hose, the brakes should then come off.

To rectify; remove the air valve (take care when removing the cap as there is a spring inside) by removing the 5 screws, remove all the components then remove the three screws holding the air valve body to the cylinder. This exposes the reaction valve No. 35A in servo drawing (this is where you might find two small seals) to remove the valve you may need to press the brake pedal to hydraulic it out (take care as fluid may spray); clean both the piston and bore (it may be prudent to remove the lower seal if fitted) refit using a special silicon grease (send me your address and I will put a sample in the post) re-assemble in reverse order.

Fitting a stronger spring in the air valve will only delay the reaction valve making the braking unpredictable.

Change your brake fluid using DOT3 fluid, and change your fluid at least aver 2 years, preferable ever year (Brake fluid is hygroscopic; absorbs moisture) do not use silicon brake fluid (DOT5) as this is 2 ? times the viscosity of normal brake fluid and may cause a similar problem.

The position of the servo is only necessary for bleed purposes, the air valve needs to be in the seven o?clock position and the outlet port above the inlet port approx. 30 degrees.

I'll give this a go first

[john.p.clegg]

Sorry,but I've been in Italy for the past week but am on the case now
John

[types26/36]

John, Here is a couple of pics of a Lockheed servo, is the spring fitted under the air valve to force it on to its seat (black rubber ring) and as asked by another poster can you give us some diamensions.....even a pic?
Thanks Brian

[simonriley11]

I have the lockheed servo fitted (by the PO) and I've started to notice that the brakes stick on slightly after I've applied them. I am using silicone fluid so if I change to non silicone how can I make sure I don't contaminate the new fluid with silicone.

[john.p.clegg]

Here are a couple of photos to help (if i can download them)
John

[john.p.clegg]

O.K. so i'm no good at posting piccies,it fits on top of the rubber diaphragm to help it back down,under the plastic cap
John
P.S.
I've got piccies just having problems posting them.......

[john.p.clegg]

Robbie

You will have the spring shortly and you've the lockheed printout,do you have the technology to post photos of both?
Thanks
John

[Robbie693]

Sorry, don't have a digi camera so can't take a photo of the spring unfortunately.

Here's the diagrams of the servo though:





John, if you have a photo, you could mail it to me me and I'll put it up tomorrow if you like.

[types26/36]

Here are Johns pics of the spring/servo modification

[types26/36]

I am using silicone fluid so if I change to non silicone how can I make sure I don't contaminate the new fluid with silicone.

I think the only "sure" way would be compleatly strip the system and clean every part but I changed from silicon to normal fluid on my Seven (no servo) just by bleeding the system several times, it is about 15 years since I did it and it has given no problems.