Lotus Elan

Bleeding Inline Booster tips

PostPost by: au-yt » Wed Aug 13, 2014 8:45 am

Hi All
I have been having fun (read frustration) bleeding brakes with an inline Girling booster.
The guys that overhauled the booster gave me some tips and I kind of respect their comments as they have both been at the brake and clutch game for umteen years....
Its important to have the piston section of the booster higher than the diaphragm end when ever you bleed brakes.
Often the case bleeding brakes one end/side is jacked up so its important to ensure that the booster is in the correct position.

Also another interesting comment they made was that they found that just bleeding the booster and the line connections was enough and they didn't need to bleed all the brakes! I think this would depend on the plumbing arrangement the Elan lines give me the the impression that the line from the master cylinder would be OK but not the pressure out line.

Next tip and I am yet to check this, was put a block of wood behind the brake pedal so you don't compress it all the way down, reason the piston goes past the supply port and sucks air...

Who knows there may be something in this.
Graeme
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Caterham 7 TC
66 one-off 2.6Ltr v8 Mid-engine Berlinetta Coupe........... in restoration
..................................................Age doesn't matter unless you are a cheese................................................
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PostPost by: Panda » Thu Aug 14, 2014 11:29 am

Hi Graeme, I'm in Balgowlah, Sydney too. Give me a ring and I can talk you through the procedure of bleeding brakes. It's not rocket science, and Elans usually aren't a problem. I'm at 0409 914455
Alan Pate
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PostPost by: robertverhey » Thu Aug 14, 2014 11:32 am

The first point makes sense to me

The way the booster is mounted places the end as the highest point.

but the other two assertions seem just plain.....wrong!

I'm bleeding mine tomorrow, now that the pedal box is finally in. Will let you know how I go. I have speed bleeders, though
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PostPost by: rgh0 » Thu Aug 14, 2014 12:48 pm

For the second point I guess if you just are replacing the booster or master cylinder you could bleed the system just to the booster outlet if you where careful not to loose fluid from downstream system. But normally if I have worked on the brake system and I am bleeding the system I want to change out all the fluid and thus it is sensible to bleed the whole system.

The reservoir port is at the end of the master cylinder and is closed of by a spring loaded valve arrangement. It closes immediately you start pushing the pedal and opens again once the pedal is back near the top of its travel.
When it opens on the upstroke is to some degree controlled by the fluid damping in the chamber that the spring loaded valve piston rod is located in at the end of the master cylinder piston as its filled with brake fluid. If you lift off quickly it will open earlier in the upstroke than if you lift off slowly.

Limiting the pedal travel would limit the amount of suck back as the pedal comes up but also limits the amount of air pushed out in the first place. if you use speed bleeders or close of the valve before the up stroke of the pedal you stop any air being sucked in regardless of the travel on the pedal you use.

cheers
Rohan
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