+2 new servo problem

[checkrail]

Hi, I swapped my Lockheed servo over for a look-a-like one from MGB Hive, it came as a complete kit, very pleased with it.The instructions on bleeding it by 'cracking open' the outlet pipe with the pedal depressed several times worked a treat ------ air hissing out giving a really firm pedal
When I checked the brake pipe connections the inlet one was weeping slightly it had a small split on thr flare so I fitted a new pipe and connections
The problem I now have is the brake pedal is now spongey with too much travel, I've gone round and bled the brakes with no sign of any bubbles. Cracking open the servo outlet now makes no difference.

Any help would be really appreciated Thanks John.

[alanr]

John,
Spongy brake pedal is air in the system.
You need to completely bleed the whole car brake system again.

Alan.

[Robbie693]

Hello John,

I have just been bleeding my brakes after fitting new calipers, it can be tricky to get a firm pedal. There are a few things you can do to improve matters.

I used a Gunson Easy Bleed as a pressure bleeder, no fluid in the Gunson bottle, just a very low pressure of around 10psi.

Start at the wheel furthest away (N/S rear if RHD) and go around a couple of times bleeding each caliper.

Disconnect the servo from it's mountings and angle the servo so that the outlet is vertical and bleed again.

Whilst bleeding tap the calipers and pipes with a bit of wood/screwdriver handle as this sometimes releases air.

When done wedge the pedal down with a piece of wood between pedal and seat and leave overnight. Air will percolate out of the master cylinder and the fluid level will drop a bit.

If any sponginess is still present, go for a short drive if safe and re-bleed.

With a bit of luck you should then have a firm pedal.

Good luck

Robbie

[checkrail]

HI Robbie, thanks very much for all your suggestions, wedgeing the pedal down over night has worked, a firm pedal with very little travel

cheers John

[Robbie693]

Result!

Great John, glad to be of some help

Robbie

[Foxie]

I have just been bleeding my brakes after fitting new calipers, it can be tricky to get a firm pedal. There are a few things you can do to improve matters.

I used a Gunson Easy Bleed as a pressure bleeder, no fluid in the Gunson bottle, just a very low pressure of around 10psi.
<snip>
When done wedge the pedal down with a piece of wood between pedal and seat and leave overnight. Air will percolate out of the master cylinder and the fluid level will drop a bit.

Robbie

Hi Robbie,

I've been down that road a good few times. That's a good tip using an empty Gunson Eezibleeder. When you get a good seal the Gunson really works, but I gave up the last time it again sprayed brake fluid all over the place through leaking caps.

I now have bleed nipples on the outlet of the master cylinder and the servo.

I don't understand the bit about air "percolating" out of the master cylinder, how does this happen ?

Cheers !

[Robbie693]

Hello Sean,

I don't know for sure but it has been discussed on here a while ago, something to do with small air bubbles migrating slowly past the seals when under pressure from having the pedal wedged down.

Either way it seems to work. Also good for bleeding the clutch. It must be doing something as the fluid level drops a bit...

Same problems for me with the Gunson spraying fluid around randomly - gives me the willies every time I use it. Much easier on the nerves using it empty!

Robbie

[alanr]

An old fashioned milk bottle half filled with fluid and a length of tube that fits tightly on the nipple plus a suitable size ring spanner(7/16ths A/F in this case) is all I have ever used all my life for any brake or clutch bleeding. I have never had much of a problem bleeding anything using just this simple equipment.

Only once many years ago on a big Citroen SM, of which the brake system was a whole different ball game, have I had brake bleeding problem which required a different pressure bleed technique.

Alan.

[Foxie]

Hello Sean,

I don't know for sure but it has been discussed on here a while ago, something to do with small air bubbles migrating slowly past the seals when under pressure from having the pedal wedged down.

Either way it seems to work. Also good for bleeding the clutch. It must be doing something as the fluid level drops a bit...

Robbie

Thanks for that Robbie, bit of a mystery, but no reason for not giving it a go !

[The Veg]

An old fashioned milk bottle half filled with fluid and a length of tube that fits tightly on the nipple plus a suitable size ring spanner(7/16ths A/F in this case) is all I have ever used all my life for any brake or clutch bleeding. I have never had much of a problem bleeding anything using just this simple equipment.

Same method my dad taught me. As long as the lower end of the tube stays submerged no air can be drawn-in on the pedal's upstroke.