Brake Cylinder Quicky

Post by **Orkney** » Thu Aug 02, 2007 10:00 am

Finally got the front cylinders off after much aggravation, mostly with the flexi pipe unions to the copper- drivers side both siezed (no wonder it pulled to the left

) anyway manged to prize one of the siezed ones open.
Its nothing like the ones from the other side - different short piston with a little plastic airbag with spring and a rubber cup - this cant be right surely?
Anybody know what this is ?
Will try and get a pic later when hands are clean enough to pic up the camera.

Post by **alex_holden** » Thu Aug 02, 2007 10:04 am

I think the one with the plastic doohickey under the rubber cup is the genuine Lockheed type and presumably the other is a pattern.

Post by **bmcecosse** » Thu Aug 02, 2007 10:07 am

Pattern cylinders tend to have an O ring type seal (may not be exactly O in shape - but seal sits in groove in cylinder) I think rather than a cup rubber with backing spreader and spring.

Post by **Orkney** » Thu Aug 02, 2007 10:17 am

Cheers chaps, did wonder - but replacing all round with patterns had nothing to compare to. Did wonder if they wernt the wrong cylinders completely.
Out of curiosity would a pattern with that set up and a genuine have a different 'push factor' if there are different amounts of fluid being acted upon in the cylinder?
All academic of course as all being renewed (its looking good & cant wait to see the difference later on) just bugs the hell out of me when someone has replaced one side only of something important - has been done to death on the car and points to less than fastidious maintenance.

Post by **alex_holden** » Thu Aug 02, 2007 10:20 am

It's the bore diameter that governs how hard it pushes on the shoes for a given pedal pressure.

Post by **Orkney** » Thu Aug 02, 2007 10:32 am

Hmm cant remember the basics of hydraulics LOL School was a long time ago. Guess its surface area thats the factor so if both bores teh same regardless of CC in teh cylinder would be the same.
Yeah that would be right wouldnt it - otherwise as a piston was pushed it would change - you cant in teh normal world compress a liquid so it acts on teh surface area of the ram.
Bit too scientific for this time of the day

Post by **dunketh** » Thu Aug 02, 2007 5:03 pm

I've got all 'Lucas' cylinders and they work brilliantly. (Patten-style with the rubber O ring)
I left the flexi pipe attached at the car side of things and turned the cylinders to undo em.

Post by **bmcecosse** » Thu Aug 02, 2007 8:29 pm

That trick works fine - IF the thread on the new cylinder has been started in more or less the same place as the old cylinder. What you do not want is a flexi pipe twisted up like a spring!

Post by **dunketh** » Thu Aug 02, 2007 9:12 pm

Aha, one step ahead of you.
I twisted my pipe (a little) the opposite way so when I turned the new cylinder on it was actualy unravelling. Resulting in a straight un-twisted flexi pipe.

Post by **bmcecosse** » Fri Aug 03, 2007 10:03 am

Yes indeed - but the thread 'start' still needs to be in approx the same place - it's about a 50/50 chance if it will be ok.

Post by **Orkney** » Fri Aug 03, 2007 10:19 am

Bleeping flexipipes

Nearly got it finished last night, left the rear one till last and it went downhill quickly !

The welded bracket came off before the old one came undone, had to be bolted back on.
Then the copper to the master had a wonky thread and wouldnt go into the the new flexi, think it was cross threaded in teh original and wasnt prepared to risk it so replaced that.
Wasnt an issue as had to get into the master cylinder area anyway.

When i started phase 1 of the brakes, front pads, rear cylinders, new bleed nipples. After the first bleed the pedal wasnt returning. Unbeknown to me the return spring had come off.

Tried to get it back on last night but one of the hooks had been bent and the darned thing snapped so waiting for a new one now

Looks like a nasty job to fit too so not looking forward to that.

Still on the bright side whilst the floors up can give the inside of that chassis are a good cleanout and lick of underseal.

Post by **bmcecosse** » Fri Aug 03, 2007 1:08 pm

The thread on the rear axle is 3/8" bsf remember! however - I am not sure if the flexi is also BSF - or is the T threaded 2 x BSF and 1 x UNF - for the flexi?? Anyone know for sure ?

Post by **Orkney** » Fri Aug 03, 2007 1:38 pm

the rear nipple threads are different to the front ones, all 3 flexi pipes looked the same and fitted to the new copper with ease.
Will have to look at the old one as chances are it was original