Brake bleeding

[whitesnake]

Hi everyone, I have just replaced my brake servo and servo cylinder because I had a problem with fluid transferring from rear reservoir to front ( not a great amount but worrying )on trying to bleed the brakes with the Gunson hydraulic kit I could only get pressure through to the rear brakes. On trying to bleed the fronts nothing appeared to happen so I resorted to the traditional method of pumping master cylinder hold pedal and release bleed valve, this did work after a lot of pumping and I now have brakes but my question is why does the pressure from the Gunson kit not blow through on the front brakes ? Can it be something to do with the reaction valve or a seal sticking somewhere? I have double checked all my pipe and hose connections on the system so am fairly confident it is not that and pumping the master cylinder did eventually bleed it but it is a mystery. Has anyone else experienced this phenomena?
This is on a series 2 OTS 4.2 RHD
Steve.

[abowie]

Did you pressurise both reservoirs?

The reservoir on the firewall that goes to the master cylinder only supplies fluid to the rears. The one mounted on the blanking plate above the passenger foot well supplies fluid to the front.

[whitesnake]

Hi Andrew, Yes I pressurised each reservoir individually to 30psi and only had a positive bleed on the rear brake reservoir, on the front reservoir nothing so I resorted to pumping the master cylinder which did eventually work. Very strange. Also my reservoirs appear reversed, master cylinder res goes to front brakes, this apparently is not a problem.

[mgcjag]

Just for info the front and rear brake connections on the servo were reversed at some time...think for S2 but you would need to check from which chassis number the change was made....Both diagrams are in the Service manual..Steve

[abowie]

Early 4.2 cars were the other way around, as you say.

I guess that maybe piston position etc might be an issue with bleeding. I have had a booster which didn't actually have a hole drilled in it: http://www.projectetype.com/index.php/t ... -much.html

As long as you have a good pedal sounds like it's all good now.

[mgcjag]

Lots of info on Jag Lovers re pressure bleeding and what can go wrong and how fluid transfer can happen...this is just one of many threads..Steve https://forums.jag-lovers.com/t/e-type- ... ding/90246

[whitesnake]

Thanks for your thoughts Gents,
it still remains a mystery but as I have a good pedal and have replaced both master and servo cylinders I am fairly confidant all is well. I shall keep a keen eye on it especially the reservoirs to see if it has cured the fluid transfer problem which was why I began this procedure.
I know previously bleeding the brakes has been a slow messy process, not my most enjoyable job but thankfully I have a result.
Steve.

[johnetype]

30 psi

I'm amazed a reservoir didn't rupture and pebble dash your paintwork with brake fluid.

Note to all, when using a pressure bleeder 5 psi is usually sufficient and I'd consider 10 psi the maximum.

[mgcjag]

Far better to use vacume to suck the fluid through rather than pressure......iv heard some bad stories of fluid going everywhere with the pressure kits......haveing said that iv never failed to bleed E type brakes with anything other than just the simple method of opening a bleed valve pushing down the pedal and tightening the nipple at the end of every downstroke and only opening it again at the top of the stroke and just repeat....Steve