11 replies to this topic

[ianclark1275]

hello,

after much searching and a few good pointers that i have tried im still no further forward

I replaced the Yellow tag twin master in about 2003 from minispares

it took ages to bleed but eventually came good and passed a number of MOTs.

rear cylinder failed and all fluid leaked out (over winter 2011)

now the problem has returned

no fluid comes out of the lower hole when pipe is not fitted

no fluid comes out of the hole with a 30psi eezi bleed on reservoir

if you wait 2 mins then a small amount comes out after stamping on the pedal

put finger over hole and press - feel pressure - release - feel suction.

took off and inspected and poured fluid in through holes then reassembled - no difference

put air line on the lower outlet and nothing happens - no bubbles in the reservoir even when pressing pedal.

suspect somethings stuck in the bottom of the reservoir, remove and clean is next...

or there is a problem with the drillings / plunger travel?

any similar problems? i thought that 30 psi ezibleed and pipe disconnected would do something!!!

thanks

IC

[100ev8]

sounds like a master cyl problem but slacken the master cyl off about 3 threads each nut . will it bleed then ? is/was the pedal right at the very very top when brakes were ok ?

[tiger99]

I strongly suspect that your pedal has no freetravel, so the master cylinder piston is not retracting far enough to uncover the reservoir port. You may need a shim under the master cylinder, but first check the heavy, and very important, pedal return spring, and look for signs of the pedal being obstructed in some way, for example by the carpet, or an improperly adjusted stop light switch, if it is the adjustable type.

Edit: Near simultaneous post, and we are thinking along the same lines. Loosening the nuts is indeed a quick check. Lever the master cylinder up slightly with a screwdriver, with the nuts loosened, if necessary.

Edited by tiger99, 03 February 2013 - 11:55 PM.

[ianclark1275]

Ahh...

i can see the theory

i can feel a metallic knock when the pedal is right at the end of travel, and thats where the only braking that's left is
i did a track day at blyton and was close to anglia i was that far off the track on the corners


Im using a bolt and Nyloc nut instead of the pin and clip and no carpets but will look at the travel..

thanks

IC

[100ev8]

bolt and nut wont effect the travel really but you need to try the above.and or remove nuts all the way and try pressure bleed again . any fluid from the bottom port now ?

[ianclark1275]

i will have a go tomorrow thanks guys

[colinu]

Maybe hijacking this post (sorry)... but should a master tandem be bench bled in a horizontal position before fitting it to the bulkhead?

[tiger99]

Good question, but no, there is no advantage in bench bleeding, horizontally. But some people claim that bleeding is easier, on any Mini, and perhaps other cars, if you loosen the pipe(s) at the master cylinder and bleed, using an Eezibleed if possible, until fluid is emerging, then tighten them up.

[colinu]

Thanks for the advice tiger99 - it'll save me some unnecessary hassle when I refit mine later this week.

[ianclark1275]

right.

i loosened off the Master cylnder bolts to the bulk head and got the 4yr old to press the pedal a few times, bottom pipe completely removed from the cylinder.

press down---air pressure felt
lift off - vacum felt

the vacum bit is not right, surely this must "pull" the fluid back from the reservoir - not hold the vacum


cylinder off and reservoir off.

air line in the lower "fluid in" port - nothing - not good.

air line in the upper "fluid in" port - air out of the "upper outlet" - good.


circlip off and inspect rubber on lower piston - all ok.

refitted and as i pushed it up it expanded out of the side of the drilling and ripped.

game over.



going back to minispares to get some rubbers and will ask the guys there..

[ianclark1275]

This look similar to the Yellow tag item

there is no path from the small inlet hole to the top of the rubber i belive

the rubbers must have increased slightly over time or the original clearance (determined by the washer at the base of the unit held in by the circlip) was tight to start with

im going to replace rubbers and replace the thick washer (19) with a thinner one.

IC

[ianclark1275]

BRAKES NOW WORKING

i bought GRK1035 Repair kit and rebuilt and all is fine...

Cause looks like the rubber seals had swelled and moved far past the smaller hole in the Cylinder

the cause is most likely the small matter of me adding Power steering fluid into the master cylinder when i run out of fluid a number of months ago

anyway the new seals are fine and Ezibleed fired up through all 4 corners, pedal came back, still a bit spongy but its fine for now.


you can see why i was struggling.......