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NOTE when you fit the new MC, put DC111 on the metal inlet ports of the MC then smear it on the grommets , and on the booster to MC square seal as well.
NOTE water runs down the tank and weeps into the feed ports of the MC as can be evidenced by the rusty condition of the grommet to MC body.
over time water will corrode the grommet bore and then leech into the fluid,
then it will corrode the MC bore,
then when you bleed the brakes by pressing the pedal to the floor,
the seals will get cut as the seals will be going past areas that they dont usually touch
You just put new switches into your MC and now your getting a fluid warning ,
that means you have a mismatch of fluid in the MC bore so its likely one of the MC seals has been damaged.
NOTE get a piece of weatherstrip about 6 inches long,
and put it on the ridge above the MC lid ,
this will help divert water away from the MC and reduce the water that runs down the tank.
NOW is the best time to buy a new MC as they are only 495.00 they used to be 175.00 the price will never go down
Make sure you get an ATE MC and a liter of ATE Gold fluid
NOTE in the picture you can see i have installed a strip of weather seal along the ridge above the new MC
NOTE when you fit the new MC, put DC111 on the metal inlet ports of the MC then smear it on the grommets , and on the booster to MC square seal as well.
NOTE water runs down the tank and weeps into the feed ports of the MC as can be evidenced by the rusty condition of the grommet to MC body.
over time water will corrode the grommet bore and then leech into the fluid,
then it will corrode the MC bore,
then when you bleed the brakes by pressing the pedal to the floor,
the seals will get cut as the seals will be going past areas that they dont usually touch
You just put new switches into your MC and now your getting a fluid warning ,
that means you have a mismatch of fluid in the MC bore so its likely one of the MC seals has been damaged.
NOTE get a piece of weatherstrip about 6 inches long,
and put it on the ridge above the MC lid ,
this will help divert water away from the MC and reduce the water that runs down the tank.
NOW is the best time to buy a new MC as they are only 495.00 they used to be 175.00 the price will never go down
Make sure you get an ATE MC and a liter of ATE Gold fluid
NOTE in the picture you can see i have installed a strip of weather seal along the ridge above the new MC
i am not a mechanic I bring the car to the workshop.
my mechanic has replaced the 2 switches and he replaced the brake fluid.
The car don't leak brake fluid anywhere and the brakes are good the car past the MOT brake test...I don't get it, the car brakes good.
I don't get a fluid warning,
Just a brake pres warning light . When I turn the engine off and start the warning brake pres is gone. After 3 min the warning gets back
Do you know if your mechanic used the cheaper version of the switches? I've had some of those come bad out of the box and only use the more expensive ones.
If the best switches were used and properly bled,
then the MC inner seal has failed and it doesnt mean it has totally failed,
just enough to make a mismatch of the pressures where one switch closes before the other one.
That said your MC looks old and the inlets look rusty under the grommets
Do you know if your mechanic used the cheaper version of the switches? I've had some of those come bad out of the box and only use the more expensive ones.
If the best switches were used and properly bled,
then the MC inner seal has failed and it doesnt mean it has totally failed,
just enough to make a mismatch of the pressures where one switch closes before the other one.
That said your MC looks old and the inlets look rusty under the grommets
More on things that fail: The wiring and connections at the switches are hidden inside the boots that cover the connections. Invest some time and effort in carefully removing the wire connections, and inspect the wiring going back up into the plastic sleeve that wraps the harness there.
I can't overstress the need to have good matching switches.
Stan's visual assessment of MC condition is pretty accurate. The rust around the top ports and grommets is a telltale. The good news for you is that your early series dual-diagonal master cylinder was designed to be rebuildable. Parts are scarce, and by the time one needs serious attention, it's due to corrosion rather than wear of the rubber replacement bits. I've rebuilt a few with new rubber cups and pistons, but I'm less than 100% successful with honed bores. Better and certainly more reliable is to find a new or factory-rebuilt replacement.
Know also that the system demands "bench-bleeding" the master cylinder prior to installation or as part of any service that included running the reservoir low. A little air stranded in the end of the MC will give you your symptom, and the only way to reliably purge the whole MC is with bench bleeding with the MC level as you work. The two pistons are connected hydraulically, with a thin washer check-valve on one piston. Getting the air out and keeping the positions of the two pistons correct to each other is absolutely essential, and can only be achieved with bench bleeding. ATE used to supply a hoses and connectors kit with every replacement cylinder for bench bleeding, and they did that for a reason.
04-27-2020, 09:41 AM
