Brakes

[Niels Jonassen]

Some time ago the issue of brakes was discussed, and it appeared that quite a few Aurelia owners did not know that the plunger in the brake reservoir is supposed to be up - and to stay up. Now I have looked at an internet page with 11 adverts for Aurelia, 8 B20's, 2 B24's and 1 B10. There were photos of the engine compartments of them all. On 3 photos I could not see the reservoir. On the remaining - all B20's - only one had the plunger up. They were all advertised by dealers who asked a lot of money for the cars.

[lancialulu]

My newly acquired B12 had been sitting around at a dealer for some months when we decided to drive it home. The brakes worked fine on the test drive but on closer examination the plunger was down. I pulled it up and it stayed up but part way home I noticed brake fluid at the rear of the car and the plunger had dropped. I topped up the reservoir (it was half full) and pulled the plunger up the top, and it stayed up for the rest of the journey. The rear cylinders luckily had resealed them selves. Chris Gawne had warned me of this issue so I had bought a large bottle of dot4 for the journey home. It seems my car had new brakes all round. I wonder if those B20s have some expense waiting in the braking department.....

[Dikappa]

The plunger going down is also often caused by the cylinderwall,no return valve or seal in the reservoir itself, which seems often to be neglected in a brake system rebuilt.
So with plunger down and no signs of brake fluid, best check the reservoir...

[Brian Long]

The Aurelia braking system relies on the pressure generated in the system by the spring-loaded plunger in the brake fluid reservoir to keep the cups in the master and slave cylinders in firm contact with their respective cylinder walls.
Other braking systems using slave cylinders achieved this by having a small spring-loaded valve in the master cylinder which maintained a slight positive pressure in the system when the brakes were released.
Previous contributors are right in saying that the plunger should always be up. A slow loss of plunger height means either leakage past master or slave cylinder cups or, hopefully, only past the cup in the fluid reservoir.
My B12's plunger remains in the up position indefinitely but I still check it during any extended periods of inactivity.