Just had a specialist brake place change all 4 rubber brake hoses on my 1994 940 (Brakes are Girling front / ATE rear, Bosch ABS). I supplied the hoses (sourced from FCP Groton, made in Germany) No other brake work was done, just the hoses and a fluid change/bleed.

I collected the car and brakes worked fine, foolishly I did not look under the bonnet before driving off - trusting that as "brake repair professionals" they had done the right thing. Big mistake !

Had a look the next morning and found fluid leaking out of the top of the brake reservoir. The reservoir was completely full, right past the max level and up to the top of the filler cap, with fluid leaking out the little hole in the cap. A bit of fluid had leaked out and dripped down the master cylinder and over things, so I had a bit of cleaning up to do under the bonnet in the vicinity of the master cylinder. I used a syringe (a large bore one without a needle, not the junkie kind !) to suck out the excess brake fluid from the reservoir and bring things back to the max level. 12 hours later things seem stable at the max level.

My question is "how could this happen ?" !! Surely a brake place would not deliberately overfill the reservoir so excessively ?

Could there be some cause for this phenomonen, apart from gross incompetence on the part of the staff at the brake place ?

I wonder how much thermal expansion would occur if say the reservoir was filled with very cold brake fluid to the max level, and then things heated up. Could that lead to an overflow ?

Is there some other characteristic of the system that results in it being possible to overfill the brake system, such that when things adjust back to the "normal" state, the system has too much fluid ? Does it matter if the handbrake is on or off when the brake system is filled with fluid ? Could my new hoses be doing some bizzare shrinking behaviour ??!! ABS wierdness ?

I'm going to ring the brake place on Monday and complain, but it would be nice to get some feedback / suggestions before I do this...

John Marshall
Christchurch NZ
1994 940GL 162,000km