440 Li brakes

[Alanandkima]

Suddenly lost almost all braking! I found the back cylinders were leaking so changed them. After that bled the brakes and seemed to have a firm pedal but when I turned on the engine the pedal went to the floor. I changed the master cylinder seals, but its just the same. Engine off, firm pedal - engine on, goes to the floor. Any ideas anyone?

[Paul240480]

Hi, you said that you've bled the brakes. Have you replaced the fluid alltogether?

If not try that, as over time the fluid will break down & water gets in somehow. This induces brake-fade and 'pedal to the floor syndrome'. Others I'm sure will expand on the technicalities............... Good Luck.

[Alanandkima]

Thanks for the reply. Yes, I've changed the fluid and bled the system several times. There's no leak anywhere and no fluid loss, just no pedal when the engine's running. I wondered about a servo fault, but surely a failed servo would leave me with a pedal, but just a very heavy one?

[NI_Volvo_Nut]

Sounds to me like the m/cyl is done, replacing seals usually wont cure the problem, try 2nd hand one, if this cures the problem i'd look for a new one then.

[jlgrosvenor]

I have recently overhauled the master cylinder on the B18U engine car.

I found it very difficult to get the clip out of the top of the master cylinder. It is kind of like a circlip, but without any holes to get hold of and compress with curclip pliers, just some slightly raised lugs instead. It took three guys all working at once to get the thing out with screwdrivers and long-nosed pliers. How did you remove the clip? I put a normal circlip back in once overhauled.

When you were replacing the internal seals of the cylinder, what was the condition of the interior surface? It should have been like new, with no scoring and no signs of corrosion. If there were any visual imperfections, a new cylinder is the way to go. I think they can be had for about £40.

The other thing to check is the seal between the vacuum booster and the master cylinder. Did you get a replacement seal in the master cylinder repair kit?