540iA - 'Vague' Brake Pedal

[RSK540iA]

Hi All,

I recently bought a '96 540iA. The brakes, although stopping perfectly, don't have that definite bite as soon as one touches the pedal. One has to push the pedal down at least 10 - 15 mm before the brakes start working. I was thinking that this might be due to faulty M/C seals, i.e. the pressure by-passes the primary seals until the secondary piston takes over. Could this be?

Thanks for any advice received.

Ralf

[BillionPa]

sounds like they need bleeding.

you may also want to buy some steel hose brake lines to enhance the bite.

[DanDombrowski]

I just spent a whole lotta time in the last month working on brakes on a handful of different cars, and I fought that symptom for a bit in my Volvo, so I'll throw out some things to look out for.

First thing to check is to see if its really in the brake or in your head. Some people will drive my 330Ci and say the brakes are soft, then get into my Volvo and say that the brakes are hard, when I think the opposite. Do you drive a handful of cars on a regular basis that you could compare, or just one?

I doubt its from faulty MC seals. You will usually get a LOT of pedal travel when you have one set of seals failing. Also, you say that the car stops fine, so Im going to guess this is a no.

My guess would be either air in the lines or a mis-adjusted MC pushrod. Have the brakes always been like this, or just recently?

My advice would be to bleed the brakes and see if it improves, and mabye have a few more people drive it to see if they feel that the brake is acceptable or not.

[bmw540]

Your brake 'Bomb' needs replacing.

[RSK540iA]

You're probably right. I realize the system is hydraulically assisted (like the old Citroens). Can't the sphere be regassed? My '85 Peugeot 505 GTi brakes better than my 540i.

In my youth I worked as an AA technician for a year, testing and driving an average of 5 cars per day. I also qualified as a Jaguar technician in '86 (this explains my lacking BMW experience ). It's probably the sphere ... any idea on cost?

[RSK540iA]

Hi Dan,

'BMW540' mentioned the 'sphere'. The brakes aren't soft as such, there just doesn't seem to be the right amount of boost for a car of this caliber. Have you had this problem before on a 540i? I bought the car in April and the brakes have been like this since. I live in a mountainous area and, quite honestly, my '85 Peugeot 505 GTi is currently more reassuring down the hills.

[Bill R.]

brake bomb or sphere. Pedal effort goes up greatly when the sphere is bad

Hi Dan,

'BMW540' mentioned the 'sphere'. The brakes aren't soft as such, there just doesn't seem to be the right amount of boost for a car of this caliber. Have you had this problem before on a 540i? I bought the car in April and the brakes have been like this since. I live in a mountainous area and, quite honestly, my '85 Peugeot 505 GTi is currently more reassuring down the hills.

[DanDombrowski]

When you said that the pedal traveled 10 mm, I thought you were saying the brakes were soft. If the brake booster is bad, yeah, the pedal will be pretty hard.

[Alexlind123]

Do all e34s have brake bombs?

[Bill R.]

No

Do all e34s have brake bombs?