Technical brakes need to be 'primed' every journey

[StoneNewt]

This is a weird problem, every time you start the car the brakes need some sort of priming. The symptoms are the brakes give no feel and give this this spongy sensation until you give them a few long hard presses of the brake peddle, even if the brakes are in this state there is no loss of power or increase in the peddle travel. The number of stabs needed to get the brakes into a communicative mood is loosely related to the amount of time the car has been switched off. Anyone have any ideas what might be causing this?

 

[Hellcat]

Water/air in brake lines? Worn seals in master cylinder? Damaged/worn flexibles?

 

[StoneNewt]

I was trying to work out what would cause a lack of feel and sponginess without lengthened travel. I should have mention I've already replaced pads, discs & brake fluid and this problem has remained the same since I got the car.

 

[Hellcat]

Could be the braiding in the flexibles deteriorating and becoming expandable? Would cause spongeness without extending the travel..

 

[faster4_tec]

air bubble thats really close to a resivoir or void in a caliper or 4

I got this on the rally volvo (see sig pic) after it got new brake pads in barnaul (central russia), took another week until the pedal was anywhere near firm, and even then it was practically in the carpet until it firmed up

bled it several times, gave up, reckon there was a bubble or a larger air void in one of the caliper (4pots up front, 1 or 2pots at rear).

car was terryifying for about 1000miles

oh and front pads were BRAND new and I fitted them about 50miles before we left!!! all I can say is big mountains+ well overladen volvo+ driver trying to destroy the car = brake pads last about 7,000miles!!

 

[StoneNewt]

Could be the braiding in the flexibles deteriorating and becoming expandable? Would cause spongeness without extending the travel..

Sane idea, I might buy some Goodridge flexies however why would it firm up after a few long hard stabs of the brakes? This is what's throwing me, the combination of symptoms seems strange to all the ideas I have.

I don't know how a worn seal in the master cylinder would effect the way the brakes work & feel.

 

[Hellcat]

I suppose if there was a very small weap past the seals in the master cylinder it could produce these symptoms. Once you're driving does it firm up and stay firm providing you use the brakes often enough?

I've had a worn master cylinder but it didn't produce enough braking force, and didn't firm up with pumping the brake.

 

[StoneNewt]

Once primed I think as long as the engine is running it doesn't get spongy again, I say this as I can't fill it up with fuel without it needing to be primed, but not experienced a laps back to spongy even after 15min on the motorway without touching the brakes.

 

[toad101]

i recently had a similar problem , one of the rear wheel cylinders needed replacing