Brake pedal very stiff at engine start

S

sk93

Veteran
 Nottingham
I've a habit of putting my feet on the brake and clutch when starting the car - I've done this since I nearly jumped forward into a very shiny Diablo when I had just past my test.

However, starting very recently, I'm finding that when I jump in the zed, the brake pedal is incredibly stiff, and I can't push it down far enough so that it actually engages the brakes when the engine is off.
As soon as I start the engine, it works perfectly; I've noticed no loss of pressure, no stiffness, no vibration, nothing against the norm whatsoever.
Also, when I turn the engine off, the pedal feels "normal" for this state - as in, it's got no assistance, but can be depressed etc.
It's only after leaving the car for a good few hours (say, overnight) that the problem arises.

I've checked fluid levels, and they're fine. I checked around the pipes and cylinders for signs of leaks, but didn't find any, and my fluid is due to be changed in about 8k.
I'm also positive I've not "boiled" said fluid either.

Any suggestions, or should I not be worried?
 
There's nothing wrong with them. Its perfectly normal. Switch your engine off and pump the brakes a few times, it will feel spongy and you won't be able to depress it all the way. switch the engine back on with your foot on the brake and you will feel it.

Forget about braking when starting the car, just wiggle the stick to make sure its in neutral 8)
 
SK - you have most likely got a very slight leak in the servo. During normal driving it's vacuum is constantly 'topped up'. Park up and leave it an hour or so and the pressure equalises, or as chrismann85 notes pumping the brakes a few times has a similar effect. Start the engine and hey presto - back to normal.

While nothing to worry about you may want to check the servo and vacuum hoses for leaks.
 
chrismann85, I get what you're saying, but what I was trying to convey was that when I get into the car, I could put all my weight on the pedal for the first time, and it'll travel about 3cm before stopping - and I'm not the lightest fairy in the woods ;)
Beforehand, if I did that, it'd sink to the floor on the first "pump". Each depress after that would increase the pressure, and by the fifth/sixth depression, it'd be as stiff as it is now on the first.

I think I'm just paranoid that it's an early warning of a far more serious problem :)


CJ - I did a quick visual check of the hoses and the servo, but didn't find anything obvious.
Perhaps a more detailed look is in order :thumbsdown:
 
SK93 what you describe is a classic situation where the residual vacuum stays in the servo. Get in an hour later and pump the brakes and each time the pedal will move less and feel harder as the vacuum is used up (also exaggerated by the system becoming pressured, pads tight on rotors, etc.)

When you get a minor leak after seconds to hours, depending upon the severity, the pressure will be lost and on first pressing the pedal it will feel rock hard.

The chances of finding the leak are slim as it will be pinhole or perished rubber hose, or internal to the servo. You may get lucky and hear it with the engine off.
 
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