Re: Sticky brakes

["Mark Battley" <M.Battley@xxxxxxxxxx>]

Andrew asks: (for his 71 GTj)

<I suspect this could be signs a future problem.  My front brakes does not
<release itself immediately after I let go of the brake pedal.  It takes a
<leisurely second or so, depending on how hard I was pressing the pedal.

<Why is it doing this and Is this a sign of something about to happen?

<A little history -  The master cylinder and 2 booster pumps are a year old.
<The brake pad are very new (less than 1000 miles)....

Been there (in my case the rears), took me ages but eventually found it (with 
help from the Trevor Allen, I am eternally grateful!): very simple in my case.

Big Clue #1: it's a two booster system (and RHD?) The fact that it's only the 
front brakes sticking (question: how do you know that it's only the fronts??) 
narrows the options down slightly.

Starting at your foot and working towards the caliper: Could be:

1.		Master cylinder problems: make sure it has enough free play at the pedal. 
There is an adjustable length pushrod between the pedal and the MC. If there is 
not enough free play (doesn't need much, but there must be some) the brakes may 
not release reliably. Been there. The internals of the MC can also cause 
problems.

2a. Booster problem with the front booster (normally the one facing along the 
car). Sticking main piston assembly (although I'm not convinced that this would 
actually stick: there's  a lot of pressure there), or more likely the release 
valve under the air valve. Except that yours have just been rebuilt (although 
doesn't mean they are right). I rebuilt mine (which was leaking), didn't help.

2b And this is what it finally turned out to be on mine: there is a small rubber 
hose with a 90 degree bend in it that connects the air valve on the side of the 
booster to the side of the vacuum chamber furthest from the cylinder. If this 
hose gets soft with age (which isn't helped if it gets full of brake fluid from a 
leaky booster cylinder) it can collapse under vacuum, meaning that the booster 
cannot (is slow to) equalise the vaccuum to release the brakes. Pull the hose 
off, see if it looks sad, if in doubt stuff a thinner bit of hose (e.g. 
windscreen washer hose) inside and see if it helps as a temporary test... 
hopefully you will be as lucky as me! Make sure that the hose doen't kink when it 
is fitted. I recommend replacing these as a matter of course. But still be 
careful: I'm told if a new hose is too long it can kink causing the same problem.

3. Dunno if the brake light pressure switch could cause this problem. Doubt it, 
but you never know.

4. As has been already pointed out, old rubber hoses from car to caliper can 
cause problems, but would only affect one wheel.

5. Sticky pistons in the caliper, but again, only one wheel.

Good luck!

Mark Battley
Auckland, New Zealand.

1974 Alfa Romeo 2000 GTV

105/115 series GT/GTV/GTJnr home page and register at:
      http://www.geocities.com/MotorCity/1806/105GTV.HTML

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