help, brake problems! possible master cylinder?

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help, brake problems! possible master cylinder?

Postby beanis » 08 Jan 2008, 19:04

Hi,
Bought a chevette. the brakes felt ok but under constant pressure pedal compressed, also the rear brakes locked up very easily... i looked at brake flexi hoses to find they were bulging at both ends on all 3 hoses. bought a goodridge brake line, fitted it all today...

now: brakes do exactly the same thing as before! and lock up even easier.

couple of things also, you can only make pedal completely depress when car is running. the pedal feels fine at first, but if you let off just slightly and press again it goes further.

is this my mater cylinder, since i cant find any leaks at any of the wheels?
is the locking up back wheel the master cylinder too, or is this drum asjustment, or is it the regulator thingy for back and front brakes.

i feel at a bit of a loss,
i found this hs master cylinder on ebay, would that fit?
new master is £100 and rebuild kit is £20...how hard is it to rebuild kit?

help please! i feel im wasting days on this problem :(
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Postby Gordo » 09 Jan 2008, 09:24

First, double check you're not loosing fluid at the wheel cylinders or calipers.
What you're describing is a common symptom for a worn master cylinder seal, probably on the front* from what you say.
If the brakes are lightly applied, the sealing ring doesn't press against the bore hard enough to seal it, but when more pressure is applied, the seal design means it presses harder against the bore, sealing it.
Unfortunately, it is usually a sign of a pitted/rusted master cylinder bore as well. I normally get them machined and sleeved in brass or stainless steel by a brake reconditioning specialist and they should never give any more trouble.
If you can get a new or resleeved one, I'd use that unless you've checked the old one and it can definitely clean up with a light hone.

*Chevettes use a pressure limiting valve which should make it impossible to lock up the back brakes.
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Postby beanis » 23 Jan 2008, 20:23

can someone give me more advice please!?
i've had master cylinder reconditioned at great cost, it now works fine, i replaced rear shoes and cylinders.
replaced flexi hoses with goodridge ones.
back wheels still lock up under heavy pedal use! seems pretty dangerous.

only thing left is pressure regulator, do you think this is the problem?
i've found an old one second hand, do you think i should replace that next? i can't find a new one anywhere... :(
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Postby Doive » 23 Jan 2008, 21:34

Sounds suspiciously like the pressure regulator. As I understand it these are virtually unobtainable new or decent used, and there were at least two different types fitted to the Chevette according to whether the car has Girling or Delco hydraulics fitted. Regardless of which system it is, it could be easily re-plumbed to take a pressure limiting valve for the rear brakes, or a unit from another type of car could be incorporated.
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Postby beanis » 25 Jan 2008, 00:18

strangely enough it just passed its MOT with the problem, which makes me think its less of a problem...
bt i do still think i need to sort something, i'll look into getting something off another car to fit in the system.
cheers for advice.
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Postby Gordo » 25 Jan 2008, 12:30

Most brake machines just check for side to side balance on an axle, not the front/rear balance.

Most pressure limiting devices use a spring loaded piston method - you may be able to strip and check it's free.
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Postby Shuvit-pinto » 26 Jan 2008, 21:12

Doive wrote:there were at least two different types fitted to the Chevette according to whether the car has Girling or Delco hydraulics fitted.





More like 4 different types Dave. I have 4 hatches here and they are all different. !!! :shock:
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Postby Doive » 26 Jan 2008, 22:53

Come to think of it you are right - there are three I know of for the Girling system alone!
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