Hello i'm currently having some issues concerning the front brakes sticking have replaced the calipers.it seems to build up pressure in the system as you drive making the brake pedal hard. But if you push the pedal down hard it seems to release the pressure. Any advice is very much appreciated

Hi - I've seen this when the flexible brake pipes were clamped with mole grips/whatever during a caliper swap. Result was like yours - the pipe was collapsed internally so would not let fluid back out of the caliper under normal braking but when you really pumped/stood on the pedal it would open up the crimped bit and let some of fluid back up into the system.

Could be as above ^^ or master cylinder sticking.

(19-08-2018, 05:43 PM)GraemeT Wrote:  Hi - I've seen this when the flexible brake pipes were clamped with mole grips/whatever during a caliper swap. Result was like yours - the pipe was collapsed internally so would not let fluid back out of the caliper under normal braking but when you really pumped/stood on the pedal it would open up the crimped bit and let some of fluid back up into the system.

Thank you Graeme T mole grips were used on the flexi brake pipes when the calipers were changed will get them changed hopefully it will cure the problem

Why did you change the callipers - because the brakes were sticking?

(20-08-2018, 06:56 AM)polar Wrote:  Why did you change the callipers - because the brakes were sticking?

Yes that is the reason why they got changed

Well it may still be the flexi hoses but you were already having a problem when you clamped the hoses to change the callipers.

The fact that if you hit the brakes again, hard, and they free off suggests the master cylinder to me - if it were the hoses it would more than likely cause the brakes to stick constantly.

(20-08-2018, 09:27 AM)polar Wrote:  Well it may still be the flexi hoses but you were already having a problem when you clamped the hoses to change the callipers.

The fact that if you hit the brakes again, hard, and they free off suggests the master cylinder to me - if it were the hoses it would more than likely cause the brakes to stick constantly.

The master cylinder was replaced have replaced the hoses today and new discs but it still does it

Test the operation of the Servo (Brake Booster) 

http://www.newtonnet.co.uk/coupe/service...p@id=12476


EDIT.

This gives more info...

https://www.ebay.co.uk/gds/How-to-Diagno...669/g.html


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(20-08-2018, 06:25 PM)keith1969 Wrote:  

(20-08-2018, 09:27 AM)polar Wrote:  Well it may still be the flexi hoses but you were already having a problem when you clamped the hoses to change the callipers.

The fact that if you hit the brakes again, hard, and they free off suggests the master cylinder to me - if it were the hoses it would more than likely cause the brakes to stick constantly.

The master cylinder was replaced have replaced the hoses today and new discs but it still does it

  i suspect suspect jj may be on to something or abs module may have sticking spools?