mla Posted December 17, 2022 Share Posted December 17, 2022 I have a newly renovated 2.0e engine in my kadett c and am having problems with my front brakes (sometimes). so sometimes, not even always my front brakes slowly applies when I'm driving, to that point where I have to shift down to get somewhere to stop the car and turn it off. And as soon as i turn it off, the brakes release. So it is obviously the engine building pressure but i do have a check valve on the hose from the master cylinder servo to the intake. Any of you guys know what it might be, or have experienced the same thing ? Quote Link to comment Share on other sites More sharing options...
Jessopia74 Posted December 17, 2022 Share Posted December 17, 2022 Does the pedal drop when it does this? Could be a collapsed or weakened return spring inside the Servo Quote Link to comment Share on other sites More sharing options...
Jonathan Pounsett Posted December 18, 2022 Share Posted December 18, 2022 If they release when the engine is switched off it’s going to be vacuum related. Or is something in the front binding when it gets hot? Quote Link to comment Share on other sites More sharing options...
Sutty2006 Posted December 18, 2022 Share Posted December 18, 2022 When you say “brakes slowly apply” is it doing this without applying the brake yourself? So for example if you pull off your driveway and drive down a completely straight road without touching the pedal, do they then apply themselves to the point you can’t drive it? If so, could be a vacuum problem. If you’re applying the brakes yourself and they slowly stick on, could be anything from a collapsed brake hose, sticking calipers or a buggered master cylinder. Quote Link to comment Share on other sites More sharing options...
cam.in.head Posted December 18, 2022 Share Posted December 18, 2022 or not having enough free play in the pedal. or a blocked servo filter(or the pieces of foam bunging up the release valve that they will have been sucked through !) Quote Link to comment Share on other sites More sharing options...
1200bandit Posted December 18, 2022 Share Posted December 18, 2022 (edited) I know that the brake servo on my Manta is adjustable ( the rod going from the servo to the brake pedal) if no play in the brake pedal try to adjust it. Had this on a 1977 Z1000 on the rear calliper release the pressure and was ok for a bit ,found that the calliper was at fault. when the brakes come on (if possible) jack one wheel at a time and see which one it jamming.Release the pressure and it might give you some direction to go. Edited December 18, 2022 by 1200bandit Quote Link to comment Share on other sites More sharing options...
mla Posted December 18, 2022 Author Share Posted December 18, 2022 19 hours ago, Jessopia74 said: Does the pedal drop when it does this? Could be a collapsed or weakened return spring inside the Servo It does not, it actually gets rock solid. 7 hours ago, cam.in.head said: or not having enough free play in the pedal. or a blocked servo filter(or the pieces of foam bunging up the release valve that they will have been sucked through !) If it would be a blocked filter, wouldn't this happen every time then ? Quote Link to comment Share on other sites More sharing options...
Jonathan Pounsett Posted December 18, 2022 Share Posted December 18, 2022 You say newly renovated. Is it possible that somethings been installed the wrong way round? Check the non-return valve on the servo vacuum hose or the brake pressure control valve? Quote Link to comment Share on other sites More sharing options...
Jessopia74 Posted December 18, 2022 Share Posted December 18, 2022 24 minutes ago, mla said: It does not, it actually gets rock solid. If it would be a blocked filter, wouldn't this happen every time then ? Might be barking up the wrong tree here. ‘The servo does excerpt a small amount of force on the master cylinder when under full vacuum, however it might be that over a couple of pumps it’s not returning the master cylinder back to its proper ‘rest’ position, so it’s effectively just pumping fluid into the brake lines without returning for the fluid to return. Next couple of pumps it then hydraulic locks the brakes on. When engine is stopped, it allows the vacuum to drop off and no longer any force holding the master cylinder slightly forwards. So I would check a few things, in order of ease; 1) linkage adjustment for pedal, check it’s has a little dead zone when off. You should feel a very slight nothing, before it pushes. 2) when brakes are stuck on, engine still running, slightly crack open the union on the master cylinder to just let pressure off to confirm calipers do return. 3) Piston in the master cylinder is the right way around 4) split master cylinder off vacuum servo, and check return spring function (the one inside servo) 1 1 Quote Link to comment Share on other sites More sharing options...
mla Posted December 18, 2022 Author Share Posted December 18, 2022 2 hours ago, Jonathan Pounsett said: You say newly renovated. Is it possible that somethings been installed the wrong way round? Check the non-return valve on the servo vacuum hose or the brake pressure control valve? Where would I find a brake pressure control valve ? 2 hours ago, Jessopia74 said: Might be barking up the wrong tree here. ‘The servo does excerpt a small amount of force on the master cylinder when under full vacuum, however it might be that over a couple of pumps it’s not returning the master cylinder back to its proper ‘rest’ position, so it’s effectively just pumping fluid into the brake lines without returning for the fluid to return. Next couple of pumps it then hydraulic locks the brakes on. When engine is stopped, it allows the vacuum to drop off and no longer any force holding the master cylinder slightly forwards. So I would check a few things, in order of ease; 1) linkage adjustment for pedal, check it’s has a little dead zone when off. You should feel a very slight nothing, before it pushes. 2) when brakes are stuck on, engine still running, slightly crack open the union on the master cylinder to just let pressure off to confirm calipers do return. 3) Piston in the master cylinder is the right way around 4) split master cylinder off vacuum servo, and check return spring function (the one inside servo) Alright thank you, the way you just described my problem is exactly what iw been trying to explain 🙏 thank you Quote Link to comment Share on other sites More sharing options...
Jonathan Pounsett Posted December 19, 2022 Share Posted December 19, 2022 3 hours ago, mla said: Where would I find a brake pressure control valve ? In the engine bay, fixed to the top of the near side chassis rail. 1 Quote Link to comment Share on other sites More sharing options...
Sutty2006 Posted December 19, 2022 Share Posted December 19, 2022 Also known as the brake bias valve? Quote Link to comment Share on other sites More sharing options...
Jessopia74 Posted December 19, 2022 Share Posted December 19, 2022 16 minutes ago, Sutty2006 said: Also known as the brake bias valve? Does same job, think the real difference is one is a proportional bias valve (based on front pressure) , the other is fixed (older type) Quote Link to comment Share on other sites More sharing options...
cam.in.head Posted December 19, 2022 Share Posted December 19, 2022 On 18/12/2022 at 17:26, mla said: It does not, it actually gets rock solid. If it would be a blocked filter, wouldn't this happen every time then ? the filter is only a bit of foam. it can get blocked but usually just disintegrates ! how much free play have you got with engine off and servo pressed a few times to empty it. you should have around 6mm . 1 Quote Link to comment Share on other sites More sharing options...
®evo03 Posted December 19, 2022 Share Posted December 19, 2022 You could also touch disk, binding one is hotter, if it's later calipers, they should be serviced regularly. Sliders dry up. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.