Brake Loss After Hard Cornering

[Izso]

Ok. VR2 has consulted me. The brake pedals there, reservoir and master cylinder all not leaking.
Just the reservoir flexes.

Reservoir doesn't flex la, that's the firewall and that flexing doesn't cause the pedal to sink all the way in like that. And the problem here only happens when cornering? I really think your master cylinder is a goner. No point repairing it as the repair kit costs a little less than the whole cylinder. Replace the whole cylinder.

for older proton (wira/satria/putra), this problem is usually caused by the hose that connects between the servo body to intake plenum. there are valves (old proton have 2 valve) inside the hose that regulates air into the servo and reserve air pressure in the servo. The first time pedal pressed, the valve(s) may be opening when it should be closed causing air in the servo being pumped into the intake instead of building pressure up from intake into the servo and the first floor triggered the valve to close on second flooring of the brake pedal. not sure if persona hose has 2 or 1 valve.

Note : PLEASE BUY ORIGINAL HOSE. I observed the cheaper 3rd party product is VERY NOT GOOD AND VERY HAZARDOUS (swelling, leak, broken valves...)

That's good advice. But I don't think the Persona has the same setup as the Wira. I don't recall seeing the hose to the plenum. But need stupidcar to check it out.

Strange that it only affects him when in a corner though, if it is the hose then it should affect him in straight lines too.

 

[stupidcar]

Reservoir doesn't flex la, that's the firewall and that flexing doesn't cause the pedal to sink all the way in like that. And the problem here only happens when cornering? I really think your master cylinder is a goner. No point repairing it as the repair kit costs a little less than the whole cylinder. Replace the whole cylinder.



That's good advice. But I don't think the Persona has the same setup as the Wira. I don't recall seeing the hose to the plenum. But need stupidcar to check it out.

Strange that it only affects him when in a corner though, if it is the hose then it should affect him in straight lines too.

I think Kopi might be on to something. because in my mind logically when I corner, something happened to the air/pressure. We will have to dissect it.

Thanks Kopi.

 

[DanzEterna]

could be your slave pump (lower pump).

 

[gunnerzz]

u r losing vacuum only when cornering.
it could ne like what bro kopi said.
look at your servo and u can see a hose at its hody going to the intake manifold.this is how mass produce car's braking system.
the valve bro kopi mention is a one way valve which can be located at one of these 3 place;
-inside the vacuum hose(most common)
-inside the servo(very rare)
-at the nipple where u plug the hose at the servo

u can press along the vacuum hose and if u feel something hard,thats the valve.i did replace mine on the pajero.
like bro kopi said,only go for ori part as aftermarket wont have perfect vacuum seal at the valve.thats it for the valve part.

your car is not that old for the hose to crack but do have a look esp at both end where connection is made.

or,this might seems simple and if i am right then we will all have a laugh.its the abs working.when u brake while turning there is a higher chance for the wheel to lock up.u might be going too fast and braking too hard.abs kicks in and u might feel pulse on the brake pedal.
or,u dont actualy fast lets say 50kmh and u brake and turn.u brake hard and the sensor sense the wheel lock so it trigger the abs but right at the moment the abs trigger,yr speed drop below 20kmh.so,pedal will go all the way down but no pulse on brake pedal.
i exp this 1st hand when my waja rear abs toor gear on the hub was broken and slight hard braking will trigger the abs.

 

[stupidcar]

u r losing vacuum only when cornering.
it could ne like what bro kopi said.
look at your servo and u can see a hose at its hody going to the intake manifold.this is how mass produce car's braking system.
the valve bro kopi mention is a one way valve which can be located at one of these 3 place;
-inside the vacuum hose(most common)
-inside the servo(very rare)
-at the nipple where u plug the hose at the servo

u can press along the vacuum hose and if u feel something hard,thats the valve.i did replace mine on the pajero.
like bro kopi said,only go for ori part as aftermarket wont have perfect vacuum seal at the valve.thats it for the valve part.

your car is not that old for the hose to crack but do have a look esp at both end where connection is made.

or,this might seems simple and if i am right then we will all have a laugh.its the abs working.when u brake while turning there is a higher chance for the wheel to lock up.u might be going too fast and braking too hard.abs kicks in and u might feel pulse on the brake pedal.
or,u dont actualy fast lets say 50kmh and u brake and turn.u brake hard and the sensor sense the wheel lock so it trigger the abs but right at the moment the abs trigger,yr speed drop below 20kmh.so,pedal will go all the way down but no pulse on brake pedal.
i exp this 1st hand when my waja rear abs toor gear on the hub was broken and slight hard braking will trigger the abs.

Poorman's car no ABS dude.
Alright. Thanks. Tomorrow gonna diagnose.

 

[^pomen_GTR^]

ill say check the rear drum inside for leaking sign... abs module would not make the brake pedal goes to the floor...it will judder but not make the brake feels empty... if no leaking at rear drum..then look back at the masterpump/servo and open the masterpump to truly confirm that it doesnt leak....if leak,repair and test again on empty road...if no leak upon close inpsection,check for brakepad condition...which is sometimes already "cooked" and not working at its best performance...

 

[vr2turbo]

ill say check the rear drum inside for leaking sign... abs module would not make the brake pedal goes to the floor...it will judder but not make the brake feels empty... if no leaking at rear drum..then look back at the masterpump/servo and open the masterpump to truly confirm that it doesnt leak....if leak,repair and test again on empty road...if no leak upon close inpsection,check for brakepad condition...which is sometimes already "cooked" and not working at its best performance...

But if servo/master pump problem, the problem should happen anytime, and not only in corners, right?

 

[^pomen_GTR^]

But if servo/master pump problem, the problem should happen anytime, and not only in corners, right?

not sure if i mssread it...but he said during hard braking for corner?

if only braking while corner but not on straight,maybe need to look at brake hose near tyre..maybe got one or two that was weak or too much bending on it...

 

[vr2turbo]

not sure if i mssread it...but he said during hard braking for corner?

if only braking while corner but not on straight,maybe need to look at brake hose near tyre..maybe got one or two that was weak or too much bending on it...

Yup, got to check them,but he did do some cable tie thing to the hoses.

I suspect some movement in the wheel disc or wheel itself. If the disc rotor moves sideways it can push the piston back in then when braking, needs more fluid to push the piston back out, therefore the brakes will be lower as he mention after pumping twice it comes back up......:hmmmm:

 

[^pomen_GTR^]

Yup, got to check them,but he did do some cable tie thing to the hoses.

I suspect some movement in the wheel disc or wheel itself. If the disc rotor moves sideways it can push the piston back in then when braking, needs more fluid to push the piston back out, therefore the brakes will be lower as he mention after pumping twice it comes back up......:hmmmm:

could be due to jammed floating pin at the brake caliper aswell...

 

[vr2turbo]

could be due to jammed floating pin at the brake caliper aswell...

If floating pin is jam he may even have overheated brakes....