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hard then soft brake pedal


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strange issue..

 

Did a complete brake job on wifes car, front and rear rotors and brake pads all around!

now, when I go to start the car after sitting overnight, the brake pedal is fairly hard to push.. so when I go to start the car I notice I have to push it much harder than normal!

when car starts and runs the pedal is soft (brakes work fine)..  go to Walmart, shop for hourish go to start car and pedal is soft.

 

NOW...leave car overnight again and and go to start it in morning and pedal is stiff and have to push noticeably push hard to start car.

 

not a major issue but definitely noticeable!!

Edited by wpginterceptor
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Vacuum booster has check valve so it holds  vacuum for a period of time...say a Wallymart shopping visit for 2 hrs so assist still there on restart.

 

Over night especially in winter,  vacuum lost and engine needs few seconds to recharge booster, so initial stiff pedal.

If pedal pressure is varying while driving, could be a master cyclinder issue.

 

Since about 1969 all master cyclinders are two stage design (probably US federal gov safety mandate).  If primary seal fails, the pedal almost to the floor will still have a large amount of braking ability. Not full since back up stage is smaller bore, but enough to theoretically stop car.

My first car a 1967 beetle had four drum brakes and a single stage master cyclinder; but a working hand brake got me home once.

So it is important to pay close attention to how well your brakes operate. Minimum standard ahhh no.

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  • 1 year later...
On 6/6/2020 at 12:17 PM, wpginterceptor said:

strange issue..

 

Did a complete brake job on wifes car, front and rear rotors and brake pads all around!

now, when I go to start the car after sitting overnight, the brake pedal is fairly hard to push.. so when I go to start the car I notice I have to push it much harder than normal!

when car starts and runs the pedal is soft (brakes work fine)..  go to Walmart, shop for hourish go to start car and pedal is soft.

 

NOW...leave car overnight again and and go to start it in morning and pedal is stiff and have to push noticeably push hard to start car.

 

not a major issue but definitely noticeable!!

I know this is an old post but I was wondering if you ever solved this problem? Mine does the exact same thing and the brake pedal is so hard after sitting overnight that I can't push it down, and it won't start unless the brake is depressed and I literally have to force it down hard to start it. The temperature doesn't seem to matter as mine has done it in my warm condo underground. It doesn't appear to be a vacuum problem but more of a brake fluid problem from forcing the brake caliper pistons back when a brake job is done because mine only started doing this after front/ back rotors and pads were replaced. The dealer say's the typical "this is normal" and "you probably never noticed it before" It's my 3rd. Dodge Journey and it's not normal. Is it possible there is air in the brake lines and over time the hydraulic effect of the air slowly pushes the brake pads out while sitting pushing the pads tight against the rotors? or did you find a solution?  Thanks in advance.

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