VE poor brakes when cold

[Dozer31]

Hi All
Just sorted out some fault codes I have been dealing with for the last couple of months and now Need some help re my VE v6 when it's first started and reverse out my drive way I have to really stand on the brakes.
After a very short time afterwards (couple of mins) the brake pedal improves.

It's an 07 model all pads are Exellent but fluid needs to be changed not because it looks dirty but time it's been in there.
Would one assume the brake booster needs to be replaced given there is no external leaks ??

Thanks

 

[lout]

what pads did you fit
what is the idle like

 

[Dozer31]

Hi
Thanks for your reply.
Not sure on brand of pad I think they were from Mace, so average quality.
Car is mild cammed with tune and is rough on idle only when first started but fine shortly afterwards.
There are No vacuum leaks as I have spent a lot of time trying to diagnose a previous fault relating to lean mixture on idel which was related to O2 Pre sensors throttle body gasket and minor exhaust leak.
So that's why I feel it may be related to brake booster.

 

[lout]

does your booster have a functioning check valve on the vacuum line

 

[Dozer31]

does your booster have a functioning check valve on the vacuum line

Yes it does have a valve and has been checked for leaks.
Could be diagram inside brake booster but haven't hird any issues reported.

 

[lout]

before starting engine in the morning, pull the hose/check valve from the booster. should be a noticeable vacuum present, which you will hear, and then refit
when car has been driven for a while, repeat this and then take note if you have the hard brake pedal again until driving
it is a bit tricky to diagnose a weak check valve vs a small hole in booster diaphragm,

 

[gossie]

Put some soft pads into it.
They won’t last long though and will probably fade when used reasonably hard.

 

[Fu Manchu]

I would suggest a vacuum leak which seals up once the motor heats up and expands a bit.

Smoke test would find it.

 

[Dozer31]

Thanks All
I will look take all of these great idea's on board.
I also like the method of checking the check valve on the booster.
Another thing is as mentioned is when it's cold it runs lumpy as for about 5 or so mins then settles down and runs smooth.
If it was a vacuum leak it would defnatly through a fault code which would relate to lean mixture on idel.
Thanks All

 

[Fu Manchu]

Checking for a vacuum leak with smoke is the only way it can quickly be ruled out really.

Depending on where it is, will depend on how it affects various things. It’s possible the ECM is able to adjust things within set parameters to compensate and therefore no code is set.