Hard brakes first thing in the morning.

[G8Master]

Hi all,

My 2007 C180k has developed a fault were first thing in the mornings (especially when cold) when I first start the car the brake pedal is extremely hard to push, only when the engine has been running for 10-15 seconds am I able to push the pedal easily.

The brakes work fine after this point.

From some of the posts I have read it looks like I may have a faulty Brake Booster or possibly a defective Brake Boost check valve.

Before I condemn the brake booster, I would like to test/replace the brake boost check valve. Is this easy enough to do? How much do you think this would cost to get done at an Indy?

Thanks

 

[Dieselman]

Surely this is just a case of the vacuum slowly leaking away overnight and the car starting on fast idle, so taking longer to build enough vacuum.
If anything I would think the intake system has a vacuum leak.

 

[Beno]

As DM says

 

[panason1c]

You should be able to hear a 'hissing' from the servo/system if it is leaking.............Run the engine, and then stop the engine, and listen carefully for any air leaks around the brake booster and associated pipework, particularly from inside the car in the area of the brake pedal push rod where it enters the booster, as sometimes the seal around the push rod can fail and cause loss of vacuum.

It is probably worse when cold due to the seal becoming harder/contracting when below certain temps.

 

[G8Master]

Thanks for your replies. I will have another listen in the morning. I couldn't hear any hissing around the brake booster and associated pipework when I checked earlier.

 

[panason1c]

Thanks for your replies. I will have another listen in the morning. I couldn't hear any hissing around the brake booster and associated pipework when I checked earlier.

While you're listening from inside the car, just very lightly 'jiggle' the brake pedal and listen out for any hissing near to it.