tnscmatt

The initial symptom was the car would shake during the first few miles after start.


Then I noticed I would have to press the brake pedal hard to get it to start. I could barely press it until after it started. Then it would soften up to normal.


Repair guy said the left front caliper was gripping the rotor when the car was off. He replaced the caliper. Still have the problem.


I think there is something in the master cylinder or brake booster area of the car.


Why would there be pressure in the system when the car is off?

Kris9884

iTrader: (3)

Pressure while the car is off isn't a bad thing BUT it shouldn't be rock hard as you describe. I would replace the master cylinder next, I doubt its the brake booster, those don't tend to go bad almost ever. Maybe a clogged line or another seized caliper?

crookncastle

brake booster check valve faulty, not allowing booster to hold vacuum for power assist when car was off.

SonicVQ

^^^ That is the issue. It also creates a large intake leak which will make the car idle very rough.

To test: Remove the large rubber hose from the brake booster and plug it.
Start the car and see if it idles normally. I suspect it will.

tnscmatt

Certainly makes sense......I am trying to find the part number by searching the usual websites - cant find it....ideas?

SonicVQ

Hmmm... in looking at the parts diagram (47210), the check valve may be part of the diaphragm, part number D7210-EY03C, listing for $800 (You didn't state the year of your G, so I assumed 2011)