Our 2015 MCS isn’t a daily driver. When it sits for two or three weeks, I find the brake pedal very stiff, so stiff that it won’t easily allow the ignition to engage. A hard press or two allows enough play in the pedal for the ignition. After that the car functions normally, day after day, until it has to sit again for weeks. The dealer service writer had no clue, hoping the experts here can offer some insights.

Cheers!

 

Don't know the answer. But wouldn't it be the job of the service writer to note that info on a work order and have a technician look at it? I'd look for a good indy shop and let them check.

 

I’ll inquire, but the dealer service tech did not find a problem. Unless I let the car sit at the dealer for weeks, they won’t experience they symptom to know where to look for a problem. Was hoping someone here had the same experience and could inform a solution.

 

If you search around the Internet you will find some people with the same problem on lightly driven cars. Brake systems are pretty similar so here is a Lexus response "dealer replaced brake booster check valve which was found to be leaking". Seems like a distinct possibility that over time you get leaks in the system.

 

Yep its possible the check valve, but my guess is that the pads stick on the slider portion of the caliper shims, like surface rust from sitting. Then next to flip out that check valve.