OK - I'm going to guess that the fluid is original. I just noticed in the manual that it should be changed every 24 months. It may actually be 168 month old!Probably high water/moisture content of brake fluid and when hot water boils and makes it spongy. I have seen this before with an old Honda Accord.
New fluid, bleeding at the calipers and wheel cyl. should do the trick. At least 1 qt. or more needed of fluid or 3-4 small containers. Suck the old out of the master cylinder to get most out before you begin.
If that doesn't fix it then it is time for a new master cylinder.
Can he tell if that plunger moves on the HCU like on bubble bodies?This generation of ford products have a bad track record with internal ABS leaks in the HCU. If you have no fluid leaks this is your most likely problem.
Can he tell if that plunger moves on the HCU like on bubble bodies?
Remember to bleed the caliper furthest from the master cylinder then as you go.2009 Mercury Mariner has recently begun having an intermittent spongy brake pedal. Has 70k miles.
I'm planning on new fluid and bleeding this weekend. Should I be looking elsewhere?
Thanks!