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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23001
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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My brake pedal goes down a lot more than usual but my brakes

Customer Question

My brake pedal goes down a lot more than usual but my brakes seem to work fine. After turning off the car and restarting it the trouble goes away. This has happened on 3 occasions several thousands of miles apart.
JA: How many miles are on the car? Are these the orignial brakes?
Customer: 98,500. The pads were changed at about 70,000.
JA: Are you fixing your 98 yourself? What have you tried so far?
Customer: It a 2008 MKZ. I have not tried anything yet.
JA: Anything else you want the mechanic to know before I connect you?
Customer: Yes. Recently I was traveling about 65 mph, the brake pedal was not operating normally. tje engine began to run rough and then the wrench light came on. After turning the engine off, waiting an hour, the light was off, the brakes were normal and it ran fine.
Submitted: 1 month ago.
Category: Ford
Expert:  david craig replied 1 month ago.

Hi Im David, it sounds as though the brake booster vacuum check valve is bad or the large vacuum hose from the booster to the engine is either not on all the way or has a leak or is intermittently failing. the reason i say that is because it works off of manifold vacuum from the engine and a symptom of that is a rough running engine and a soft pedal.

Customer: replied 1 month ago.
Could this cause the wrench light to come on?
Expert:  david craig replied 1 month ago.

absolutely, but you also want to put a code reader on it and make sure no other faults are pending.

Customer: replied 1 month ago.
The wrench light came on recently for the first time. The brake problem has happened 3 times many months apart.
Customer: replied 1 month ago.
I put the code reader on but it came back with 0 on the screen.
Expert:  david craig replied 1 month ago.

is the wrench light on now?

Customer: replied 1 month ago.
No.
Expert:  david craig replied 1 month ago.

you've put about 30,000 miles on your vehicle since the last time you had pads replaced. you need to replace the pads and possibly the rotors as worn pads and rotors will cause a lower pedal also.

Customer: replied 1 month ago.
The low pedal only happens periodically. If I need pad and new rotors I should have a low pedal all the time. Usually the pedal is fine. I'll check it out but this doesn't sound like the cause of my problem. I'll also check out the large hose to the booster.
Expert:  david craig replied 1 month ago.

ok. well let me know. believe me after 30,000 miles you need pads

Customer: replied 1 month ago.
Thanks for your advice. I'll check it out.
Expert:  david craig replied 1 month ago.

you bet. please let me know what you find. there are other ways to check your booster, but check those things first

Expert:  david craig replied 1 month ago.

just checking in to see how its going

Customer: replied 1 month ago.
I visually checked the hose and see no problem. Is there a way to check the check valve or do I just need to replace it?
Expert:  david craig replied 1 month ago.

you can pull the valve off and blow through it. you should only be able to blow through it on one side.

Expert:  david craig replied 1 month ago.

hows the valve?

Customer: replied 1 month ago.
My car is in the body shop all next week so I can't get to the valve until I get it back.
Expert:  david craig replied 1 month ago.

ok.

Customer: replied 1 month ago.
My car will be in the body shop until Tuesday.
Expert:  david craig replied 1 month ago.

ok, ill be waiting to hear back from you.