Brakes don't work when cold!
 

About a month ago I purchased a 2011 f-150 Super cab 4x4 ecoboost. It was certified pre-owned and had 19,000 miles on it. The second week it was towed to the shop as apparently it had bad spark plugs, whole different thread. Today, I brought it to the dealer because when I first start it in the morning and put it in gear or if it sits for a few hours the brakes hardly work at slow speed for approximately 3 minutes. After it warms up their fine. When I say the brakes don't work, I mean I put it in gear and move backwards, With all my strength with both legs pushing on pedal I can barely get it to stop with the abs kicking in and the pedal staying up high and not to the floor. This happens while on flat ground, dry pavement. Anybody else experienced this because dealer is so far not able to duplicate problem and I think there starting to think I'm crazy. What freaked me out recently is I backed down my driveway not thinking and almost hit my mailbox but swerved and got it stopped while in my neighbors yard. Any help or thoughts with similar issues would be greatly appreciated!

Did a quick search on it and it may have to deal with moisture or a broken hose somewhere. Take it to the dealer for diagnosis.

sounds like a vacuum leak in the booster maybe?

Try pulling the vacuum hose off the booster to see if it feels the same way as what you are finding when it is cold.

*update. Dealer called after having truck for week and said they couldn't duplicate the problem. I went in, got my keys, cashier etc. and started truck and drove backwards and immediately noticed brakes not working and or no boost assist like described above. Mechanic came out, hooked up cpu and we drove it. He was looking for an abs problem and not a booster/vacuum problem as I told them when I dropped off. So, they told me to leave truck and mechanic could pin point problem in morning and they now seen what I was talking about. Moved everything back to my rental car again. After that, I watched the porter back my truck into another car on the lot damaging both vehicles. My truck now needs new bumper, bedside, taillight, etc..... And edge he hit easily needs 4k in work. Just my luck. Also, porter complained of brakes not working right and the exact reason I brought the truck in and they couldn't diagnose...... I'm at my wits end here, do believe I need to contact an attorney at this point.....

Well the bright side is they know there is a problem now.

Are they giving you any guff about doing the body work?

I have to admit - I chuckled.

I just had an experience with a body shop here after recent hail storm. You're not alone with all the BS and shenanigans that auto professionals put us through!

What is your location?

Is the dealer accepting responsibility for the damage?

i have a 2013 Platinum with about 10,000 miles and this just happened to me, not related to the weather. Dropped it off at the dealership on Saturday. They looked at it today and couldn't find anything wrong. They are checking with Ford. I guess will make sure my seat belt is on, maybe wear a helmet and have a lawyers number on speed dial.

Is yours an Ecoboost too? If so, I can guess where to start looking - there should be a check valve in the vacuum line going to the booster that may be sticking and allowing the booster to pressurize when the turbos spool up. Just a wild-ass guess.

2 users in this post both report the same problem, but both are new members with a 1 or 2 post count. I just gotta point out the possibility of a shill here.......

*2nd update dealer is in Michigan, They are accepting responsibility and told me there fixing but I still don't have truck back. No shill hear, real deal. They did tell me about the valve mentioned above and replacing booster now. I've called the service writer as truck was supposed to be done and nothing. Called my ford area manager and she never called back. Apparently nobody cares at customer service at the dealer or ford level. When I originally put post up I said cold meaning truck had not ran for a while and not cold temps because twice it happened and was above 50 degrees but was unable to change after post. I'm a life long ford owner and this was my 11th ford new or used and has been extremely frustrating. There is a real problem here with brake boost in Eco boost f150's just not sure how widespread it is but freaks you out the first time it happens and you don't have power assist brakes and a 6,000 lb truck on an incline.

Damage Picture
 

Here's a picture, The angle doesn't show all the damage. bumper, quarter panel, taillight all damaged....

https://www.f150online.com/forums/me...5-imag0760.jpg

The brake booster has nothing to do with the engine choice.

Sounds like you got a bad booster that was leaking, thereby depleting your vacuum boost power. If the dealer mentioned a "bad valve" they might have been referencing the valve body in the booster. Not sure if the dealer would be that knowledgeable. But if a valve body was bad it could cause an air leak when cold.

Did you ever hear air noise in the cab? Like air sucking through a small crack?

Not necessarily. If the check valve sticks, a turbocharged engine can apply positive pressure to the booster, not just deplete vacuum like with a NA engine. Even with no vacuum, you should at least be able to stop the vehicle - with positive pressure in the booster it seems to me like that would actually fight you.

Exactly. It will just be harder to stop = applying more pressure to the brake pedal. You will stop.

Like in the days when Powered Assisted Brakes was a luxury option at one point in time. Just like when ABS was a luxury option too.