Having a problem with my 2013 3.5 ecoboost. When its wet or raining I lose power brake assist. Peddle stays up but goes completely hard. Makes it very hard to stop. Worried about when my wife is driving or we're hauling our trailer when it happens. I have to pull over, turn the truck off and wait a few minutes before restarting. Then everything works normal. Dealer cannot duplicate the problem.

 

Sounds like a vacuum problem so did a quick google and found this:

https://www.tc.gc.ca/en/services/roa...-failures.html

Says it only applies to 2011-2012 but describes your symptoms to the T.

 

Checked out vacuum pump. Everything with vacuum seems ok until its wet. Thinking electrical. 2013 and up were replaced with a mechanical pump. All vacuum hoses are in good shape. Truck is back at dealer. Tomorrow they're going to put it on hoist with a driver and a guy below with a power washer and making it wet. This at my insistence. Hopefully it works. I'll post the results.

 

I had this problem a couple months ago. I had driven through a puddle and it knocked a vacuum line off of my IWE. After that happened I believe it ruined a check valve and the 4wd vacuum solenoid. The brakes would randomly lose vacuum (usually at highway speeds) and I would lose power brakes for a few minutes. I replaced the vacuum pump (to fix a oil leak), the check valve located on the firewall, and the vacuum solenoid on the firewall and problem was solved!

 

Thanks I'll get the boys to check it out

 

So after being at the ford dealer for 3 days, they were unable to replicate the problem. They say they have checked everything including recalls that were already performed. I'm going to do my best to replicate it on the weekend. I have a power washer and I'm going to make it rain. Thanks for the ideas that have come my way.

 

3 times now back to ford. turns out it was a loose vacuum line to the IWE. Thanks for the suggestion.