ReelEmbedded

Sorry for the long first post, but I'm trying to provide all of the details for other people to help/learn.

Recently, I was driving to work and had the check brake system message show up on my dash and the brake light on the dash too. The brake boost seemed to have quit working and the pedal was hard which resulted in much longer stopping distances. Luckily, I didn't crash. I pulled over as soon as I could and checked my brake fluid and everything was fine. When I restarted the truck, the brakes functioned normally. I probably shouldn't have, but I finished my commute (much more cautiously) and everything seemed fine. Then on the way home, same thing happened. I then had the truck towed to the dealership to have it fixed.

The truck is now at the dealer for the second day and they're telling me they can't reproduce the symptoms and the brake system looks OK. If they can't find anything, they'll send me on my way and I'll have to worry if/when this will happen again.

I'm hoping someone can help me point them in the right direction.

My Truck:
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- 2013 F150 Super Crew 4x4 Ecoboost Lariat w/ ~49K miles.
- Built July 1, 2013 at Dearborn plant (1 month before recall)
-https://media.ford.com/content/fordm...ety-compl.html
- Had IWE's replaced in December since they were making noises.

What I Know:
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- Weather was raining and upper 30's (no snow).
- I live at ~6800ft.
- Check brake system message came on dash and brake light too.
- Brake pedal became difficult to push (hard pedal).
- Brake booster tried kicking in kind of like pulsing of ABS.
- First time I was driving about 30-40mph first time. ~ 8mi from my house.
- Second time stopped at a light. ~7mi from start.
- Plenty of brake fluid in reservoir.
- Worked OK for a little while after powering truck down for a few minutes.

What Dealership Found:
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- DTC Code C109D - Low Vacuum.
- Rotors, pads, calipers all look and function OK.
- Can't reproduce the issue.

Chad Walker

DTC says it right there. Low vacuum. The EB needs a pump to create vacuum. I don't believe there is a recall or extended warranty on '13-14 trucks regarding the pump since it was changed.

soaringfalcon

iTrader: (1)

Everything you described is due to the brake booster not functioning due to low or no vacuum, and DTC C109D confirms this.


The 13-14 have a mechanical vacuum pump, I have not hear of many of them having issues, but it's possible. However, more than likely though it's probably an issue with a cracked vacuum line.
If your dealer cannot figure out the issue with the DTC telling them exactly what it is, might be time for a new dealer. It's not that hard to troubleshoot a vacuum issue.

ReelEmbedded

So I just got off the phone with the dealership and they still can't reproduce it. They've put ~80 mi on it trying to recreate the issue. They say its working perfectly.

I did ask about the vacuum and they said it checked out good.

The only thing they suggested was to keep it until Friday as we're supposed to get some rain and hook a data logger up.

What could cause the vacuum to be intermittently failing?

Chad Walker

The pump.

ReelEmbedded

So I got the truck back on Friday. The dealer replaced the brake booster after reproducing the intermittent failure while connected to a data logger.

Since then, I haven't seen any more symptoms. I'm still cautious that you guys are right about the vacuum pump. I'll update if anything changes.