Vacuum Leak
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Prolocutor
Joined: Jan 2009
Posts: 13,618
Likes: 1,245
From: Western MA
Yep, just had my vacuum booster replaced under warranty yesterday. So far, the issue is cured. Previously they changed the vacuum hose assembly which did not cure the issue so this time they went deeper. The check valve must be intradgrul to the booster itself.
New User
Joined: Jan 2018
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How long is the vacuum expected to stay in the brake booster system under normal conditions? On my previous vehicle (a Subaru) it would remain for days, but after a week or two if I didn't drive it would bleed off and I'd have a hard pedal at start. I assumed this was normal. On my brand new 2017 F-250 (Gas), pedal is always rock hard after sitting over night, and sometimes noticeably firm after an 8 hour work day, and to me that doesn't seem normal. What's the expected performance?
-Adam
-Adam
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Prolocutor
Joined: Jan 2009
Posts: 13,618
Likes: 1,245
From: Western MA
Adam, I'm not sure there is a normal amount of time listed anywhere, but it should last longer than 24 hours for sure. Now that my booster has been replaced, I've gone 3-4 days and still had a nice soft pedal on startup. I haven't let the truck set long enough to test it longer than that. Mine started out like yours and in the end would loose it after 15-20 minutes. Then, every once in a while, it would last days again. The internal check valve must be at fault.
Senior User
Joined: Mar 2007
Posts: 242
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I wonder if it's more noticeable with the push-button start which requires the brake pedal be depressed to start? I don't think I put my foot on the brake with any of my key start vehicles while starting, so I don't know that I would have noticed it on them otherwise.
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Joined: Jan 2018
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I drove stick shift vehicles for so long that pressing the brake to start is a permanent habit for me. As a result I notice this every time even though I have key start in my XLT. Leaving work yesterday rock hard pedal. Time to call the dealer about both this and the 34 gallon tank fuel gauge issue.
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Prolocutor
Joined: Jan 2009
Posts: 13,618
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From: Western MA
If they tell you it's normal, keep pushing. It took me talking to the owner and the service manager to get my booster swapped. The tech and service writers kept telling me it was completely normal.
Tuned
Joined: Nov 2017
Posts: 264
Likes: 3
From: Bend, Oregon
Well that's a bummer. Mine has the vacuum leak also and was holding out taking it to Ford until, or if, more issues presented themselves. Now I think I'll just live with it.
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Elder User
Joined: Jun 2017
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Mine had a very small antifreeze leak, about 1 quart or 2 over 7k miles. Turned out to be a freeze plug in the head on the passenger side. I would see small drips on the driveway, turns out it would find it's way down along the track bar.
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Prolocutor
Joined: Jan 2009
Posts: 13,618
Likes: 1,245
From: Western MA
New dealers says they found the antifreeze leak. The degas bottle had a bad seal so it was a leak in the form of steam. This is why I could smell it but not see any drips. New one going in today. Will see if that cures it.
They also said that there is indeed a check valve for the master cylinder. Funny, dealer one said no such animal and replaced the whole master. Anyways, it's on national back order which may indicate they are changing a lot of them out in the wild. Will report back when that one comes in and get's swapped...
They also said that there is indeed a check valve for the master cylinder. Funny, dealer one said no such animal and replaced the whole master. Anyways, it's on national back order which may indicate they are changing a lot of them out in the wild. Will report back when that one comes in and get's swapped...