No Power Brakes on Startup - Normal?
05-29-2014, 09:49 PM
#1
Senior Member
Thread Starter
No Power Brakes on Startup - Normal?
I park on my driveway, which is pretty steep. If I fire up the engine, put my foot on the brake, pop the parking brake, drop it into reverse and start rolling backwards, normal brake pressure is useless and I roll back into the street until I jam the brake pedal HARD.
This only happens when I'm in a hurry and the engine is still winding down from the start-up RPM. If I start the engine, then fasten seat belt, plug in the phone, tune the radio, powder my nose, etc., then the brakes function as normal. It's only when I start-and-go that this is a problem. One time, I made it all the way across the street, barely stopping before I creamed the neighbor's retaining wall. Just glad there was no cross-traffic!
When I'm standing on the brake, head pushed against the roof for leverage, the pedal softens and normal braking begins. You can stop, but the pressure required is a big surprise and it feels like you're stopping without power assist.
My best guess is that my power brake takes 10-20 seconds to begin functioning, but that leads to my question "Is this normal?"
This only happens when I'm in a hurry and the engine is still winding down from the start-up RPM. If I start the engine, then fasten seat belt, plug in the phone, tune the radio, powder my nose, etc., then the brakes function as normal. It's only when I start-and-go that this is a problem. One time, I made it all the way across the street, barely stopping before I creamed the neighbor's retaining wall. Just glad there was no cross-traffic!
When I'm standing on the brake, head pushed against the roof for leverage, the pedal softens and normal braking begins. You can stop, but the pressure required is a big surprise and it feels like you're stopping without power assist.
My best guess is that my power brake takes 10-20 seconds to begin functioning, but that leads to my question "Is this normal?"
05-30-2014, 08:24 AM
#2
I don't think that is normal.. If the brakes work good under normal operating conditions, I'd be inclined to give the vacuum line feeding the booster a look. The check valve may not be seating very well when the brakes are applied. It sounds like it gets a good work out considering your living with a steep driveway..
In normal operating conditions try holding the brake in drive while idling for a good 20 seconds.. If the pedal starts to sag a bit after holding steady then there could be an issue with that check valve or the O ring it seats in on the booster...
It could also be a sign that the brake fluid could use a good bleeding....
With a steep driveway, you might want to consider laying a sandbag down or pouring a lump of tar in the driveway to take some of the stress off your braking system and tranny.. Use it like a wheel chock when parking.... You could also dig down and create a divot if a lump will give you problems entering a garage..
When parking on steep inclines, cold starts can also be quite taxing on a vehicle when done everyday....
In normal operating conditions try holding the brake in drive while idling for a good 20 seconds.. If the pedal starts to sag a bit after holding steady then there could be an issue with that check valve or the O ring it seats in on the booster...
It could also be a sign that the brake fluid could use a good bleeding....
With a steep driveway, you might want to consider laying a sandbag down or pouring a lump of tar in the driveway to take some of the stress off your braking system and tranny.. Use it like a wheel chock when parking.... You could also dig down and create a divot if a lump will give you problems entering a garage..
When parking on steep inclines, cold starts can also be quite taxing on a vehicle when done everyday....
05-30-2014, 10:56 AM
#3
Senior Member
Certainly not normal. My 05 has full brake assist almost immediately upon starting. Now I have a question for you and I'm not trying to be a wisea** but why haven't you taken this in for a professional diagnosis? Years ago I had a Jeep and the brakes were getting weak/soft. I knew it was the master cylinder but put it off. It finally failed completely when I was pulling into a friends driveway. I managed to miss his garage and put it into the backyard fence, but it could have been tragic/deadly had it failed elsewhere. I agree with E86 above, that its probably vacuum related. If the supply line is OK you need to get a vacuum pump and check the booster. From what you describe, its my first suspect.
05-30-2014, 12:28 PM
#4
Senior Member
Not that unusual actually and my FIL complain of the same thing on his Dodge but he jumps in and almost has it in gear before the starter has stopped turning.
As your engine revs higher you lose vacuum. On immediate start up, the engines revs a little higher and reduces available vacuum to recharge the booster, it needs a lot of vacuum. This should only take a very short period of time to fully boost.
If this sounds like you, jumping in and trying to go, then no biggie.
FWIW I would never do that to any of my vehicles. I allow at least until the engine RPMs come down. I do this just to ensure full circulation of oil in both engine and trans. In the summer 10 seconds should do it but in cold temps I will wait up to 30 seconds or a minute in really cold temps.
As your engine revs higher you lose vacuum. On immediate start up, the engines revs a little higher and reduces available vacuum to recharge the booster, it needs a lot of vacuum. This should only take a very short period of time to fully boost.
If this sounds like you, jumping in and trying to go, then no biggie.
FWIW I would never do that to any of my vehicles. I allow at least until the engine RPMs come down. I do this just to ensure full circulation of oil in both engine and trans. In the summer 10 seconds should do it but in cold temps I will wait up to 30 seconds or a minute in really cold temps.
05-30-2014, 12:39 PM
#5
Senior Member
I agree with a brief period of warm up and allowing systems to get situated before driving off. As far as manifold vacuum though, since the engine is under no load the vacuum is every bit as high during the ramp up phase as it is at idle. I would bet its at least 20 inches. FWIW my 05 holds vac. all night and has enough for one assisted pedal stroke prior to starting.
05-30-2014, 09:55 PM
#7
Senior Member
Thread Starter
Good advice and thanks to all. It ain't normal.
I tested again today and you can feel it even if you don't pop the parking and go into gear. If you get in the truck with engine off, after an overnight or even two, the brake is hard. Barely compresses at all. Within 10 seconds or so of engine on, it softens and functions as expected.
During the day, it won't do this at a grocery or gas station stop, or even a 3-4 hour appointment. Only if it's 12+ hours. maybe even a 24 hour layover (I don't drive it every day).
My mileage is still low, but at 7 years old, the rubber could be deteriorating. Sounds like it's time for some diagnostics.
And Perry, no offence taken. That's kind of reason for the thread. For all I know there is a warning in the owners manual that says the brakes don't work when you first start up!
I tested again today and you can feel it even if you don't pop the parking and go into gear. If you get in the truck with engine off, after an overnight or even two, the brake is hard. Barely compresses at all. Within 10 seconds or so of engine on, it softens and functions as expected.
During the day, it won't do this at a grocery or gas station stop, or even a 3-4 hour appointment. Only if it's 12+ hours. maybe even a 24 hour layover (I don't drive it every day).
My mileage is still low, but at 7 years old, the rubber could be deteriorating. Sounds like it's time for some diagnostics.
And Perry, no offence taken. That's kind of reason for the thread. For all I know there is a warning in the owners manual that says the brakes don't work when you first start up!
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06-01-2014, 05:54 AM
#10
Run your VIN at www.etis.ford.com to find out.