PV question...
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PV question...
I just went through my haynes, and discovered that i am supposed to open up the PV in order to bleed the brakes... can someone shed some more light on this for me as i did not have to do anything to get fluid to flow right out of the front calipers when i bled them the other day, im trying to trouble shoot why i have WEAK braking power only in the last 2 inches before the brake pedal hits the fire wall...
1973 f100 302 2wd disc/drum manual brakes
1973 f100 302 2wd disc/drum manual brakes
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by opening up its refering to something i use to allow fluid to move out of the PV but i dont know in specific what its refering to or if its 'open' and i close it i can get some more brake pedal?
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
It's talking about the pin on the front of the proportioning valve. You're supposed to pull it out and hold it there while you bleed the fronts. This opens the metering valve (which is one component of the proportioning valve) all the way so that fluid can go right past, making sure there isn't any air trapped in the metering valve.
The metering valve is responsible for the delay between the front and rear brakes in a disc/drum setup. The brake shoes for the rear brakes have to travel a small distance before they make full contact with the drum, whereas the brake shoes for the front brakes ride the rotor surface at all times.
The metering valve is responsible for the delay between the front and rear brakes in a disc/drum setup. The brake shoes for the rear brakes have to travel a small distance before they make full contact with the drum, whereas the brake shoes for the front brakes ride the rotor surface at all times.
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It's talking about the pin on the front of the proportioning valve. You're supposed to pull it out and hold it there while you bleed the fronts. This opens the metering valve (which is one component of the proportioning valve) all the way so that fluid can go right past, making sure there isn't any air trapped in the metering valve.
The metering valve is responsible for the delay between the front and rear brakes in a disc/drum setup. The brake shoes for the rear brakes have to travel a small distance before they make full contact with the drum, whereas the brake shoes for the front brakes ride the rotor surface at all times.
The metering valve is responsible for the delay between the front and rear brakes in a disc/drum setup. The brake shoes for the rear brakes have to travel a small distance before they make full contact with the drum, whereas the brake shoes for the front brakes ride the rotor surface at all times.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
It's definitely a good sign that fluid is getting to the calipers, but it's still possible for air to be trapped in the metering valve. When it comes to this issue, instead of wondering whether or not having skipped a step can contribute to a problem, it's best just to do it correctly in the first place. That way you don't set yourself out on a wild goose chase.
To answer your question, is the pedal spongy at all? Can you pump the pedal several times to build pressure, or does it behave consistently? Was anything recently replaced that lead to this problem?
Proportioning valves have the lowest failure rate of the entire braking system. The most common reason people replace them is because they're trying to chase down a mysterious soft pedal issue, and it's the only part they haven't replaced. While they do fail, at this point if you're getting fluid to all four wheels, there are some other more common areas to look at first.
To answer your question, is the pedal spongy at all? Can you pump the pedal several times to build pressure, or does it behave consistently? Was anything recently replaced that lead to this problem?
Proportioning valves have the lowest failure rate of the entire braking system. The most common reason people replace them is because they're trying to chase down a mysterious soft pedal issue, and it's the only part they haven't replaced. While they do fail, at this point if you're getting fluid to all four wheels, there are some other more common areas to look at first.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,326
Likes: 48
From: Middle TN
The most common reason for low pedal is that the rear brake shoes are not adjusted correctly. You must run the adjusters all the way out until it locks the wheel from turning, Then use a skinny screwdriver through the adjuster slot to unseat the ratchet and allow you to reverse the adjuster until there is just the slightest drag when rotating the wheel.
Do this before you bleed or look for other problems.
Do this before you bleed or look for other problems.
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Senior User
Joined: Aug 2010
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It's definitely a good sign that fluid is getting to the calipers, but it's still possible for air to be trapped in the metering valve. When it comes to this issue, instead of wondering whether or not having skipped a step can contribute to a problem, it's best just to do it correctly in the first place. That way you don't set yourself out on a wild goose chase.
To answer your question, is the pedal spongy at all? Can you pump the pedal several times to build pressure, or does it behave consistently? Was anything recently replaced that lead to this problem?
Proportioning valves have the lowest failure rate of the entire braking system. The most common reason people replace them is because they're trying to chase down a mysterious soft pedal issue, and it's the only part they haven't replaced. While they do fail, at this point if you're getting fluid to all four wheels, there are some other more common areas to look at first.
To answer your question, is the pedal spongy at all? Can you pump the pedal several times to build pressure, or does it behave consistently? Was anything recently replaced that lead to this problem?
Proportioning valves have the lowest failure rate of the entire braking system. The most common reason people replace them is because they're trying to chase down a mysterious soft pedal issue, and it's the only part they haven't replaced. While they do fail, at this point if you're getting fluid to all four wheels, there are some other more common areas to look at first.
while bleeding the brakes, the noticed that i was able to build pressure, even while bleeding them, the pedal wouldnt go all the way to the floor... i thought this was a good sign... but after 3 attempts of bleeding, pedal is super spongy still. i can pump them a couple times and there is pressure... but when i am driving it, it almost feels like the front brakes arent working and im creeping to a stop on the rears... not sure though
from all the threads ive read, the PV is in most cases self adjusting and an almost never fail component. i simply asked because when i went to look under the truck, the cable wasnt connected and the when i felt around the PV i noticed that i could pull the part out a little, i was just curious about that.
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The most common reason for low pedal is that the rear brake shoes are not adjusted correctly. You must run the adjusters all the way out until it locks the wheel from turning, Then use a skinny screwdriver through the adjuster slot to unseat the ratchet and allow you to reverse the adjuster until there is just the slightest drag when rotating the wheel.
Do this before you bleed or look for other problems.
Do this before you bleed or look for other problems.
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