Air noise??
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
If you have power brakes, there is a big round canister, about 10 inches in diameter, mounted on the firewall. The brake master cylinder mounts to it. It could be leaking and letting vacuum which assists it, to escape.
Are you losing any effectiveness while braking? Meaning, does it require more effort than before you started hearing "air"?
Have you attempted to look under the dash to perhaps trace where the sound is coming from? C'mon, you did right? Please don't tell us that posting your question on FTE was your first step in troubleshooting. Have some skin in the game, please.
Are you losing any effectiveness while braking? Meaning, does it require more effort than before you started hearing "air"?
Have you attempted to look under the dash to perhaps trace where the sound is coming from? C'mon, you did right? Please don't tell us that posting your question on FTE was your first step in troubleshooting. Have some skin in the game, please.
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
It is the brake booster going bad. The rupture in it's rubber diaphragm is leaking enough vacuum to make the noise but not bad enough to be a major vacuum leak for the engine and to quit assisting your brakes. Unless the master cylinder has been replaced recently, I suggest you buy a master/booster combo unit.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 783
From: Simi Valley, CA
It is the brake booster going bad. The rupture in it's rubber diaphragm is leaking enough vacuum to make the noise but not bad enough to be a major vacuum leak for the engine and to quit assisting your brakes. Unless the master cylinder has been replaced recently, I suggest you buy a master/booster combo unit.
Plastic check valve may be cracked and/or rubber grommet age cracked, air escapes. Over time, rubber vacuum hoses tend to crack where they are clamped on, air escapes.
But, before the OP replaces anything brake related on his 1970 F250 2WD, he needs to find out which type of power brakes it has.
Does it have front drum brakes or does it have optional dual piston caliper front disc brakes? Booster different, master cylinder different, check valve different.
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gitane59
1999 - 2016 Super Duty
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Jun 12, 2006 01:42 AM
