Soft Brakes and poor idle problem connected?
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From: Central Texas
Soft Brakes and poor idle problem connected?
Both problems started 2 days ago.
Idle is really rough - it has died a couple of times when stopping. At the same time, the brakes got really soft.
Checking the master cylinder, the front res was empty - it has been refilled - but found no signs of leaks anywhere along the brake system.
Are the two problems related, or should I attack each separately??
Idle is really rough - it has died a couple of times when stopping. At the same time, the brakes got really soft.
Checking the master cylinder, the front res was empty - it has been refilled - but found no signs of leaks anywhere along the brake system.
Are the two problems related, or should I attack each separately??
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Senior User
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From: Central Texas
Booster is attached to manifold vacuum.
Drove with the vac hose to the brake booster disconnected and plugged.
The brakes still had to be pumped a couple of times before they would engage, but they did engage. Just like with the booster attached to vac, but harder to push the pedal.
Not seeing any difference in the idle with the booster disconnected.
Drove with the vac hose to the brake booster disconnected and plugged.
The brakes still had to be pumped a couple of times before they would engage, but they did engage. Just like with the booster attached to vac, but harder to push the pedal.
Not seeing any difference in the idle with the booster disconnected.
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
If you have enough slack in the brake lines to unbolt the master cylinder and slide it forward some, try and see if the rear seal on the MC is leaking. The fluid didn't just disappear. Maybe the seal leaked and the booster took in the fluid, putting brake fluid into the combustion stream. Try idling it with a vacuum gauge connected to manifold vacuum, and see what the gauge says.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,326
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From: Middle TN
I would think it would draw from the rear portion of the res if the booster was bad?
If the front res was dry then you need to bleed the rear brakes to get the air bubble out of the line. Watch the res close cause it will run dry quick when bleeding the rear brakes.
If the front res was dry then you need to bleed the rear brakes to get the air bubble out of the line. Watch the res close cause it will run dry quick when bleeding the rear brakes.
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From: Central Texas
Rear needed to be bled. After drilling the rust out of all four bleed screws, bled the system and the rear seemed to have all the air. Working fine now and did not have any connection to the rough idle problem.
Thanks for all y'alls help.
Thanks for all y'alls help.
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mattthegreat
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Jan 17, 2010 04:27 PM
