Brake problems....maybe...
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Brake problems....maybe...
Ok, just bought a '79 f150 4 wheel drive. When I bought it it had brakes that you had to pump to get to work. I could hear the power booster sucking air, so I put on a powerbooster/master-cylinder set (along with 3 new brake lines), bled out all the old fluid replacing it with new, adjusted out the rear brake shoes. It now brakes, but not hard...now, having driven many older fords in my life, most of which had better brakes, but this is my first 4WD f150.
Is the weak braking normal, or am I missing an adjustment...
PS: I also adjusted the booster push-rod as it was detailed in the manual and bench-bled the MC.
Thanks in advance.
Is the weak braking normal, or am I missing an adjustment...
PS: I also adjusted the booster push-rod as it was detailed in the manual and bench-bled the MC.
Thanks in advance.
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Joined: Jan 2003
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From: Addison,Texas
I would get it going in a parking lot or something, apply the parking break and switch into drive. See how it runs and how much gas you have to apply to get it to move. Then back up to the same spot and do it again, except holding down the brake pedal instead of the parking break. 's it worse? Better? The same?
If the parking brake is better, you've definately got a problem. There's no pressure to the system or the brakes are bad all around. If it's the same, the front brakes aren't braking. If the regular brakes are better...?
The braking ought to be similar. Disc brakes in the front and drums in the rear, and the transmission is expending the same amount of energy. Is the stopping distance way way worse?
I am assuming you've got no pedal fade, and you're not leaking somewhere and the brake fluid level in the master cylinder isn't dropping. The proportioning valve might be clogged. The new MC might have been bad to start with or you may simply need a new set of calipers on the front.
ash
['.']
If the parking brake is better, you've definately got a problem. There's no pressure to the system or the brakes are bad all around. If it's the same, the front brakes aren't braking. If the regular brakes are better...?
The braking ought to be similar. Disc brakes in the front and drums in the rear, and the transmission is expending the same amount of energy. Is the stopping distance way way worse?
I am assuming you've got no pedal fade, and you're not leaking somewhere and the brake fluid level in the master cylinder isn't dropping. The proportioning valve might be clogged. The new MC might have been bad to start with or you may simply need a new set of calipers on the front.
ash
['.']
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Joined: Mar 2003
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Did you bleed the brakes with the pin on the front of the proportioning valve pulled out slightly? This offsets the internal plunger so that all brakes, especially the rears, can be properly bled. You may also need to bleed the brakes one more time, maybe let good old gravity do some of the bleeding.
I went through the brakes on my truck just as you did, except I would up replacing everything from the firewall on down. Once I started replacing a couple of items, it only highlighted the remaining old/weak components. Well worth it for a dependable system. You may need to replace the proportioning valve as well - after some years they may still work, but not as well.
I have also had rebuilt MC's just not work very well right out of the box - for the small $$ difference I always buy a new one.
The pad and shoe material can also make a difference. I like Performance Friction stuff better than standard and also better than regular semi-metallic. Semi-metallic like heat to work well - I did not like the brakes being sort of marginal until they reached temp.
Just some thoughts.
I went through the brakes on my truck just as you did, except I would up replacing everything from the firewall on down. Once I started replacing a couple of items, it only highlighted the remaining old/weak components. Well worth it for a dependable system. You may need to replace the proportioning valve as well - after some years they may still work, but not as well.
I have also had rebuilt MC's just not work very well right out of the box - for the small $$ difference I always buy a new one.
The pad and shoe material can also make a difference. I like Performance Friction stuff better than standard and also better than regular semi-metallic. Semi-metallic like heat to work well - I did not like the brakes being sort of marginal until they reached temp.
Just some thoughts.
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I got it...finally
thanks all, I finally found the problem...The instructions that came with the power booster told ya how to adjust the rod length, however, on another post I found a diagram telling the distance from the facing plate to the end of the pushrod.
It turns out that the adjustment that the manual had was almost a full turn too short, I adjusted it out further and have GOOD brakes now...
It turns out that the adjustment that the manual had was almost a full turn too short, I adjusted it out further and have GOOD brakes now...
