No Brake Pressure
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Joined: Aug 2001
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From: Odessa, Delaware
No Brake Pressure
I recently bought a 79 F-250 2 wheel drive utility body truck. I put a new master cyclinder in and can not build up brake pressure. I bench bled the master cyclinder prior to installing it on the truck. Once I got it on the truck, I can not get any pressure or build up by pumping the brakes. I have tried bleeding the entire system at each wheel but still can't get brakes. I do not understand what could be wrong.
Craig
Craig
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Joined: Feb 2005
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Does this truck have power brakes? If so, they are a little harder to bleed. You still do it the same way but it's more difficult to get a good actuation of the master cylinder. I prefer to have someone pump the brakes several times and hold down...then I will crack open a bleeder screw and see what comes out...when you crack open the bleeder the brake pedal should go down...do not let up on the brake pedal until you close the bleeder screw back....then let up, pump up the brakes and repeat...going around to all 4 wheels...be sure to keep the master cylinder full of fluid...if it goes empty you'll be adding air back to the system. If this method doesn't work then I have to think that either the master cylinder is bad or possibly you aren't getting actuation of the master cylinder for some reason.
Good Luck!
Tracy
Good Luck!
Tracy
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Joined: Aug 2001
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From: Odessa, Delaware
Yes this truck has power brakes. The problem with trying to bleed is that the pedal never pumps up so when I crack the bleeder screw, the pedal is already down to the floor. Also, as I bleed, I get very little fluid out of the bleeder screws.
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It's typical for the pedal to be basically at the floor when you first start. The key is that even though the pedal is down it will have some pressure built up if you pump the pedal a few times and then hold down on it. Here is exactly how I do it.
1. Fill master cylinder completely up and put top on it.
2. Be sure all bleed screws are closed
3. Have someone pump the brake pedal several times and then hold down.
4. Go to passenger side rear and crack open bleed screw. Maybe not much will come out but something should bleed out a little. Make sure the person helping continues to push on the brake pedal....DO NOT RELEASE THE PEDAL YET. Tighten the bleed screw.
5. Repeat steps 4 and 5.
6. Check and refill fluid level in Master Cylinder.
7. Go to Drivers side rear and do steps 4 and 5 twice and then step 6.
8. Go to Passenger side front and do steps 4 and 5 twice and then step 6.
9. Go to Drivers side front and do steps 4 and 5 twice and then step 6.
10. You should have some brakes at this point....repeat the whole thing until all you get is fluid....no air.
If there is nothing wrong with your brake system then this system should work.
Good Luck
Tracy
1. Fill master cylinder completely up and put top on it.
2. Be sure all bleed screws are closed
3. Have someone pump the brake pedal several times and then hold down.
4. Go to passenger side rear and crack open bleed screw. Maybe not much will come out but something should bleed out a little. Make sure the person helping continues to push on the brake pedal....DO NOT RELEASE THE PEDAL YET. Tighten the bleed screw.
5. Repeat steps 4 and 5.
6. Check and refill fluid level in Master Cylinder.
7. Go to Drivers side rear and do steps 4 and 5 twice and then step 6.
8. Go to Passenger side front and do steps 4 and 5 twice and then step 6.
9. Go to Drivers side front and do steps 4 and 5 twice and then step 6.
10. You should have some brakes at this point....repeat the whole thing until all you get is fluid....no air.
If there is nothing wrong with your brake system then this system should work.
Good Luck
Tracy
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Joined: Aug 2001
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From: Odessa, Delaware
I will try it again after work today. I have bled many a brake systems but have never had a problem like this. Since all I did was replace the master cyclinder, there should be hardly any air in the system since I did not remove anything else. Could there be a problem with the proportioning valve?
Craig
Craig
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First make sure the rear brake shoes & drums are within specs and if so , are adjusted properly.Many times shoes are worn out and the drums have been turned past spec.
Then the shoes need to be brought close enough to drum on adjusting that they barely touch the drum when the wheel is turned
Normal bleed order is right rear, left rear,right front,left front
When bleeding the 79's, after doing the rears, the pin on the proportioning valve should be pulled out before bleeding the fronts.
*NOTE: Just because something is new does not make it Good.
You may have a New faulty MC.
Then the shoes need to be brought close enough to drum on adjusting that they barely touch the drum when the wheel is turned
Normal bleed order is right rear, left rear,right front,left front
When bleeding the 79's, after doing the rears, the pin on the proportioning valve should be pulled out before bleeding the fronts.
*NOTE: Just because something is new does not make it Good.
You may have a New faulty MC.
New User
Joined: Jan 2008
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No it won't do any harm.
Some guys say they don't even pull the pin and get theoir brakes to work.
I think you have a bad MC.
I bet you didn't you get one with a Stainless Steel Sleeve ?
From what I have heard They perform better & last longer & are Lifetime guaranteed.
Some guys say they don't even pull the pin and get theoir brakes to work.
I think you have a bad MC.
I bet you didn't you get one with a Stainless Steel Sleeve ?
From what I have heard They perform better & last longer & are Lifetime guaranteed.
New User
Joined: Jan 2008
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On the bench with hand pressure with no resistance is hardly the same.
That is a dual circuit piston in there, One for the front & one for the rear.
It appears one circuit is leaking as as back pressure is acquired and the fluid is coming back into the MC Reservoir.
That is a dual circuit piston in there, One for the front & one for the rear.
It appears one circuit is leaking as as back pressure is acquired and the fluid is coming back into the MC Reservoir.
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