Brake bleeding issue. Possibly
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Junior User
Joined: Jul 2014
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Brake bleeding issue. Possibly
76 high boy. Damn near 100% new brake system. Only thing not to is the distribution block. But it was working before, and shoild be now.
I have bled this system a few times now. Vacuum. Reverse pressure. And the old fashioned way. Ive opened the valve for the rear, and ive left it closed. Doesnt make a difference. My problem is as soon as the truck is started, the pedal will go down when pressed. If i pump it 2-3 times, brakes are awesome. Let up, drive, same thing. Pump the pedal, awesome brakes. There is 0 air in the system when i go to bleed them. Again. All of the bleeders **** a big stream of bubble free fluid. I dont see any air bubbles in the mc when the pedal is being worked. The brakes bleed just fine, and have a great pedal, until the engine is started. Wtf. Its driving me crazy. Ideas? Remember, everything is new except the dist block, but it was working prior to me switching sheetmetal.
I have bled this system a few times now. Vacuum. Reverse pressure. And the old fashioned way. Ive opened the valve for the rear, and ive left it closed. Doesnt make a difference. My problem is as soon as the truck is started, the pedal will go down when pressed. If i pump it 2-3 times, brakes are awesome. Let up, drive, same thing. Pump the pedal, awesome brakes. There is 0 air in the system when i go to bleed them. Again. All of the bleeders **** a big stream of bubble free fluid. I dont see any air bubbles in the mc when the pedal is being worked. The brakes bleed just fine, and have a great pedal, until the engine is started. Wtf. Its driving me crazy. Ideas? Remember, everything is new except the dist block, but it was working prior to me switching sheetmetal.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
You didn't mention if you have a power brake booster but by your description, it sounds as though you do.
If you replaced the MC, did you measure the booster output rod length (IF you have a booster) in relation to the depth of the MC, where the booster output rod engages the MC?
Procedure for adjusting the booster output rod.
http://api.viglink.com/api/click?for...FMMBAK-1r1.pdf
If you replaced the MC, did you measure the booster output rod length (IF you have a booster) in relation to the depth of the MC, where the booster output rod engages the MC?
Procedure for adjusting the booster output rod.
http://api.viglink.com/api/click?for...FMMBAK-1r1.pdf
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Junior User
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It doesnt go allll the way to the floor. But close to. Brakes still work, but not like they should. Press the pedal, let up, push the pedal again and good brakes. Pedal doesnt sink or anything at this point. I dunno what it could be. Usually when i post its because ive done everything i know to do, and went through my fsm. So maybe someone has gone through this before. I think it could be a defective mc. It was a new item from rockauto, but only $10 on clearance. My thinking of this is because i had a clutch mc do a very similar thing once.
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
I didn't see it mentioned if this is a rebuilt MC or a new one (?). I learned my lesson on using rebuilt MCs a long time ago and I only buy new ones now.
If there's no air in the system and there are no hydraulic fluid leaks and the rear brake shoes are adjusted out, the only other thing I can think of is possibly the MC is bypassing internally. Being a new/rebuilt part (if the MC has been replaced) doesn't necessarily mean the part is good. Lots of new stuff these days is bad right out of the box.
If there's no air in the system and there are no hydraulic fluid leaks and the rear brake shoes are adjusted out, the only other thing I can think of is possibly the MC is bypassing internally. Being a new/rebuilt part (if the MC has been replaced) doesn't necessarily mean the part is good. Lots of new stuff these days is bad right out of the box.
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More Turbo
Joined: Dec 2013
Posts: 647
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From: SOUTHBURY CT
It doesnt go allll the way to the floor. But close to. Brakes still work, but not like they should. Press the pedal, let up, push the pedal again and good brakes. Pedal doesnt sink or anything at this point. I dunno what it could be. Usually when i post its because ive done everything i know to do, and went through my fsm. So maybe someone has gone through this before. I think it could be a defective mc. It was a new item from rockauto, but only $10 on clearance. My thinking of this is because i had a clutch mc do a very similar thing once.
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