Trouble bleeding front calipers...
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New User
Joined: Apr 2008
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Trouble bleeding front calipers...
Hi all--
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Been in Ford trucks for a number of years, starting with a '69 F100 and now working on a '78 F150 with power brakes.<O</O
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I've been trying to improve the miserable braking situation with this truck and started by doing the following since the truck bed is currently off.<O</O
<O</O
--Replaced all brake pads/shoes, replaced the rear wheel cylinders and all hard/soft lines out to the rear.<O</O
--Replaced front calipers and both soft lines.<O</O
--Replaced master cylinder (after properly bench bleeding).<O</O
<O</O
Here's my problem: While performing the bleeding of the calipers and wheel cylinders, I keep getting bubbles at the calipers. The rear wheel cylinders have bled out fine. The bubbles I keep getting at the calipers are very small, and come out 5-6 bubbles at a time. My girlfriend and I are using the "pump-brakes-crack-open-bleed-screw" method of bleeding. This is a continuous problem and keeps on after several hours of bleeding. I've never seen air in a system so persistent before. I’ve also bled the master cylinder by cracking open the fittings with pressure on the pedal and I did get a few bubbles there, but they disappeared after a few repetitions of bleeding.
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I've been reading several of the other threads pertaining to bleeding brakes on the '79 F150s and how you have to pull some kind of pin on the proportioning valve to bleed the brakes. Does this apply to an early model '78 (round headlights)?<O</O
<O</O
Since it is the only component I haven't replaced, is it possible that the proportioning valve itself is bad and is somehow allowing air to enter the system? Also, does it strike anyone that those wonderful looped brake lines under the master cylinder are ideal for holding air bubbles?<O</O
<O</O
Anyway, I’d appreciate any help or suggestions anyone could offer.<O</O
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Thanks--<O</O
Dave<O</O
<O
</OBeen in Ford trucks for a number of years, starting with a '69 F100 and now working on a '78 F150 with power brakes.<O
</O<O
</OI've been trying to improve the miserable braking situation with this truck and started by doing the following since the truck bed is currently off.<O
</O<O
</O--Replaced all brake pads/shoes, replaced the rear wheel cylinders and all hard/soft lines out to the rear.<O
</O--Replaced front calipers and both soft lines.<O
</O--Replaced master cylinder (after properly bench bleeding).<O
</O<O
</OHere's my problem: While performing the bleeding of the calipers and wheel cylinders, I keep getting bubbles at the calipers. The rear wheel cylinders have bled out fine. The bubbles I keep getting at the calipers are very small, and come out 5-6 bubbles at a time. My girlfriend and I are using the "pump-brakes-crack-open-bleed-screw" method of bleeding. This is a continuous problem and keeps on after several hours of bleeding. I've never seen air in a system so persistent before. I’ve also bled the master cylinder by cracking open the fittings with pressure on the pedal and I did get a few bubbles there, but they disappeared after a few repetitions of bleeding.
<O
</O<O
</OI've been reading several of the other threads pertaining to bleeding brakes on the '79 F150s and how you have to pull some kind of pin on the proportioning valve to bleed the brakes. Does this apply to an early model '78 (round headlights)?<O
</O<O
</OSince it is the only component I haven't replaced, is it possible that the proportioning valve itself is bad and is somehow allowing air to enter the system? Also, does it strike anyone that those wonderful looped brake lines under the master cylinder are ideal for holding air bubbles?<O
</O<O
</OAnyway, I’d appreciate any help or suggestions anyone could offer.<O
</O<O
</OThanks--<O
</ODave<O
</O
Senior User
Joined: Aug 2007
Posts: 448
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From: Winnfield,La.
You proportioning valve is stuck common with Fords and people who never flush the brake fluid! The valve has a pin at one side of it try to push and pull the pin light taps with a small hammer and some one to step on the brake, see if it moves keep repeating that till it frees up. or by a new one. If you are like me I went for the adjustable valve, that plunger is what lites up the brake warning light. you might even have some rust trash in the port going to the calipers. to bleed the front I just hook up my catch bottle with the hose to the bottom and watch for bubbles, no pumping.
Thread Starter
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New User
Joined: Apr 2008
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Thanks for the replies!
Yes, the calipers are on the correct side, and I used the new crush washers that came with the calipers. Everything is tightened as it should be. I ordered a new proportioning valve on Monday night and it should be here today or tomorrow. That's the only component (other than the front hard lines) that I haven't replaced. I'll let you guys know whether or not this helps.
Thanks--
Dave
Yes, the calipers are on the correct side, and I used the new crush washers that came with the calipers. Everything is tightened as it should be. I ordered a new proportioning valve on Monday night and it should be here today or tomorrow. That's the only component (other than the front hard lines) that I haven't replaced. I'll let you guys know whether or not this helps.
Thanks--
Dave
