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Odd brake question.....?

shady

shady

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My pedal started going to the floor all the sudden. But if I pump it once or twice it's good. May start bleeding down again when stopped, but not always .......
And it doesn't always do it. Some times you push the pedal and it stops like it always has and holds good.

But there's no leak, system has not been opened, hasn't lost any fluid at all, so no way air could get in at the master.....:dunno:

K30 hydro boost.

I know it can't be related (can it...?)
But the same day that started it also started dieing at idle occasionally.
Never know when. I'll pull to a stop 4-5 times, push clutch, idle, then take off. Next stop, push clutch, idle falls low and it will gradually stutter and die if I don't catch it.

It gets driven about an average of once a week. Usually always perfect. Then both of these on the same day :doah:
 
Yes is by passing the front cup and the rear cup is catching it. Normally you will get a an initial firm pedal, then it begins to fade. By pumping the pedal the rear cup can make up the difference.
Time for a knew Master
 
My K30 had a similar brake problem. New hydroboost fixed it.
 
I was looking up the master,(81 k30) and for the hell of it cross referenced it with my other CC (85 C30), and they're different part numbers lol. They look identical. I would have thought they were the same.

I'll try a master first. I changed the hydrobooster once before and don't want to again if I can help it lol. Granted it was a used one so it is possible to be bad.
I would think I'd have a harder pedal though, not going to the floor and not stopping....?
 
The brake fluid has to go somewhere. If the MC is good, when the rod is pushed, the fluid will exit the MC. No matter what pushes the rod. Manual foot, or hydroboost.
If the pedal goes to the floor, and is connected to the MC's rod correctly, then either the fluid found somewhere else to go, such as a busted line or brake cylinder or there is a huge air bubble in there for the fluid to compress and move into.

Since you are not losing fluid, and the problem is not there all the time, its unlikely anything has burst or an air bubble is just moving in and out of the line.
Which pretty much leaves the MC. Something inside it is letting the fluid bypass the pistons and not go out the lines.
I have seen new MCs that were intermittent like that and were fixed by bench bleeding. Supposedly there was an air bubble in there somewhere.
I have never understood how an air bubble in a MC could cause problems sometimes. I always suspected something was sticking or not sealing properly in the new unit, and the bleeding moved it enough to free it up.
I have seen times when a new MC did not work correctly every time, and it was fixed by bench bleeding, and that made sense to me.
I had the Ford dealership replace the MC on my '79 F150 under warranty on a Friday many years ago.
Drove it to where I was going to hunt the next morning, before daylight, worked fine.
About 10 in the morning, I was driving up to the group. Hit the brakes, went right to the floor. I had a bumper on that truck almost as big as the one I have now, so I just picked out a couple of small trees and clipped them off.
No damage to the truck.
A local Ford place was open on Saturdays, so I drove there slowly and carefully using the E-Brake. I kept trying the regular brakes, and they slowly got better.
I knew the shop foreman, and I asked him to replace the MC, since the fluid level was good.
He said that since it was a warranty replacement, he had to get authorization for the second unit and could not do so until Monday.
I wanted to go hunting, so I told him I would pay the cost.
He replaced it, but told me it was probably an air bubble in the new unit and had worked its self out. I told him I was not giving that unit a second shot at me.
He asked if he could keep the old one. It would fit his truck and he needed one. Said he would bleed it well and it should be fine.
I told him sure, went back hunting. I don't think I had to replace that one again for the next 10 years.
Saw the shop foreman about two weeks later. He pointed to the body shop where his truck was getting a entire new front end, complete with condenser and radiator.
Said it was a choice between rear ending a car or a hitting a phone pole. He chose the pole. Also said that he took my MC off his truck, and smashed it with a large hammer.......
 
I changed the master yesterday. Bled it, but not the system yet. It was spongy of course, but was already better.
I'm using the old lid and gasket to make a pressure bleeder attachment.
I'll pressure bleed the system when I get a chance.
Sucks that the bubbles are way up at the beginning.
 
I'd like to see what you come up with. I have never been a fan of pressure bleeder adapters. I have always ended up with a mess.
 
Some of the screw on cap ones can leak yeah. Last one I did I had some fluid under it after. Only about an 8" spot though.

One trick is pump it until you just see seepage, then stop pumping. It's enough pressure still to do it.
I forgot the drill and tap for the lid at work :doah:
Gotta see if I have any old ones around tomorrow.
 
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