brakes go to floor

[geezer#99]

Originally Posted by K10-Kansas

I didn't but I can. Thanks for suggesting that. I'll try it tomorrow.

Before you bench bleed that new master you should check it’s the right one.
Read post #8 in this thread. You need to check the depth of the pushrod hole in the master.
Possibly it’s the source of all your symptoms.


https://67-72chevytrucks.com/vboard/...d.php?t=844976

[truckin 79]

I would check the other rubber brake lines, they are probably deteriorated and squishy like the one that burst. You made sure there is no leaking from seals in all four corners right? That being said you should be able to get brakes even with old hoses. You just sucked up a lot of air when that hose burst . Not trying to be a jerk but when you had someone in the cab pumping brakes. That person held brake pedal down and then you cracked open bleeder correct? If so just keep bleeding brakes and pedal should come around

[K10-Kansas]

Originally Posted by truckin 79

I would check the other rubber brake lines, they are probably deteriorated and squishy like the one that burst. You made sure there is no leaking from seals in all four corners right? That being said you should be able to get brakes even with old hoses. You just sucked up a lot of air when that hose burst . Not trying to be a jerk but when you had someone in the cab pumping brakes. That person held brake pedal down and then you cracked open bleeder correct? If so just keep bleeding brakes and pedal should come around

Yeah, there are no leaks anywhere and I'm not loosing any fluid from the master cylinder. Yeah, we bled them by the book.

[K10-Kansas]

Originally Posted by kipps

Definitely bench bleed the master. Otherwise, there's a pocket of air trapped in the master cylinder that can't be burped out with the brake pedal alone.

Okay thanks, will do

[K10-Kansas]

So I bought a vacuum pump and pumping it up to 20 inches of pressure. I lose all of that in 10 seconds. Does that mean my booster has a leak? Is that how this test works?

I tested the tube by itself and it held the pressure with a stopper at the other end of the tube.

[K10-Kansas]

Moving the pump to vacuum it's holding 17.5 inHg steady, no issues. Maybe that's how this test goes? Vacuum and not pressure?

[mongocanfly]

Yeah...you check with vacuum ..not pressure...
again, the booster isnt causing the issue your having..
my best guess is you have air in the system somewhere,

[K10-Kansas]

Originally Posted by mongocanfly

Yeah...you check with vacuum ..not pressure...
again, the booster isnt causing the issue your having..
my best guess is you have air in the system somewhere,

Great, thanks for that confirmation. It makes sense, based on all of the information I've gotten in this thread that the behavior would be the opposite of what I have if it were a booster. I appreciate all of the great advice from everybody I've learned a lot on this one.

[mongocanfly]

If the booster was bad it would have a very hard to press pedal, like when the engine isnt running

[K10-Kansas]

Originally Posted by geezer#99

Before you bench bleed that new master you should check it’s the right one.
Read post #8 in this thread. You need to check the depth of the pushrod hole in the master.
Possibly it’s the source of all your symptoms.


https://67-72chevytrucks.com/vboard/...d.php?t=844976

Thanks. Sounds like I'd want to make sure I have the short intermediate push rod hole for power disk/drum. I'm sure it's correct. The mechanic that put it on seemed like a good mechanic. He replaced the mc and booster because he said it had the wrong one on there when I bought the truck. It was a 71c10 cab on a 77K10 chassis so I imagine they just used the booster and mc already in the 71 C10 chassis.

When I went to the parts store and asked for a 77 k10 mc, they handed me the exact same mc that I already had.

[rick1956]

Originally Posted by kipps

Definitely bench bleed the master. Otherwise, there's a pocket of air trapped in the master cylinder that can't be burped out with the brake pedal alone.

x2.

[Chevy nutcase]

Originally Posted by K10-Kansas

I put a break bleeder hose and bottle on the bleeder nut and had someone push the brake in and out several times until there was only fluid coming from the lines starting with the nut closest to the master cylinder and working my way around.

Just to clarify, you opened the bleeder and then had someone pump the brakes? If you do this, every time the person working the brake pedal leaves off, the bleeder will suck air back into the line. Pump the brakes until resistance is felt then have them hold the pedal down, you open the bleeder, let the air or bubbly fluid escape and close it. THEN resume pumping the pedal, holding, opening and closing the bleeder however many times it takes until no air comes out. As stated earlier, start with the rear brakes. Also make sure someone didn't install a caliper upside down with the bleeders on the bottom

[Just call me Sean]

He said he bottle bled the brakes, it's even in the part you quoted. When you bottle bleed it doesn't suck in air it sucks in brake fluid.

[Chevy nutcase]

Originally Posted by Just call me Sean

He said he bottle bled the brakes, it's even in the part you quoted. When you bottle bleed it doesn't suck in air it sucks in brake fluid.

Some auto parts places just sell a bottle with a hose to catch the brake fluid so it doesn't go everywhere. The don't have the siphon tube. Idk just lending my $.02

[K10-Kansas]

Originally Posted by Chevy nutcase

Just to clarify, you opened the bleeder and then had someone pump the brakes? If you do this, every time the person working the brake pedal leaves off, the bleeder will suck air back into the line. Pump the brakes until resistance is felt then have them hold the pedal down, you open the bleeder, let the air or bubbly fluid escape and close it. THEN resume pumping the pedal, holding, opening and closing the bleeder however many times it takes until no air comes out. As stated earlier, start with the rear brakes. Also make sure someone didn't install a caliper upside down with the bleeders on the bottom

I set the bottle a foot higher that the bleeder nut so that air would go up well and if it did suck anything back it would only suck back brake fluid. Yesterday I put a bleeder vacuum pump on it and it was sucking a lot of air bubbles for like a full 5 minutes with no sign of stopping. It really seems like the lines are not solid at the Master cylinder. The lines look original and I think have been moved, removed too many times. I pulled them off yesterday and today I'm stopping at LMC on the way home to get new lines. Hopefully this fixes the issue.

[72c20customcamper]

Originally Posted by K10-Kansas

I set the bottle a foot higher that the bleeder nut so that air would go up well and if it did suck anything back it would only suck back brake fluid. Yesterday I put a bleeder vacuum pump on it and it was sucking a lot of air bubbles for like a full 5 minutes with no sign of stopping. It really seems like the lines are not solid at the Master cylinder. The lines look original and I think have been moved, removed too many times. I pulled them off yesterday and today I'm stopping at LMC on the way home to get new lines. Hopefully this fixes the issue.

I have found if you don’t put some sort of sealant on the bleeder threads the vacuum pulls bubbles from the threads . Now I’m not talking a lot just a little Teflon paste on the thread not near the blender seat . A vacuum will suck air before viscous brake fluid .

[K10-Kansas]

Originally Posted by 72c20customcamper

I have found if you don’t put some sort of sealant on the bleeder threads the vacuum pulls bubbles from the threads . Now I’m not talking a lot just a little Teflon paste on the thread not near the blender seat . A vacuum will suck air before viscous brake fluid .

Oh good to know. I didn't think of that. It would also make sense not to have the bleeder nut too loose then. Wow, i wonder if I had the bleeder nut too loose.

[Just call me Sean]

Originally Posted by Chevy nutcase

Some auto parts places just sell a bottle with a hose to catch the brake fluid so it doesn't go everywhere. The don't have the siphon tube. Idk just lending my $.02

You're the second one that said something like that, so I was just pointing it out so there was no confusion.

[mongocanfly]

Times like this is when I realize how much I like my pressure bleeder..
Hundred bucks well spent..

[K10-Kansas]

Does this look like okay pressure for the rear brakes? Looks like maybe the rear brake line is bad because it's pumping air bubbles. Or is that a part of bleeding a master cylinder?

https://youtu.be/l7hl23f5f5k

[geezer#99]

Bench bleeding involves hooking up tubing from the outlet ports back into the reservoirs.
This kit will show you the process.
You only bleed the master and nothing else.


https://shop.wilwood.com/products/ma...er-bleeder-kit

[K10-Kansas]

Originally Posted by geezer#99

Bench bleeding involves hooking up tubing from the outlet ports back into the reservoirs.
This kit will show you the process.
You only bleed the master and nothing else.


https://shop.wilwood.com/products/ma...er-bleeder-kit

That's exactly what I did right? In my video I'm showing that exact process right? If not please let me know.

My question is, is this amount or pressure/flow I'm getting good? i.e. showing that it is working as expected?

[geezer#99]

In your video I can’t see where your lines are connected to.
I assumed they might be coming from the outlet of the prop valve or elsewhere.
If I’d known their source I’d of made no comment.
Apoligies for that.

[geezer#99]

Quite a difference in air bubbles.
Which reservoir is which?

[K10-Kansas]

Originally Posted by geezer#99

In your video I can’t see where your lines are connected to.
I assumed they might be coming from the outlet of the prop valve or elsewhere.
If I’d known their source I’d of made no comment.
Apoligies for that.

Oh gotcha, yeah I see, I shot that video really close you can't see where the lines are coming from.