Brake Bleeding with Valve Cap

[cv2065]

Started to bleed my brakes tonight. The good news is that I only had a small leak in the lines themselves and fixed that easily. But I did have some challenges and wanted to see if I could get a little assistance. So two things:

1. I attempted to bleed my MC. I made a little tube with fitting that goes right back into the MC to get all the air out. When I pulled the cap off of the MC, the fluid spilled out all over the place and started leaking from the main fitting so I quickly put the line back on. How does one get the return tube to sit inside the reservoir if the level of fluid is so high?

2. I have the CNC cap with the air valve on it and hooked it up to my air pump. Even though I like the 2 person pump method, the wife is a bit cranky tonight and the garage is not in her future, so I thought I would try this method to push all of the air through the MC and then out the brake lines. My bicycle pump was not registering any air and I was taking it slow, but I could hear it going in...then pop, my MC reservoir cap popped off and then I had a brake fluid party. Luckily everything is covered up with shop towels. So...obviously I had too much pressure but really hard to tell with my pump. Maybe I'll pick up a smaller hand pump tomorrow. Any tips on doing this way as I might try again...Should I have a valve already open when pushing the air into the reservoir?

Thanks!

[edwardb]

Nothing worse than brake fluid spills. Sorry to hear about that. Hopefully you got it all cleaned up before doing any damage. Responses to your points.

1. I think you're describing a "bench bleed" used to remove air from the master cylinder. But you shouldn't take the cap off the MC. Take the cap off the reservoir and remove the brake line from the MC. Then using a short piece of brake line, install into the MC outlet and route back back into the reservoir. I have a hose I made with a short piece of brake line then a plastic tube that reaches the reservoirs. You will get a few drops of fluid out of the MC connection when taking the lines on and off, but no big deal with a rag underneath to catch. Push the brake pedal down slowly a few times, and you should get a solid stream of brake fluid back into the reservoir. Then replace the temporary line with your permanent brake line. Pretty simple and shouldn't be messy. I use this process when doing the pressure bleed (point #2) although several have told me it's not necessary. I do it anyway since it's not hard and I've always gotten a hard pedal the first time.

2. Using the CNC cap only requires 4-6 PSI. It's not much. I know some guys recommend using a tire pump because they're afraid using a compressor would put in too much pressure. I don't know. A tire pump can generate a lot of pressure (way more than 4-6 PSI) especially if going into a small volume like the airspace in the reservoir. I turn the regulator on my compressor air line down to about 5 PSI, and have never had any trouble using the CNC cap. No need to open any of the bleeders first when pressurizing the reservoir. In fact, don't think that would really work right anyway. Pressurize the reservoir, go to the caliper you're bleeding, with a tube on the bleeder and into a vessel of some kind (I use a small Ball jar with a hole in the lid), open the bleeder and fluid will run out. Obviously you're looking for a solid stream without any bubbles. For the first time, especially for long runs (e.g. rear passenger side), you may have to pressurize the reservoir several times. Also for the first time, I generally go around and do all four corners twice. The second time is almost always a solid stream. But an occasional bubble comes through the second time. Just watch the level in the reservoir and don't let it run out. If so, you'll get to start over. When done, I generally fill them about 2/3 full. Now test your brakes. You should have a hard pedal and all the brakes should work. This is also where you check the brake line connections for leaks. After the initial check, I hold the pedal down hard for a minute or two and confirm it stays firm. Then check again for leaks. Maybe not a good sign you were seeing leaks before this point.

[cv2065]

Thanks for the detailed response Paul. Much appreciated! The leak I had I believe was due to the fitting not being tight enough, as I pumped the brake pedal a little to get fluid into the system. Went away once I tightened it up.

I’ll get the MC bleeding done in the morning and let you know how I fare. Thanks again!

[jrcuz]

The info I got when I called CNC also included DO NOT touch the brake pedal until you are finished.
JR

[cv2065]

The info I got when I called CNC also included DO NOT touch the brake pedal until you are finished.
JR

Thanks JR. I also read, after the fact, that you don't want the reservoir more than 3/4 full. I think that was one of my issues as well.

[cv2065]

So I rigged up a couple of lines this morning and am bench bleeding both front and back MCs at the same time. When I push on the pedal fluid comes out of both MCs, but as the brake pedal is released, air seems to be getting sucked into both lines. The lines I have in the reservoirs are submerged.

Thoughts?

[cv2065]

Update: Was able to get both MC's bled. Issue was that one of the fittings wasn't tight enough and that the return hose I had going into the reservoir was curling up at the bottom and trapping air. All good.

[Avalanche325]

A good thing to have I the garage is syringes. They are good for things like sucking out excess brake fluid, priming a carb etc.
You can also open a bleeder and let it gravity bleed the excess out. MC cap off.

Bicycle tires, for road bikes, are typically rated at 120psi. Bicycle pumps are usually high pressure / low volume.

Glad to hear that you got it done.

[cv2065]

A good thing to have I the garage is syringes. They are good for things like sucking out excess brake fluid, priming a carb etc.
You can also open a bleeder and let it gravity bleed the excess out. MC cap off.

Bicycle tires, for road bikes, are typically rated at 120psi. Bicycle pumps are usually high pressure / low volume.

Glad to hear that you got it done.

Thanks for the tips! I was considering gravity bleeding all 4 corners at the same time as I’ll be by myself today. Any issues doing that? When you say MC cap off, are you talking about the reservoir?

[Railroad]

For what it is worth, Wilwood components through out, no bench bleeding, topped off the reservoirs, opened all the bleeders, closed them as fluid began to drip, 2 man pump and bleed, watched the reservoir levels and all is done. Note there are 2 bleeder valves on top of each caliper of the Wilwoods.

[cv2065]

For what it is worth, Wilwood components through out, no bench bleeding, topped off the reservoirs, opened all the bleeders, closed them as fluid began to drip, 2 man pump and bleed, watched the reservoir levels and all is done. Note there are 2 bleeder valves on top of each caliper of the Wilwoods.

I have the regular mustang brakes that come with the kit. Since I have the Wilwood footbox, can I bleed one corner at a time or do I need to do both front and back at the same time because of the balance bar? This is why I was considering the gravity bleed..

[Railroad]

If you have front and rear reservoirs/master cylinders, it should make no difference. I would open the both bleeders on either end and let it bleed. Tighten and go the the other end. If your master cylinder push rod is adjusted right, there is a clear path from the reservoir to the caliper. Having the reservoir cap loose or off will surely improve the gravity bleed. It took about 5-10 minutes to start, having to close the bleeders. I did the pedal pump bleed on the farthest caliper on each end after the gravity bleed. I did get a little air with the pedal bleeding to finish.

[cv2065]

If you have front and rear reservoirs/master cylinders, it should make no difference. I would open the both bleeders on either end and let it bleed. Tighten and go the the other end. If your master cylinder push rod is adjusted right, there is a clear path from the reservoir to the caliper. Having the reservoir cap loose or off will surely improve the gravity bleed. It took about 5-10 minutes to start, having to close the bleeders. I did the pedal pump bleed on the farthest caliper on each end after the gravity bleed. I did get a little air with the pedal bleeding to finish.

Thanks RR. I was able to get the reads to gravity bleed, but I’m not getting any fluid to the front calipers. I verified that fluid is coming out at the tee of the pedal is depressed, but the bleeder screw is bone dry if I pull it all the way out. Do I jjust need to pump the brakes more to get the fluid in the lines or is there something else I should be looking at? The MC bled just fine earlier today.

[edwardb]

Thanks RR. I was able to get the reads to gravity bleed, but I’m not getting any fluid to the front calipers. I verified that fluid is coming out at the tee of the pedal is depressed, but the bleeder screw is bone dry if I pull it all the way out. Do I just need to pump the brakes more to get the fluid in the lines or is there something else I should be looking at? The MC bled just fine earlier today.

Sounds like you've given up on the pressure bleed with the CNC cap? How come?

[CraigS]

One problem w/ the balance bar is that, once you get one MC bled, now it's push rod goes only part way into the MC. The balance bar can only run at a certain max angle, so w/ one MC push rod not moving fully, the other push rod may not travel fully either. This is why it is often recommended to bleed both calipers on one side of the car at the same time. IE bleed RF and RR together and then bleed LF and LR together. Another problem you can have is w/ the bleeder leaking around it's threads. I often used to bleed by myself one caliper at a time w/ a clear hose from the bleeder into a clear catch bottle. That some times works but other times as you release the pedal it sucks air back into the caliper via the bleeder threads. So I found that a pedal bleed procedure where the bleeder is closed before the brake pedal is released is the only way it works. But that requires 2 people, and needing to bleed two calipers at a time actually requires 3 people. So 3-4 yrs ago I put together pressure bleeder adapter so I could pressurize the MC.
Pressure Bleeder by craig stuard, on Flickr
I have a compressor and a regulator but I recommend you go to a pet store and buy a cheap (<$20) aquarium air pump. Since I started pressure bleeding I have not had any problems getting air out, it goes relatively quickly, and I can do it by myself.

[Railroad]

Thanks RR. I was able to get the reads to gravity bleed, but I’m not getting any fluid to the front calipers. I verified that fluid is coming out at the tee of the pedal is depressed, but the bleeder screw is bone dry if I pull it all the way out. Do I jjust need to pump the brakes more to get the fluid in the lines or is there something else I should be looking at? The MC bled just fine earlier today.

I would first check to make sure the master cylinder push rod has clearance and is not pressing against the master cyl piston. This will close the hole in the master cly that the fluid will siphon into.
Make sure the cap is off the reservoir and it is full. It will go down as the flow begins.

You might tap on the lines or caliper. If you have one of those hand vacuum pumps, you could put it on the open bleeder screw. There will be some leakage by the threads, but once you get the fluid flowing, it should fill the calipers.
Let me know what you find.

[cv2065]

Sounds like you've given up on the pressure bleed with the CNC cap? How come?

Hey Paul. Thought I’d experiment a little with methods that I had not done before, like the gravity bleeding. Was really easy to do but as I’m finding out, has its shortcomings when a balance bar is used. Same with the 2 person if you have to bleed 2 sides at a time, which is one plus for the gravity bleed. Seems like the best way is the pressure method. I’ll pick up another pump today, as I don’t trust my bicycle pump.

Craig - the aquarium pump would seem to be perfect with the low amount of pressure it puts out. As I blew one of my MC tops off with the bicycle pump. Really hard to gauge pressure with that. I have the ported CNC too so I’ll give that a go again starting with the front and a smaller pump. Thanks for the info around the balance bar. I had seen a couple of posts speak to it but not in that much detail. Now I understand it a little better.

[cv2065]

I would first check to make sure the master cylinder push rod has clearance and is not pressing against the master cyl piston. This will close the hole in the master cly that the fluid will siphon into.
Make sure the cap is off the reservoir and it is full. It will go down as the flow begins.

You might tap on the lines or caliper. If you have one of those hand vacuum pumps, you could put it on the open bleeder screw. There will be some leakage by the threads, but once you get the fluid flowing, it should fill the calipers.
Let me know what you find.

I do have a hand vacuum and will keep that as an option. I’ll also verify that the MC is setup correctly. I didn’t have a problem bleeding the MC so I’m assuming that I’ve set it up correctly.

[Railroad]

I do have a hand vacuum and will keep that as an option. I’ll also verify that the MC is setup correctly. I didn’t have a problem bleeding the MC so I’m assuming that I’ve set it up correctly.

Bleeding the master cyl does not mean the push rod is properly set. Adjust it so there is no preload on the push rod. You can put excess clearance in it for bleeding if you are unsure. You can adjust to minimal clearance after bleeding.

[cv2065]

Ok...so made some progress here. I bought a small hand held bike pump. Made a world of difference in terms of feel and control when getting air into the system. I bled the fronts, rears, then fronts again. I put a little air in the system, opened the valve until no bubbles, closed and pumped more air in...did that for each side until there were no more bubbles. I had gravity bled the rears last night and didn't get too many bubbles. Rears didn't use too much fluid, but the fronts did. That said, my pedal is still a little spongy, as it has to travel quite a bit to get hard, but I do know that the calipers are grabbing as I do have resistance at each wheel when the brake pedal is pushed. I'm guessing that I need to start again as there is still air in the system?

[cv2065]

Went another round corner to corner with the pressure bleed and I'm getting no bubbles at all. The fluid drains into the bottle on each one and I give it 3 pumps each..and no bubbles. Other good news is that I've sealed up any other leaks that I had, so the system seems to be 'fluid tight' at this point. BUT, my pedal is still spongy. It doesn't go to the floor, but has a pretty good travel before it gets hard.

Is it time to bleed the MC's again? And if I do that, do I have to go back around and bleed all 4 corners again?

[BadAsp427]

I'm wondering if you have the balance bar pushing in on your rears way to soon thus causing the pedal to have to be pushed further down to get the front brakes to start pressurizing. does that make sense?

[cv2065]

I'm wondering if you have the balance bar pushing in on your rears way to soon thus causing the pedal to have to be pushed further down to get the front brakes to start pressurizing. does that make sense?

Funny you say that, as i was looking for a video that shows the balance bar setting. I thought I had reviewed one a while back and wanted to see maybe if I had this set right. Come to find out when I came in from the garage, my daughter reset my phone and everything vanished. I'm not into physically punishing my kids, but man was that a test! I'll check it out and see what I come up with. Is there a video showing the settings? The book helps, but I'm more of a visual...

[cv2065]

So I found a video from Tilten about balance bar setting. Very informative. I'll post the link below if anyone needs it. I've got my balance bar set in the middle, and both MC pushrods rods screwed into the clevices just until they poke out of the backside of the clevice. Problem is that it doesn't seem as if the front MC wants to compress like the rear MC no matter how I adjust the pushrods when I push down the brake pedal. Here's a video. The left MC is the front.



As per the video, I've screwed out the front MC to about 1/4" more than the rear MC, to compensate for the larger calipers, but same result. Is there an adjustment that I can make to the rod where it meets the MC under the boot to get it to compress like the other MC?

By the way, here's the link to the Tilton video if anyone needs it:

https://www.youtube.com/watch?v=ISLqGf0sMX0

[CraigS]

There will always be some difference in MC travel. Different size MCs and different size calipers guarantees that. You could adjust the push rod in the right MC longer. Note that your balance bar is close to perpendicular to the push rods at rest. If you make the right push rod longer, your balance bar will start at an angle and change the angle as you push the pedal. As is, lets call the angle (balance bar to push rods) at rest 90 degrees. The current angle w/ brakes fully on we will call 110 degrees. If you make the right push rod longer you could have it so the angle at rest is 80 degrees, changes to 90 as you push the pedal and moves to 100 degrees at max braking. Not being there to touch your setup I can't be sure but that balance bar angle may be more than the bar can accommodate. The left MC stops, the right MC keeps going, but at some point it can't go any further because the bar is at it's max angle. If pressure in that right MC hasn't built fully, you have a mushy feel because you are starting to bend things. One other thought, don't get too concerned at having a rock hard pedal now. We sit in a car at rest and push the heck out of the brake pedal. Some times we are pushing it harder than it will be pushed in use.

[cv2065]

Thanks Craig. I extended the right rod out a bit and I get the exact same movement out of the rod. It compresses all the way while the left one moves very little. I’d upload another video but it looks almost exactly the same. And I agree what you are saying about actual application versus sitting here pushing on the pedals.

[Tony_G]

Looks like the rear breaks need bled more. That is as long as the right side master is the rear brakes. Pressure bleed the heck out of them. Keep the reservoir from running empty.

[cv2065]

Looks like the rear breaks need bled more. That is as long as the right side master is the rear brakes. Pressure bleed the heck out of them. Keep the reservoir from running empty.

Thanks Tony. Yes, the right is the reara. I’ve gravity bled them once and pressure bled twice, with no air left it seems.

[CraigS]

I just checked through the thread again and see that you have the Mustang type brakes from FFR. I may be a little off here but it's worth an ask. As I remember those calipers adjust for pad wear when you use the park brake. Can anyone confirm? If that is the case, maybe you need to actuate the park brake 10 or 12 times.

[Tony_G]

Do you know what size your master cylinders are? Have other people used the Wilwood pedals with the Mustang brakes? And if so what size masters did they use front and rear? Have you called FFR?

I have the Wilwood pedals and the Wilwood brakes. At about 1200 miles I had my rear master fail. The pedal went very soft and the rear master had lots more travel than the front. Looked very similar to your video. If you are for sure all the air is out, maybe you have a bad rear master????

Is the rear the one that you over pressurized and popped the cap off?

[cv2065]

Do you know what size your master cylinders are? Have other people used the Wilwood pedals with the Mustang brakes? And if so what size masters did they use front and rear? Have you called FFR?

I have the Wilwood pedals and the Wilwood brakes. At about 1200 miles I had my rear master fail. The pedal went very soft and the rear master had lots more travel than the front. Looked very similar to your video. If you are for sure all the air is out, maybe you have a bad rear master????

I'm thinking I have a bad rear master as well. I tried to bleed it again and its sucking air back into the master when the pedal is released. The rear is .625 and the front is .75 I believe.