Brake Bleeding

[Terry Stapley]

I am having a heck of a time getting decent brake pedal pressure on my Shell Valley. I have done everything that I can think of.
My Cobra has two systems, a front and a rear. I started with the front and did not get much pedal pressure at all and called SV and they said to bleed both systems so the bias would not come into play. I then bled the rear system and now I have some pedal pressure but you have to pump the heck out of it to get it to feel close to correct. Any help would be greatly appreciated.
I also tried a mightyvac vacuum pump at the wheel cylinders but got more bubbles than fluid.

[thunder1]

Hi : have you tried a hand vacum pump which you can buy at any auto store i have a mighty vac. you can bleed the brakes buy yourself and you don't get brake fluied on the floor I change the brake fluied once a year start at bleeder closes to brake master cylender and go from there hope this helps

[Bruce Edwards]

Have you tried gravity bleeding them? Also you need to start with the brake the farthest away from the master. Do not over pump the pedal. That can cause air to be traped in the lines.

[chopper]

See this link:

http://store.azmusa.com/hydbrakbleed.html

I have one of these little gadgets and it saves hours when you're trying to bleed brakes. They're only about $20 from AZ Motorsports. It has a one-way check valve and lets you bleed the brakes by yourself if you need to.

Also, some of the cars have to have the nose elevated to place the master cylinders in the correct orientation to get all of the air out of them when bleeding. The ERAs are like this. When I do mine, I put the front end up as high as I can when I bleed the master cylinder. This finally got all of the air out of my brakes.

[pgermond]

Terry,

I had the same identical problem and tore my hair out trying to come up with a solution.

The cure... if you haven't already done it, disconnect the rear master cylinder rod from the pedal and bleed the front, then disconnect the front rod at the pedal, re-connect the rear to the pedal and bleed the rear (always bleed from the valve the furthest from the m/c and work toward it. I used vacum bleeders, pressure bleeders, etc. When you adjust the bias 70-80% of the pedal pressure should be on the front brakes.

Good luck.

[Roscoe]

I find gravity bleeding to be very easy and satisfactory. Tilton recommends bleeding procedure to be right side left side (or visa versa) In other words do one side first then the other, not front and back.

Go to their site and check out the docs.

Roscoe

[427 S/O]

'Speed bleeders', at your usual performance stores.

[trularin]

Generally, if you have to pump, there's air still in the system.

Keep using vac until all tghe bubbles are out.

Hope this helps

[hog]

Terry
Be sure you don't run the master cylinder dry during the bleed process. I used the mighty vac and it worked great but it does drop the fluid quickly. Bleed the longest lines first
Hog

[Terry Stapley]

Thanks for the info guys. I tried the mightyvac and got more bubble than fluid! I knew that was way too much air to be coming from inside the brake lines. I got the front of the car about 1.5 feet in the air and just kept doing it the old fashioned way. I finally got some good pedal pressure about 10 pm tonight but the first push is still way mushy. Still some air somewhere! Thanks again!

[JL1924]

Check out this site:

http://www.apexperformance.net/secur.../c76206.2.html

They sell a number of MOTIVE model pressure bleeders. I bought a model for around $89.00 that came with every adapter known to man. It is a relatively simple operation to bleed with this set up. You just use the adapter that fits the master cylinder being bleed, make sure you have a good seal, pump the handle on the unit until the prescribed pressure shows on the gauge and open the bleed screws on the calipers connected to that master, one at a time. Check to see that you don't let the pressure in the main canister drop too low. When you get a steady stream of fluid, the job is done. You don't need to touch the pedals and you can do it all alone.

Hope this is helpful

JL1924

[Robert T. Faust]

Hummm, have you tried a pressure bleeding setup? I've Corvette brakes on my car and this is the only way I'm able to do it. It consists of a cover which goes over the master cylinger, then a hose from a tank full of brake fluid and pressure connects to the cover. You are able to bleed by yourself and with the tank having all that fluid you can easily flush the lines. Here is some info on them: http://www.mytoolstore.com/kd/kdbrak01.html.

[Robert T. Faust]

Sorry, forgot to mention it is a K&D Brake bleeder.

[flipper35]

Is there a separate bleeder for the master cylinders like some of the Tilton or Wilwood systems? Could be air still in the m/c like someone up above said.

[Dave Bermani]

Terry,

Looks like you've got plenty of things to try. I also have a Shell Valley. When I got the kit I looked at the dual master cylinders with the bias bar and thought "what the hell is this?" I just had not seen that setup. Anyway, I decided to replace the two units with a single GM master cylinder. A little modification to the pedal assy bracket was needed. And I added a proportioning valve to adjust the bias.

I had some trouble bleeding the brakes too, until I found out I had to "bench bleed" the master cylinder first. I also had my rear calipers upside down with the bleed screws at the bottom. They should be at the top. Just had to be a little creative when bleeding. After the bench bleeding and much wheel cylinder bleeding I have pretty good brakes. My only "problem" now is that I've driven cars with power brakes for so long that the Cobra feels inadequate. Stops though! I'm looking at adding a power booster to solve it.

Dave

[rbray]

I had a similar problem with my EM.
I found that I hand the loops that the balance bars go through scrweed too far with the reslut that the piston in the clyinder did not have enough throw.
The fix was easy. I remove the balance bar and unscrwred the loops.
Hope this helps

[rdorman]

Terry, you need to bleed the master cylinders first. Disconnect the lines, cut a spare line in half and loop it back into the bottom of the master cylinder. Pump until no more bubbles. Reconnect lines.

Jack up one SIDE of the car. Ensure that the master cylinder piston can completely return in its bore. Make sure that the bleeders are up. Bleed the outside one first if you have two on the caliper. DO NOT OPEN THE BLEEDER SCREW TO MUCH. If you do, then you will suck air around the threads. Only open enough so that the fluid will flow.

Which is what sounds as though may have been happening. I use two 'self bleeder' bottles. A little fluid in the bottom of each bottle, put the hose on the bleeder, hang the bottles so they are higher or level than the bleeder (NOT hanging from it) on both front and rear. Pump a few times (nice and slow particuarily on the way up) with my hand (none of this jump on it like a gorilla stuff while a friend opens the bleeder and sprays fluid every where). Refill. Before the bottle is full you will be bubble free and the pedal once you close the bleeder will be like a rock!

Rick

[sideoiler10]

Have you found a solution to your spongy pedal problem? If you have, please relay it to me.

I also have a Shell Valley Motors cobra with what sounds like a similar problem. The original brakes on my car were the 9" rotors in the front and large drums on a 9" Ford rear. The brakes left a lot to be desired so I decided to upgrade to 11" rotors with large GM calipers in the front and 11" rotors with Cadillac Seville calipers(w/emergency brakes) in the rear.

I have bled and bled and rebled, including power bleeding but still cannot obtain a firm pedal. The brakes stop better than before, but I don't like the soft pedal. Sometimes it feels like I need to pump it once for it to feel properly.

It uses the separate Girling master cylinders for the front and rear systems (probably same as yours). I have checked and found that Girling makes 3 different size cylinders (pistons) that produce more volume of fluid to the calipers. I was thinking that perhaps I need to switch to a larger size piston to provide enough fluid volume to the larger calipers, but first I need to find out what size pistons are in my current Girling master cylinders.

I have contacted several Cobra assemblers but have received only limited comments. I was surprised that Shell Valley Motors couldn't help me at all. Do you have any suggestions or comments?

Thank you,

Bob

[Bruce Edwards]

The size should be cast in to the side of the master. If you went to a larger brake set up and the pedal feels better than before with the smaller brakes I am not sure what your problem could be. If your masters were to small to start with going to a larger set up would have made it worse not better.
Have you tried a quick stop to see what brakes are working or is just that they feel soft? When you say "soft pedal" do you mean it takes little effort to push it or it feels like it has air in it?

[sideoiler10]

I may have misled you. I have not changed to a larger diameter cylinder yet. I was wondering if it would help, but apparently you think it would make the situation worse.

By a soft pedal I mean it is not firm when you push down on the brakes. It feels like it has a long pedal travel and is a little spongy when you first push it down. If you release it and push it again it "pumps up". It feels like there is air in the system somewhere, but as I said earlier, I have had it power bled twice by a professional shop. The guy that did it has worked for GM for 20 years and he is a very knowledgable. I think I will obtain a brake line plug and check the front and rear systems by themselves to try to locate the problem. Maybe that will help, at least I can hopefully narrow it down to one system or the other.

Any other advice or suggestions would be appreciated.

Thank you

Bob