Front M/Cyl. will not hold pedal pressure.

Hi guys Cobra Jon here.

I have my Cobra completed for shake down and Sat. I test drove it for the first….TIME OH YEAH! It's been one year. Will have to disassemble for paint but I have built the entire car.
But any how the brakes were terrible. Originally I power bleed the fronts and rears (w/ rods disconnected) using the Power Master pump up bleeder I have used on other Cobra’s. So I put the car back up and had the wife press the pedal as I hand spun the wheels. Rears worked fine. No fronts at all.
I then worked back through all fitting connections in the front for tightness, found none of these loose. So we manually bled them, pump up then bleed. They got better, still not right. Put the power bleeder back on and this is with the M/cyl. connect rods disconnected.
Bled about 2 or 3 cups of fluid through front, some air not much. Reached in and pushed rod by hand, it was firm and holding. So reconnected rods to F & R and adjusted out.
Still had no fronts until I really pumped them also finally got brake lights I knew there was something up with this because I had all lights except them and I could connect the 2 wires from the switch together and they worked. Also the threaded rod that goes through the pedal to both M/cyl. linkages, holds firm on the right M/cyl. (rears) and goes crooked as the left M/cyl. (front) fails to hold. This would be normal due to the cyl. not holding pressure. Also has anybody brought their brake pedal up and off the floor more than it sits from the builder? To me the angle is wrong and the M/cyl. rods need to be extended.
Took pedal linkage back apart. Same scenario. Rear master firm…front mushy….????
Ideas and comments please.

Had similar issues. When bleeding, your suppose to disconnect the front master cylinder push rod from the balance bar. Then bleed the rears starting at the farthest nipple. Disconnect rod and do same for front. My pedals were way too low so I took one of the master cylinder push rod to a machine shop and had them make me a couple that were 1.5 inches longer. Need to be careful not to lengthen so much that the rod will bind when pedal is depressed.
Bob

You're correct on the disconnection sequence and I didn't follow that procedure. I just disconnected both. I will try the directions in the assembly manual (imagine that). I do believe that I will extend the master rods with long nuts and threaded rod cut to the correct length. That way I will still have adjustment and not bind them up.

Thanks, Bob

sounds like you need to adjust the balance bar too, get more pressure to the fronts. i believe that the balance bar is not preset on installation andwill require some adjustment!

Scott is correct, the balance bar needs to be adjusted. It sounds like you have all rear brakes and no or little front, that is why the brake lights don't come on unless you push hard on the pedal.

Alan

But you would think that with the balance bar completely disconneted from both masters they both would bleed out without any problems. Is this a correct presumption?

Yes but when you reconnect the rods the balance has to be set. Most setups want about 70 front 30 rear. You will have to drive the car and heat up the brakes then adjust the bias.

Thanks, good info. I'll post results soon.

Shucks.....I though having little to no brakes was just part of the Cobra driving experience!

cobrajon - You can't just cut longer threaded rods. The end that goes in the master cylinder flares out to a half ball. The master cylinder push cylinder has a concave surface that the rod pushes against. Take master off and remove spring clip and the rod will come out.
Bob

I bought some grade 8 bolts that were longer. If you don't have a milling machine or small lathe to turn the head of the bolt to the ball shape the orginal bolts have there is another way. Put the bolts in a drill press with the nut end out. Acquire a grinder with a flapper wheel. Spin the bolt with the drill press while gently using the flapper wheel to shape the bolt head to the correct size/shape. When done you can touch up with a buffing wheel to smooth out. Apply a small amount of grease on these and try them on jackstands before driving.

Made a big difference. The braking on these cars is not that great. There are other people that have tried different brake pads and maybe they will chime in.

Once you grind down ends, will grade 8 bolts rust? I made mine out of stainless steel rods.
Bob

An alternative to longer pushrods is milling longer clevises that the pushrods thread into on the pedal end.

Ok I purchased 1 5/16" SAE extension nut, cut it in half finished it, added portions of (2) 5/16 SAE bolts to one end of each nut portion. Brazed these inplace giving me about 3/4" thread and a total of one and a quater inch piece overall. Threaded this in to the U shaped pieces until they butted tight to each other. Then used the existing M/Cyl rods and threaded them into the female portion of the cut long nut with the locking nut upside this.
Last nite I did another power bleed with using my mod and the front M/cyl. rod connected and the rear rod disconnected. No air in fronts. Set up bais bar between both, once again using the mod on the rear side and VOILA!... great pedal... further from floor... pad portion of pedal angles up for better foot contact... brake lights...Made sure adjustment of bais bar gives roughly 70% front and 30 % rear. Locked everything down tight. Will drive when weather clears. Thanks for all the help and comments. I like DSWANN's take on the thrill of little or no brakes. Seems like the car picks up speed when the brake pedal goes to the floor while driving it, not good for the nerves or your drawers. Been there done that.

They shouldn't rust with the grease and the constant pushing of the pedals. The grade 8 is stronger than stainless and I just felt better knowing how hard I push on them every know and then. I also wanted a one piece setup, fewer parts = less trouble.

Almost forgot, contrary to popular belief SS will rust unless it 320 or higher. Most SS you buy unless you request will be 316, it'll rust.

dmswann seems to be like the ultimate wildman. An adrenilin junky. We'd all like to party with him someday.