brake problem

[Rainer]

OK, guys I need some help:

I got a 66 Dart rear-end with orig. drum brakes and 34 Plymouth brakes in the front, pedals are also 66 Dart and I put it on a 69 Camaro dual-master-cylinder (for disc and drum), the problem is that though there seems to be no air in my system, I step throug the pedal, I need to pump 3-4 times then I get the right pressure, but when i release the pedal, and step on it again it's all gone....

I think I checked it all, and I'm sure there is no air in the system.....help me guys!!!!

sorry for my english, I hope you get what I mean?

[Missing Link]

Did you check the fluid level in both reservoirs? It may be low. (I know it sounds like a smart ass comment but I can honestly say that these are the types of things that I forget to do. http://www.jalopyjournal.com/ubbthreads/images/graemlins/crazy.gif)
If I am not mistaken you use a proportional valve when running disc brakes, yes? Might just need an adjustment. I run drum brakes all around so don't take that as gospel; I'm sure someone knows better.
Or it may be the plunger rod adjustment. Check the actuating rod on the pedal assembly.

[Rainer]

jep reservoirs are full - I've 4 drums too

[Petejoe]

Yes, In order for you to loose pedal, you must have a leak in the system somewhere. I would guess the plunger is leaking but Check your fittings, lines and wheel cylinders too. How and the heck did 34 Plymouth brakes get on that type of vehicle? http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[Rainer]

hehe - good question, but they are working well , so that's why I didn't chage it (and the money http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif)
-- I removed the drums today - no leak -- the same at all fittings - I checked them 3 times ---hmm I don't know http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif

[overspray]

Rainer, I had the same problem in my "A". My master cylinder is mounted in the frame (low). I guess new style firewall mounted (Camaro) master cylinders don't have a restricter valve in them like the old under the floor mounted ones. I bought inline restricter valves for my 2 stage drum system. They let the fluid go to the wheel but slow down the return to the master cylinder. The fast return of the fluid causes something like you are describing. If I get a chance I'll PM you a picture. I forget the brand-maybe someone else knows. overspray

[RawDeal]

bttt..please help this litte fucker http://www.jalopyjournal.com/ubbthreads/images/graemlins/wink.gif

[Dirk35]

This link might have something you overlooked. Start on page one of the brake tech.

http://www.hotrodheaven.com/tech/brakes/brakes2_index.htm
(WilWoods Brake Tech)

[Bruce Lancaster]

Did you bench bleed the master cylinder before installing it? That's vital with dual cylinders.

[Tudor]

also - adjust out the brake with the spreaders - make sure they fit the drum snuggly so you can barley turn em by hand

do you have 10 psi residule valves in line? This keeps 10 psi on the wheel cylinders so when you let off and then hop back on the brakes the shoes have not moved too far awayfrom the drum - takes the slop out so to speak

[cleatus]

Maybe the problem is that you are running a disk/drum master cylinder with an all-drum system and therefore the fluid volume is incompatible?

Also...you didn't mention if the mastercylinder is new or old. Maybe it is shot?

[stan55]

If your Master Cylinder is under floor you need to have 10 psi residual valves for drum brakes and 2 psi for disc. This keeps the fluid from running back to the master cylinder as was mentioned before.

[AnimalAin]

Three words. Residual Check Valves. Available from Speedway, Jegs, Summit, or most any other hot rod vendor. About ten bucks each, as I recall. Immediately solved a similar problem on my coupe.

[Tudor]

Straight from http://www.mpbrakes.com/mpfaqvalving.htm

There are two different uses for residual valves. The 10 lb valve is used to hold a residual pressure to the drum brakes to keep the shoes out close to the drums giving a higher firmer pedal. The 2 lb valve is used in the disc when the master cylinder is lower than the calipers to prevent back siphoning of the fluid from the master.

[RawDeal]

thanks a millon guys!!!!

@animalain. please keep in mind that a few bucks for you, is twice or 3 times the money for me here in europe, nevertheless your advice got me thinking and it's more worth than any input from the muscle-car crowd here in Austria, so thanks again