still no braking

[Tman 1957]

ok here we go, i have replaced wheel cyl both front rears are ok, new master cyl good pads brakes have been adjusted all the way out till they just barely touch drum oh and yes it is drums all the way around. disconnected all metal lines and blew them out then gravity bleed through the night, bench bleed mc all good there still cannot get any kind of braking power when you pump up and then open bleeders fluid barelys trickles out. WTF this is getting old cant even get this thing to slow down wheel spin by hand much less driving this stupid thing, been going on for weeks now.

HELP PLEASE ....

 

[Keeper]

you using residual valves?

 

[Francis Blake]

I am not trying to sound like a smart xxx but are you using a helper to hold pressure on the brakes while you bleed them?

 

[Tman 1957]

Yes there are pressure valves but they are drilled out, and yes there us someone helping with the pumping of the brakes.

 

[Hotrod46]

Is the pedal getting firm when you pump it up? What are the diameters of your wheel cylinders and master cylinder? What is the ratio of your pedal? When you push the pedal, are you stroking the MC all the way that it can travel?

I have drums (39 Lincoln\modified S10) on mine with dual Wilwood master cylinders and it stops great. I do have working 10 pound residual valves in both front and rear lines.

With drums you need functioning residual valves to keep the return springs in the drums from pushing the fluid back into the MC. If not it can take 1 or 2 pumps to get the shoes out to the drums.

Also, depending on the sizes of the MC, wheel cylinders and pedal ratio, you may not be building much mechanical advantage or traveling far enough to operate the MC properly.

Mike

 

[Tman 1957]

Seems to be pushing far enough. Had it out yesterday Bench bleed checked throw is OK. Pedal is extremely hard to push

 

[gfigms]

Bad master cylinder? ... even if it is new ...

 

[Tman 1957]

would a bad MC cause a rock hard pedal

 

[409T]

Adjust the rod between your brake pedal and the master cylinder so that when your foot is off the brake, there is a little slop between the rod and the master cylinder.

 

[Hotrod46]

What MC and brakes are you using? You could have a mismatch of parts. For instance, most S10 drums have 3/4" bore wheel cylinders. If you're using them with a 1" or larger MC, then you won't have much brake on the rear. They were sized for use with power disc brakes and to keep them from locking up on pickups. Just an example, that may not be what you're runing.

You also need at least 6 to 1 ratio on your pedal, 7 or 8 to 1 would be better. The extremely hard pedal could indicate low pedal leverage or a too large MC bore or both. It could also indicate a blockage in your lines, but you have checked for that.

Mike

 

[Ma_n_Pa T]

What size piston master do you have, also what is the pedal ratio, anything larger then 1" pistion master would require a longer pedal ratio, if you replaced the wheel cyl. the problem has to be in the master or pedal ratio. One other thing you may want to look at is the shoe to drum contact, see that they are making full shoe contact on the drum. If not they may need arching or drums turned.

Is the piston in the master with (no lines hooked up) moving the full length of the pistion? If not, check to make sure you do not have pluged line ports. As long as the pistion is moving, plug the ports off as you would do to bench bleed, pedal should be rock hard with everything pluged off.

 

[Ma_n_Pa T]

Hotrod all ready covered it, I agree

 

[Tman 1957]

Adjust the rod between your brake pedal and the master cylinder so that when your foot is off the brake, there is a little slop between the rod and the master cylinder.

ok i will try that

 

[Wild Mango]

I would suspect the residual pressure valves. You say you "drilled them out". Why? You need the rp checks to maintain line pressure so the seals don't weep fluid as someone has already said. I just wonder why you drilled them out.
If you pump up on the pedal and crack a bleed valve it should whoosh but you say its a dribble which suggests an obstruction in the line.
JM2CW

 

[Tman 1957]

I drilled them out because i suspected that rust may have been the issue, car was parked in grass for several months. Ive sinced blown out all lines and there are no obstructions in them.. Just gettting a dribble out of them..

 

[2old2fast]

Start at the beginning, If you disconnect the lines at the master, what kind of flow do you have?
dave

 

[Tman 1957]

Start at the beginning, If you disconnect the lines at the master, what kind of flow do you have?
dave

what do you mean flow ?? it bench bled ok, there is no flow if you disconnect lines.

 

[Don'tCallMeJimmie]

what do you mean flow ?? it bench bled ok, there is no flow if you disconnect lines.

Point to think about here. You bench bled the master. Was it in the bracket/pedal assembly, or did you just use something to push the piston in and bleed? If you didn't use the pedal, you aren't duplicating on the bench what you're experiencing on the car.

Hard pedal, no flow, lines seem to be open.

I'd be looking at how far that pedal actually moves the MC piston. Pedal ratio still seems a likely suspect with two factors in the picture - no travel, creating the trickle you see with an open line on-car and not enough mechanical advantage over the master cylinder so you never apply sufficient pressure to the wheel cylinders/calipers (if any) to get real braking effort.

Did you notice good flow when you bench-bled?

 

[Tman 1957]

Point to think about here. You bench bled the master. Was it in the bracket/pedal assembly, or did you just use something to push the piston in and bleed? If you didn't use the pedal, you aren't duplicating on the bench what you're experiencing on the car.

Hard pedal, no flow, lines seem to be open.

I'd be looking at how far that pedal actually moves the MC piston. Pedal ratio still seems a likely suspect with two factors in the picture - no travel, creating the trickle you see with an open line on-car and not enough mechanical advantage over the master cylinder so you never apply sufficient pressure to the wheel cylinders/calipers (if any) to get real braking effort.

Did you notice good flow when you bench-bled?

real good flow

 

[2old2fast]

I don't know how you bench bled your master,I'm guessing w/ the plastic fittings & hoses that are usually included. That being the case, after you get all the bubbles out, hold 1 hose up out of the reservoir & see what kind of flow you have[should be a steady full stream] if it's more than you're seeing at the wheels, then you can proceed "down the line". Diagnosis is a step by step process, like 1 of my old boss's told me, "I'll bet you're smarter than that car!!" If possible, pic's of your m/c & pedal setup would be helpful! dave