Hot Rods WOW--- Where did the brakes go?

OK-- I know this has been a topic many times but now I want it to be all about MeMeMe--- The 40 Ford coupe has been on the lift for three weeks and I have zero hair to pull out. What I have is a pretty decent looking coupe with big and littles on steel wheels, a little drop up front.. Heck, isn't that all a 40 needs? So-- Just because someone before me thought it needed power did disc, it has them. GM style dual master under the floor - YEP, master booster is lower than the calipers. GM rear calipers, Mustang II stuff up front. I have 2psi residual valves one up front and one to the rear.. And a proportioning valve on the rears. 6:1 pedal ratio. all TCI stuff. Stainless lines and fittings. All new. Got the car one of the rear calipers "looked" a but wet, so I replace all of them.
NOW--- bleeding brakes using the bottle and hose-- zero bubbles... it don't take long and the rear calipers back off and the soft pedal goes to the floor---- I replaced the residual valves-- Tried again-- same soft pedal goes to floor.. Replace the M/C-- same deal soft pedal goes to floor.. I checked pedal travel to see if I had full pushrod travel so the M/C was going all the way to the bottom and returning all the way to the top-- Yep-- Plenty of travel. Checked clearance M/C to booster too. What Next?

 

so brakes worked when you bought it? the "new" calipers, explain new, new second hand , new Chinese, new GM or???

 

I see more brake problems with 4-wheel disc conversions here. Is the master correct for disc-disc? How old is the master, it may be the problem. Did it ever have a decent pedal?

 

All new parts. I think this chassis is an out of the box TCI unit... Looks like one of theirs. NEW owner bought the car out of an estate deal. Drove the car and found the brake pedal position was way too high, he missed the pedal when he went for the pedal. I cut off the boss the pedal was bolted to, turned it over and welded it back on so the pedal was lower.. NO change to the entire pedal set up at all.. just dropped the actual foot pad. I never drove the car at all until changing dropping the pad lower. I CAN get a harder pedal if I apply the parking brake-- So that tells me the rear calipers are what is bleeding back. Front wheels have a slight drag like discs normally do. Rears nope.

 

Replaced with rebuilt calipers from NAPA after seeing the one rear had been damp. NO aftermarket chrome plated stuff-- I know better than that. But hard to know where parts come from these days...

 

Someone above asked if you were sure if you had a disk/disk master cylinder and I didn't see a reply. If you have one that was designed for disk/drum it will not be able to supply enough volume to the rear calipers and will cause the condition that you describe.

 

Most aftermarket master cylinders you buy at the local parts house are now supplied with NO residual valves. I was told the thought here is that it is easier to supply a "fit-all" product and if there is a problem, the valves can be added. My masters have no residual valves in them. I am using 2# aftermarket inline valves.

 

YES-- Disc Disc Master 1" bore

 

Just guessing here, but if everything checked out ok as you say Then the brakes are working correctly, right?
Obviously you're missing something or the determination of things being ok is inaccurate. Go back over your work and double check it.

When crazy stuff like this happens to me it's not mysticism or bad ju-ju Magic , it's faulty methods.

Start by isolating the front and rear. That's going to give you a trail . Block front and rear both & the master should be hard as a rock. Block off the rears and confirm the fronts are working correctly. Add the rears in and see where the problem is, block left and right independent if you have to.

It's not hard to outsmart brake fluid, sometimes it makes you work for it.

 

Are you sure the residual valve going to the rear is put in facing the correct direction and not put in backwards?

 

I changed my rears to disc and had the same problem it turned out to be a bad hose going to the right side,I had a buddy step on the pedal as I watched,stupid flex hose would expand like a balloon! Replaced it and all was fine.


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I had the same issue with a disc/drum set up I have. I bled the brakes and found that the pressure was not releasing when I took my foot off the pedal. The brake hoses were the culprit. The flexible lines were cheap knock offs and had failed, only allowing the fluid to return to the master cylinder slowly. I had a soft pedal no matter how many times or ways I bled the system, until I replaced my braided flex lines with rubber lines.

 

Yep-- Residual valve has the flow direction arrow-- point the right way-- I also tried one of my spares, then a new out of box one-- ALSO did not like the looks of a few of the tube flares so I got out my stainless tube and made replacements using my super good flaring tool from one of the big guys that I am not sure if I should name-- BUT WOW-- what a great tool!
I have isolated front and rear. Problem is the rear.

 

Did you Isolate left and right ?

 

Flex lines are all braided stainless. I don't care for them, but that is what was there when I first got under the car. I know that these can be a problem. I need to watch and see if I can detect any swelling of these hoses

 

No- but both left and right bleed off.

 

Sure sounds like air in the system.You could always try back bleeding it,that will often cure the problem.

 

Do you have those "through the frame" brake line bulkhead fittings? I've read some of them can trap an air pocket inside of them...instant soft pedal.

 

Any malfunction in the rear circuit after the RPV will let both bleed off.
If you were to break it on the right, the left will also or visa versa.
If you break it Before the RPV both left and right will bleed off.
Break it at the master and both will bleed off till only 2lbs remain in the line. If 2lbs isn't enough to stop the caliper piston retraction You could try a 10lb in line RPV since you've tried everything else.

 

Calipers on the correct sides so that the bleeders are the high points? If the bleeders are on the bottom section you will never get the air out.

Oh yeah...if the rear calipers are the WS6 trans Am or Cadillac style that rotates the piston to activate the hand brake, you need to be using the handbrake as it adjusts the caliper for pad wear.

 

Good point!
, I've seen some where they are mounted in such a way they need to removed and bled with a piece of wood to sub for the rotor then reinstalled on the brackets even though the bleeders are up- they aren't at the top

 

yep-- bleeders to the top. No bulkhead fittings. I'm gunna sleep on all this.. I had this problem once years ago-- Had to keep bleeding-- Could still be air in the tube as it goes up over the rear axle. Been bleeding with tube and bottle method. Am thinking about going to a 1 1/8" master after this one more round of bleeding and re-thinking. Yep, Hakerbilt on the WS6 calipers has a good point as well.. Those calipers do need to seat in.. I did apply the park brake a few times--- Will do it MORE in the morning.
Thanks All! And Good Nite!

 

You said it had power brakes, I'd go with a 1 1/8 master, I also think you have a problem with air, my last car was an absolute bastard to finally bleed, musta ran a quart of fluid through it. It's difficult to bleed on your own, I use a vaccum method, pull the bleeders, wrap them thick with Teflon, reinstall and pull a vaccum on the bleeder, the Teflon stops the air sucking past the threads on the screws.

 

*2 on the winding out pistons - 20 good pulls on the parking brake should fix that.
*2 on the 1 1/8" master too.

Not seen any mention of bench bleeding the master.

Chris

 

What do you mean by tube and bottle method of bleeding?

If that's where you stick a tube over the loose bleeder screw- well that method sucks air past the bleeder threads.

 

calipers with the e brake can be a royal pain to blead i bet you still have air in them

 

A 6:1 pedal ratio is too much for a most power brakes (normally 3-4:1) so are you sure the pedal is not running out of travel before the master cylinder bottoms out? A good bleed will be questionable/not attainable if the master cannot be fully stroked.
When checking the booster push rod to master clearance, full vacuum should be applied for proper push rod positioning, and the actual clearance is normally 1/32"-1/16"., unless otherwise specified.

 

I'll probably get a lot of criticism for this. I have bled brakes for years, trying every which way. On you tube, a simple garden sprayer is converted to a pressure bleeder. Very slick. The biggest problem is farting around with a MC cap. I have tried the Mighty Vac method, Phoenix type of bleeding, helper pumping the brake pedal. The garden prayer is slicker than snot on a door knob.

 

While the concept of pressure bleeding is the best, the method of using a "garden sprayer" not so much. The last thing you want to do is pressurize air/possible moisture into brake fluid. Spend some money on a proper brake pressure bladder-type bleeder if doing occasional bleeding and/or fluid flushing, or find a friend or shop with the proper bleeder. I know....these frigin sprayer bleeders are even sold by some brake suppliers, but that doesn't make their use correct for brake fluid bleeding, IMO.

 

My buddy just went thru this on


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